[904] | 1 | <!-- ******************************************************** --> |
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| 2 | <!-- --> |
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| 3 | <!-- [History] --> |
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| 4 | <!-- Changed by: Katsuya Amako, 30-Jul-1998 --> |
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| 5 | <!-- Proof read by: Joe Chuma, 29-Jun-1999 --> |
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| 6 | <!-- Converted to DocBook: Katsuya Amako, Aug-2006 --> |
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| 7 | <!-- --> |
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| 8 | <!-- ******************************************************** --> |
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| 9 | |
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| 10 | |
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| 11 | <!-- ******************* Section (Level#1) ****************** --> |
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| 12 | <sect1 id="sect.PhysProc"> |
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| 13 | <title> |
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| 14 | Physics Processes |
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| 15 | </title> |
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| 16 | |
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| 17 | <para> |
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| 18 | Physics processes describe how particles interact with a |
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| 19 | material. Seven major categories of processes are provided by |
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| 20 | Geant4: |
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| 21 | |
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| 22 | <orderedlist spacing="compact"> |
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| 23 | <listitem><para> |
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| 24 | <link linkend="sect.PhysProc.EleMag"> |
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| 25 | electromagnetic |
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| 26 | </link> |
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| 27 | , |
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| 28 | </para></listitem> |
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| 29 | <listitem><para> |
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| 30 | <link linkend="sect.PhysProc.Had"> |
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| 31 | hadronic |
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| 32 | </link> |
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| 33 | , |
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| 34 | </para></listitem> |
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| 35 | <listitem><para> |
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| 36 | <link linkend="sect.PhysProc.Decay"> |
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| 37 | decay |
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| 38 | </link> |
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| 39 | , |
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| 40 | </para></listitem> |
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| 41 | <listitem><para> |
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| 42 | <link linkend="sect.PhysProc.PhotoHad"> |
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| 43 | photolepton-hadron |
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| 44 | </link> |
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| 45 | , |
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| 46 | </para></listitem> |
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| 47 | <listitem><para> |
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| 48 | <link linkend="sect.PhysProc.Photo"> |
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| 49 | optical |
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| 50 | </link> |
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| 51 | , |
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| 52 | </para></listitem> |
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| 53 | <listitem><para> |
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| 54 | <link linkend="sect.PhysProc.Param"> |
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| 55 | parameterization |
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| 56 | </link> |
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| 57 | and |
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| 58 | </para></listitem> |
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| 59 | <listitem><para> |
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| 60 | <link linkend="sect.PhysProc.Trans"> |
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| 61 | transportation |
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| 62 | </link> |
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| 63 | . |
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| 64 | </para></listitem> |
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| 65 | </orderedlist> |
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| 66 | </para> |
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| 67 | |
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| 68 | <para> |
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| 69 | The generalization and abstraction of physics processes is a key |
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| 70 | issue in the design of Geant4. All physics processes are treated in |
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| 71 | the same manner from the tracking point of view. The Geant4 |
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| 72 | approach enables anyone to create a process and assign it to a |
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| 73 | particle type. This openness should allow the creation of processes |
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| 74 | for novel, domain-specific or customised purposes by individuals or |
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| 75 | groups of users. |
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| 76 | </para> |
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| 77 | |
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| 78 | <para> |
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| 79 | Each process has two groups of methods which play an important |
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| 80 | role in tracking, <literal>GetPhysicalInteractionLength</literal> (GPIL) and |
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| 81 | <literal>DoIt</literal>. The GPIL method gives the step length from the |
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| 82 | current space-time point to the next space-time point. It does this |
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| 83 | by calculating the probability of interaction based on the |
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| 84 | process's cross section information. At the end of this step the |
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| 85 | <literal>DoIt</literal> method should be invoked. The <literal>DoIt</literal> method |
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| 86 | implements the details of the interaction, changing the particle's |
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| 87 | energy, momentum, direction and position, and producing secondary |
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| 88 | tracks if required. These changes are recorded as |
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| 89 | <emphasis>G4VParticleChange</emphasis> objects(see |
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| 90 | <link linkend="brhead.PhysProc.PrtChng"> |
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| 91 | Particle Change</link>). |
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| 92 | </para> |
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| 93 | |
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| 94 | <!-- ******* Bridgehead ******* --> |
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| 95 | <bridgehead renderas='sect4'> |
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| 96 | G4VProcess |
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| 97 | </bridgehead> |
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| 98 | |
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| 99 | <para> |
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| 100 | <emphasis>G4VProcess</emphasis> is the base class for all physics processes. |
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| 101 | Each physics process must implement virtual methods of |
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| 102 | <emphasis>G4VProcess</emphasis> which describe the interaction (DoIt) and |
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| 103 | determine when an interaction should occur (GPIL). In order to |
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| 104 | accommodate various types of interactions <emphasis>G4VProcess</emphasis> |
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| 105 | provides three <literal>DoIt</literal> methods: |
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| 106 | |
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| 107 | <itemizedlist spacing="compact"> |
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| 108 | <listitem><para> |
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| 109 | <literal>G4VParticleChange* AlongStepDoIt( const G4Track& track, |
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| 110 | const G4Step& stepData )</literal> |
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| 111 | <para> |
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| 112 | This method is invoked while <emphasis>G4SteppingManager</emphasis> is |
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| 113 | transporting a particle through one step. The corresponding |
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| 114 | <literal>AlongStepDoIt</literal> for each defined process is applied for |
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| 115 | every step regardless of which process produces the minimum step |
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| 116 | length. Each resulting change to the track information is recorded |
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| 117 | and accumulated in <emphasis>G4Step</emphasis>. After all processes have been |
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| 118 | invoked, changes due to <literal>AlongStepDoIt</literal> are applied to |
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| 119 | <emphasis>G4Track</emphasis>, including the particle relocation and the safety |
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| 120 | update. Note that after the invocation of <literal>AlongStepDoIt</literal>, |
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| 121 | the endpoint of the <emphasis>G4Track</emphasis> object is in a new volume if the |
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| 122 | step was limited by a geometric boundary. In order to obtain |
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| 123 | information about the old volume, <emphasis>G4Step</emphasis> must be accessed, |
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| 124 | since it contains information about both endpoints of a step. |
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| 125 | </para> |
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| 126 | </para></listitem> |
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| 127 | <listitem><para> |
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| 128 | <literal>G4VParticleChange* PostStepDoIt( const G4Track& track, |
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| 129 | const G4Step& stepData )</literal> |
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| 130 | <para> |
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| 131 | This method is invoked at the end point of a step, only if its |
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| 132 | process has produced the minimum step length, or if the process is |
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| 133 | forced to occur. <emphasis>G4Track</emphasis> will be updated after each |
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| 134 | invocation of <literal>PostStepDoIt</literal>, in contrast to the |
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| 135 | <literal>AlongStepDoIt</literal> method. |
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| 136 | </para> |
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| 137 | </para></listitem> |
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| 138 | <listitem><para> |
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| 139 | <literal>G4VParticleChange* AtRestDoIt( const G4Track& track, |
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| 140 | const G4Step& stepData )</literal> |
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| 141 | <para> |
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| 142 | This method is invoked only for stopped particles, and only if |
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| 143 | its process produced the minimum step length or the process is |
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| 144 | forced to occur. |
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| 145 | </para> |
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| 146 | </para></listitem> |
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| 147 | </itemizedlist> |
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| 148 | </para> |
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| 149 | |
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| 150 | <para> |
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| 151 | For each of the above <literal>DoIt</literal> methods <emphasis>G4VProcess</emphasis> |
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| 152 | provides a corresponding pure virtual GPIL method: |
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| 153 | |
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| 154 | <itemizedlist spacing="compact"> |
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| 155 | <listitem><para> |
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| 156 | <literal>G4double PostStepGetPhysicalInteractionLength( const |
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| 157 | G4Track& track, G4double previousStepSize, G4ForceCondition* |
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| 158 | condition )</literal> |
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| 159 | <para> |
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| 160 | This method generates the step length allowed by its process. It |
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| 161 | also provides a flag to force the interaction to occur regardless |
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| 162 | of its step length. |
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| 163 | </para> |
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| 164 | </para></listitem> |
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| 165 | <listitem><para> |
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| 166 | <literal>G4double AlongStepGetPhysicalInteractionLength( const |
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| 167 | G4Track& track, G4double previousStepSize, G4double |
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| 168 | currentMinimumStep, G4double& proposedSafety, G4GPILSelection* |
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| 169 | selection )</literal> |
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| 170 | <para> |
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| 171 | This method generates the step length allowed by its process. |
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| 172 | </para> |
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| 173 | </para></listitem> |
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| 174 | <listitem><para> |
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| 175 | <literal>G4double AtRestGetPhysicalInteractionLength( const |
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| 176 | G4Track& track, G4ForceCondition* condition )</literal> |
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| 177 | <para> |
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| 178 | This method generates the step length in time allowed by its |
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| 179 | process. It also provides a flag to force the interaction to occur |
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| 180 | regardless of its step length. |
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| 181 | </para> |
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| 182 | </para></listitem> |
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| 183 | </itemizedlist> |
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| 184 | </para> |
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| 185 | |
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| 186 | <para> |
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| 187 | Other pure virtual methods in <emphasis>G4VProcess</emphasis> follow: |
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| 188 | |
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| 189 | <itemizedlist spacing="compact"> |
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| 190 | <listitem><para> |
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| 191 | <literal>virtual G4bool IsApplicable(const |
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| 192 | G4ParticleDefinition&)</literal> |
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| 193 | <para> |
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| 194 | returns true if this process object is applicable to the |
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| 195 | particle type. |
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| 196 | </para> |
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| 197 | </para></listitem> |
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| 198 | <listitem><para> |
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| 199 | <literal>virtual void PreparePhysicsTable(const |
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| 200 | G4ParticleDefinition&)</literal> and |
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| 201 | </para></listitem> |
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| 202 | <listitem><para> |
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| 203 | <literal>virtual void BuildPhysicsTable(const |
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| 204 | G4ParticleDefinition&)</literal> |
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| 205 | <para> |
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| 206 | is messaged by the process manager, whenever cross section |
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| 207 | tables should be prepared and rebuilt due to changing cut-off |
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| 208 | values. It is not mandatory if the process is not affected by |
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| 209 | cut-off values. |
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| 210 | </para> |
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| 211 | </para></listitem> |
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| 212 | <listitem><para> |
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| 213 | <literal>virtual void StartTracking()</literal> and |
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| 214 | </para></listitem> |
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| 215 | <listitem><para> |
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| 216 | <literal>virtual void EndTracking()</literal> |
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| 217 | <para> |
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| 218 | are messaged by the tracking manager at the beginning and end of |
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| 219 | tracking the current track. |
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| 220 | </para> |
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| 221 | </para></listitem> |
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| 222 | </itemizedlist> |
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| 223 | </para> |
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| 224 | |
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| 225 | |
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| 226 | <!-- ******* Bridgehead ******* --> |
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| 227 | <bridgehead renderas='sect4'> |
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| 228 | Other base classes for processes |
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| 229 | </bridgehead> |
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| 230 | |
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| 231 | <para> |
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| 232 | Specialized processes may be derived from seven additional |
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| 233 | virtual base classes which are themselves derived from |
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| 234 | <emphasis>G4VProcess</emphasis>. Three of these classes are used for simple |
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| 235 | processes: |
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| 236 | |
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| 237 | <variablelist> |
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| 238 | <varlistentry> |
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| 239 | <term><emphasis>G4VRestProcess</emphasis></term> |
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| 240 | <listitem> |
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| 241 | <para> |
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| 242 | Processes using only the <literal>AtRestDoIt</literal> method. |
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| 243 | </para> |
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| 244 | <para> |
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| 245 | example: neutron capture |
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| 246 | </para> |
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| 247 | </listitem> |
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| 248 | </varlistentry> |
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| 249 | <varlistentry> |
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| 250 | <term><emphasis>G4VDiscreteProcess</emphasis></term> |
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| 251 | <listitem> |
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| 252 | <para> |
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| 253 | Processes using only the <literal>PostStepDoIt</literal> method. |
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| 254 | </para> |
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| 255 | <para> |
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| 256 | example: compton scattering, hadron inelastic interaction |
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| 257 | </para> |
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| 258 | </listitem> |
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| 259 | </varlistentry> |
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| 260 | </variablelist> |
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| 261 | </para> |
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| 262 | |
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| 263 | <para> |
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| 264 | The other four classes are provided for rather complex |
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| 265 | processes: |
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| 266 | |
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| 267 | <variablelist> |
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| 268 | <varlistentry> |
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| 269 | <term><emphasis>G4VContinuousDiscreteProcess</emphasis></term> |
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| 270 | <listitem> |
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| 271 | <para> |
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| 272 | Processes using both <literal>AlongStepDoIt</literal> and |
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| 273 | <literal>PostStepDoIt</literal> methods. |
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| 274 | </para> |
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| 275 | <para> |
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| 276 | example: transportation, ionisation(energy loss and delta ray) |
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| 277 | </para> |
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| 278 | </listitem> |
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| 279 | </varlistentry> |
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| 280 | <varlistentry> |
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| 281 | <term><emphasis>G4VRestDiscreteProcess</emphasis></term> |
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| 282 | <listitem> |
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| 283 | <para> |
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| 284 | Processes using both <literal>AtRestDoIt</literal> and |
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| 285 | <literal>PostStepDoIt</literal> methods. |
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| 286 | </para> |
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| 287 | <para> |
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| 288 | example: positron annihilation, decay (both in flight and at rest) |
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| 289 | </para> |
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| 290 | </listitem> |
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| 291 | </varlistentry> |
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| 292 | <varlistentry> |
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| 293 | <term><emphasis>G4VRestContinuousProcess</emphasis></term> |
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| 294 | <listitem> |
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| 295 | <para> |
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| 296 | Processes using both <literal>AtRestDoIt</literal> and |
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| 297 | <literal>AlongStepDoIt</literal> methods. |
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| 298 | </para> |
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| 299 | </listitem> |
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| 300 | </varlistentry> |
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| 301 | <varlistentry> |
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| 302 | <term><emphasis>G4VRestContinuousDiscreteProcess</emphasis></term> |
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| 303 | <listitem> |
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| 304 | <para> |
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| 305 | Processes using <literal>AtRestDoIt</literal>, |
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| 306 | <literal>AlongStepDoIt and</literal> PostStepDoIt methods. |
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| 307 | </para> |
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| 308 | </listitem> |
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| 309 | </varlistentry> |
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| 310 | </variablelist> |
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| 311 | </para> |
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| 312 | |
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| 313 | <!-- ******* Bridgehead ******* --> |
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| 314 | <bridgehead renderas='sect4' id="brhead.PhysProc.PrtChng"> |
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| 315 | Particle change |
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| 316 | </bridgehead> |
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| 317 | |
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| 318 | <para> |
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| 319 | <emphasis>G4VParticleChange</emphasis> and its descendants are used to store |
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| 320 | the final state information of the track, including secondary |
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| 321 | tracks, which has been generated by the <literal>DoIt</literal> methods. The |
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| 322 | instance of <emphasis>G4VParticleChange</emphasis> is the only object whose |
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| 323 | information is updated by the physics processes, hence it is |
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| 324 | responsible for updating the step. The stepping manager collects |
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| 325 | secondary tracks and only sends requests via particle change to |
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| 326 | update <emphasis>G4Step</emphasis>. |
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| 327 | </para> |
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| 328 | |
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| 329 | <para> |
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| 330 | <emphasis>G4VParticleChange</emphasis> is introduced as an abstract class. It |
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| 331 | has a minimal set of methods for updating <emphasis>G4Step</emphasis> and |
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| 332 | handling secondaries. A physics process can therefore define its |
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| 333 | own particle change derived from <emphasis>G4VParticleChange</emphasis>. Three |
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| 334 | pure virtual methods are provided, |
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| 335 | |
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| 336 | <itemizedlist spacing="compact"> |
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| 337 | <listitem><para> |
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| 338 | <literal>virtual G4Step* UpdateStepForAtRest( G4Step* step)</literal>, |
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| 339 | </para></listitem> |
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| 340 | <listitem><para> |
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| 341 | <literal>virtual G4Step* UpdateStepForAlongStep( G4Step* step )</literal> |
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| 342 | and |
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| 343 | </para></listitem> |
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| 344 | <listitem><para> |
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| 345 | <literal>virtual G4Step* UpdateStepForPostStep( G4Step* step)</literal>, |
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| 346 | </para></listitem> |
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| 347 | </itemizedlist> |
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| 348 | |
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| 349 | which correspond to the three <literal>DoIt</literal> methods of |
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| 350 | <emphasis>G4VProcess</emphasis>. Each derived class should implement these |
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| 351 | methods. |
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| 352 | </para> |
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| 353 | |
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| 354 | |
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| 355 | <!-- ******************* Section (Level#2) ****************** --> |
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| 356 | <sect2 id="sect.PhysProc.EleMag"> |
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| 357 | <title> |
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| 358 | Electromagnetic Interactions |
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| 359 | </title> |
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| 360 | |
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| 361 | <para> |
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[921] | 362 | This section summarizes the electromagnetic (EM) physics processes which |
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| 363 | are provided with Geant4. Extended information are avalable at EM web |
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| 364 | <ulink url="http://geant4.web.cern.ch/geant4/collaboration/EMindex.shtml"> |
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| 365 | <emphasis role="bold">pages</emphasis></ulink>. |
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| 366 | For details on the implementation of these |
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[904] | 367 | processes please refer to the |
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| 368 | <ulink url="http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/PhysicsReferenceManual/html/PhysicsReferenceManual.html"> |
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| 369 | <emphasis role="bold">Physics Reference Manual</emphasis></ulink>. |
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| 370 | </para> |
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| 371 | |
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| 372 | <!-- ******************* Section (Level#3) ****************** --> |
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| 373 | <sect3 id="sect.PhysProc.EleMag.Stand"> |
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| 374 | <title> |
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| 375 | "Standard" Electromagnetic Processes |
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| 376 | </title> |
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| 377 | |
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| 378 | <para> |
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| 379 | The following is a summary of the standard electromagnetic |
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| 380 | processes available in Geant4. |
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| 381 | |
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| 382 | <itemizedlist spacing="compact"> |
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| 383 | <listitem><para> |
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| 384 | Photon processes |
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| 385 | <itemizedlist spacing="compact"> |
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| 386 | <listitem><para> |
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| 387 | Compton scattering (class name <emphasis>G4ComptonScattering</emphasis>) |
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| 388 | </para></listitem> |
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| 389 | <listitem><para> |
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| 390 | Gamma conversion (also called pair production, class name |
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| 391 | <emphasis>G4GammaConversion</emphasis>) |
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| 392 | </para></listitem> |
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| 393 | <listitem><para> |
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| 394 | Photo-electric effect (class name <emphasis>G4PhotoElectricEffect</emphasis>) |
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| 395 | </para></listitem> |
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| 396 | <listitem><para> |
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| 397 | Muon pair production (class name <emphasis>G4GammaConversionToMuons</emphasis>) |
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| 398 | </para></listitem> |
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| 399 | </itemizedlist> |
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| 400 | </para></listitem> |
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| 401 | <listitem><para> |
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| 402 | Electron/positron processes |
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| 403 | <itemizedlist spacing="compact"> |
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| 404 | <listitem><para> |
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| 405 | Ionisation and delta ray production (class name |
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| 406 | <emphasis>G4eIonisation</emphasis>) |
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| 407 | </para></listitem> |
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| 408 | <listitem><para> |
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| 409 | Bremsstrahlung (class name <emphasis>G4eBremsstrahlung</emphasis>) |
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| 410 | </para></listitem> |
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| 411 | <listitem><para> |
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[921] | 412 | Multiple scattering (class name <emphasis>G4eMultipleScattering</emphasis>) |
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| 413 | </para></listitem> |
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| 414 | <listitem><para> |
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[904] | 415 | Positron annihilation into two gammas (class name |
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| 416 | <emphasis>G4eplusAnnihilation</emphasis>) |
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| 417 | </para></listitem> |
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| 418 | <listitem><para> |
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| 419 | Positron annihilation into two muons (class name |
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| 420 | <emphasis>G4AnnihiToMuPair</emphasis>) |
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| 421 | </para></listitem> |
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| 422 | <listitem><para> |
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| 423 | Positron annihilation into hadrons (class name |
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| 424 | <emphasis>G4eeToHadrons</emphasis>) |
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| 425 | </para></listitem> |
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| 426 | </itemizedlist> |
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| 427 | </para></listitem> |
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| 428 | <listitem><para> |
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| 429 | Muon processes |
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| 430 | <itemizedlist spacing="compact"> |
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| 431 | <listitem><para> |
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[921] | 432 | Bremsstrahlung (class name <emphasis>G4MuBremsstrahlung</emphasis>) |
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| 433 | </para></listitem> |
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| 434 | <listitem><para> |
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[904] | 435 | Ionisation and delta ray production (class name |
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| 436 | <emphasis>G4MuIonisation</emphasis>) |
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| 437 | </para></listitem> |
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| 438 | <listitem><para> |
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[921] | 439 | Multiple scattering (class name <emphasis>G4MuMultipleScattering</emphasis>) |
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[904] | 440 | </para></listitem> |
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| 441 | <listitem><para> |
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| 442 | e+e- pair production (class name |
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| 443 | <emphasis>G4MuPairProduction</emphasis>) |
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| 444 | </para></listitem> |
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| 445 | </itemizedlist> |
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| 446 | </para></listitem> |
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| 447 | <listitem><para> |
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| 448 | Hadron/ion processes |
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| 449 | <itemizedlist spacing="compact"> |
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| 450 | <listitem><para> |
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[921] | 451 | Bremsstrahlung (class name <emphasis>G4hBremsstrahlung</emphasis>) |
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| 452 | </para></listitem> |
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| 453 | <listitem><para> |
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[904] | 454 | Ionisation (class name <emphasis>G4hIonisation</emphasis>) |
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| 455 | </para></listitem> |
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| 456 | <listitem><para> |
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[921] | 457 | e+e- pair production (class name <emphasis>G4hPairProduction</emphasis>) |
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| 458 | </para></listitem> |
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| 459 | <listitem><para> |
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[904] | 460 | Ionisation for ions (class name <emphasis>G4ionIonisation</emphasis>) |
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| 461 | </para></listitem> |
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| 462 | <listitem><para> |
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[921] | 463 | Multiple scattering (class name <emphasis>G4hMultipleScattering</emphasis>) |
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[904] | 464 | </para></listitem> |
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| 465 | <listitem><para> |
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| 466 | Ionisation for heavy exotic particles (class name |
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| 467 | <emphasis>G4hhIonisation</emphasis>) |
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| 468 | </para></listitem> |
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| 469 | <listitem><para> |
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| 470 | Ionisation for classical magnetic monopole (class name |
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| 471 | <emphasis>G4mplIonisation</emphasis>) |
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| 472 | </para></listitem> |
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| 473 | </itemizedlist> |
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| 474 | </para></listitem> |
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| 475 | <listitem><para> |
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| 476 | Coulomb scattering processes |
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| 477 | <itemizedlist spacing="compact"> |
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| 478 | <listitem><para> |
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| 479 | A general process in the sense that the same process/class |
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| 480 | is used to simulate the multiple scattering of the all charged |
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| 481 | particles (class name <emphasis>G4MultipleScattering</emphasis>) |
---|
| 482 | </para></listitem> |
---|
| 483 | <listitem><para> |
---|
| 484 | Alternative process for simulation of single Coulomb scattering |
---|
| 485 | of all charged particles (class name <emphasis>G4CoulombScattering</emphasis>) |
---|
| 486 | </para></listitem> |
---|
| 487 | <listitem><para> |
---|
| 488 | Alternative process for simulation of single Coulomb scattering |
---|
| 489 | of ions (class name <emphasis>G4ScreenedNuclearRecoil</emphasis>) |
---|
| 490 | </para></listitem> |
---|
| 491 | </itemizedlist> |
---|
| 492 | </para></listitem> |
---|
| 493 | <listitem><para> |
---|
| 494 | Processes for simulation of polarized electron and gamma beams |
---|
| 495 | <itemizedlist spacing="compact"> |
---|
| 496 | <listitem><para> |
---|
| 497 | Compton scattering of circularly polarized gamma beam on |
---|
| 498 | polarized target (class name <emphasis>G4PolarizedCompton</emphasis>) |
---|
| 499 | </para></listitem> |
---|
| 500 | <listitem><para> |
---|
| 501 | Pair production induced by circularly polarized gamma beam |
---|
| 502 | (class name <emphasis>G4PolarizedGammaConversion</emphasis>) |
---|
| 503 | </para></listitem> |
---|
| 504 | <listitem><para> |
---|
| 505 | Photo-electric effect induced by circularly polarized gamma beam |
---|
| 506 | (class name <emphasis>G4PolarizedPhotoElectricEffect</emphasis>) |
---|
| 507 | </para></listitem> |
---|
| 508 | <listitem><para> |
---|
| 509 | Bremsstrahlung of polarized electrons and positrons |
---|
| 510 | (class name <emphasis>G4ePolarizedBremsstrahlung</emphasis>) |
---|
| 511 | </para></listitem> |
---|
| 512 | <listitem><para> |
---|
| 513 | Ionisation of polarized electron and positron beam |
---|
| 514 | (class name <emphasis>G4ePolarizedIonisation</emphasis>) |
---|
| 515 | </para></listitem> |
---|
| 516 | <listitem><para> |
---|
| 517 | Annihilation of polarized positrons |
---|
| 518 | (class name <emphasis>G4eplusPolarizedAnnihilation</emphasis>) |
---|
| 519 | </para></listitem> |
---|
| 520 | </itemizedlist> |
---|
| 521 | </para></listitem> |
---|
| 522 | <listitem><para> |
---|
| 523 | Processes for simulation of X-rays and optical protons production by charged particles |
---|
| 524 | <itemizedlist spacing="compact"> |
---|
| 525 | <listitem><para> |
---|
| 526 | Synchrotron radiation (class name <emphasis>G4SynchrotronRadiation</emphasis>) |
---|
| 527 | </para></listitem> |
---|
| 528 | <listitem><para> |
---|
| 529 | Transition radiation |
---|
| 530 | (class name <emphasis>G4TransitionRadiation</emphasis>) |
---|
| 531 | </para></listitem> |
---|
| 532 | <listitem><para> |
---|
| 533 | Cerenkov radiation |
---|
| 534 | (class name <emphasis>G4Cerenkov</emphasis>) |
---|
| 535 | </para></listitem> |
---|
| 536 | <listitem><para> |
---|
| 537 | Scintillations |
---|
| 538 | (class name <emphasis>G4Scintillation</emphasis>) |
---|
| 539 | </para></listitem> |
---|
| 540 | </itemizedlist> |
---|
| 541 | </para></listitem> |
---|
| 542 | <listitem><para> |
---|
| 543 | The processes described above use physics model classes, which |
---|
| 544 | may be combined according to particle energy. It is possible to |
---|
| 545 | change the energy range over which different models are valid, and |
---|
| 546 | to apply other models specific to particle type, energy range, and |
---|
| 547 | G4Region. The following alternative models are available: |
---|
| 548 | <itemizedlist spacing="compact"> |
---|
| 549 | <listitem><para> |
---|
| 550 | Ionisation in thin absorbers (class name <emphasis>G4PAIModel</emphasis>) |
---|
| 551 | </para></listitem> |
---|
| 552 | </itemizedlist> |
---|
| 553 | </para></listitem> |
---|
| 554 | </itemizedlist> |
---|
| 555 | </para> |
---|
| 556 | |
---|
| 557 | <para> |
---|
[921] | 558 | It is recommended to use physics constructor classes provided |
---|
| 559 | with rederence physics lists ($G4INSTALL/source/physics_lists/builders): |
---|
| 560 | <itemizedlist spacing="compact"> |
---|
| 561 | <listitem><para> |
---|
| 562 | default EM physics (class name <emphasis>G4EmStandardPhysics</emphasis>) |
---|
| 563 | </para></listitem> |
---|
| 564 | <listitem><para> |
---|
| 565 | optional EM physics providing similar performance as g4 7.1p01 |
---|
| 566 | (class name <emphasis>G4EmStandardPhysics_option1</emphasis>) |
---|
| 567 | </para></listitem> |
---|
| 568 | <listitem><para> |
---|
| 569 | Experimental EM physics with enabled "ApplyCuts" option |
---|
| 570 | (class name <emphasis>G4EmStandardPhysics_option2</emphasis>) |
---|
| 571 | </para></listitem> |
---|
| 572 | <listitem><para> |
---|
| 573 | EM physics for simulation with high accuracy |
---|
| 574 | (class name <emphasis>G4EmStandardPhysics_option3</emphasis>) |
---|
| 575 | </para></listitem> |
---|
| 576 | </itemizedlist> |
---|
| 577 | Examples of the registration of these physics constructor and |
---|
| 578 | construction of alternative combinations of options are shown |
---|
| 579 | in novice and extended examples ($G4INSTALL/examples/extended/electromagnetic). |
---|
[904] | 580 | Novice and extended electromagnetic examples illustrating the use |
---|
| 581 | of electromagnetic processes are available as part of the Geant4 |
---|
| 582 | <ulink url="http://geant4.web.cern.ch/geant4/support/download.shtml"> |
---|
| 583 | release</ulink>. |
---|
| 584 | </para> |
---|
| 585 | |
---|
| 586 | <para> |
---|
| 587 | <emphasis role="bold">Options</emphasis> are available for steering the standard |
---|
| 588 | electromagnetic processes. These options may be invoked either by |
---|
| 589 | UI commands or by the interface class G4EmProcessOptions. This |
---|
| 590 | class has the following public methods: |
---|
| 591 | |
---|
| 592 | <itemizedlist spacing="compact"> |
---|
| 593 | <listitem><para> |
---|
| 594 | SetLossFluctuations(G4bool) |
---|
| 595 | </para></listitem> |
---|
| 596 | <listitem><para> |
---|
| 597 | SetSubCutoff(G4bool, const G4Region* r=0) |
---|
| 598 | </para></listitem> |
---|
| 599 | <listitem><para> |
---|
| 600 | SetIntegral(G4bool) |
---|
| 601 | </para></listitem> |
---|
| 602 | <listitem><para> |
---|
| 603 | SetMinSubRange(G4double) |
---|
| 604 | </para></listitem> |
---|
| 605 | <listitem><para> |
---|
| 606 | SetMinEnergy(G4double) |
---|
| 607 | </para></listitem> |
---|
| 608 | <listitem><para> |
---|
| 609 | SetMaxEnergy(G4double) |
---|
| 610 | </para></listitem> |
---|
| 611 | <listitem><para> |
---|
| 612 | SetMaxEnergyForCSDARange(G4double) |
---|
| 613 | </para></listitem> |
---|
| 614 | <listitem><para> |
---|
| 615 | SetMaxEnergyForMuons(G4double) |
---|
| 616 | </para></listitem> |
---|
| 617 | <listitem><para> |
---|
| 618 | SetDEDXBinning(G4int) |
---|
| 619 | </para></listitem> |
---|
| 620 | <listitem><para> |
---|
| 621 | SetDEDXBinningForCSDARange(G4int) |
---|
| 622 | </para></listitem> |
---|
| 623 | <listitem><para> |
---|
| 624 | SetLambdaBinning(G4int) |
---|
| 625 | </para></listitem> |
---|
| 626 | <listitem><para> |
---|
| 627 | SetStepFunction(G4double, G4double) |
---|
| 628 | </para></listitem> |
---|
| 629 | <listitem><para> |
---|
| 630 | SetRandomStep(G4bool) |
---|
| 631 | </para></listitem> |
---|
| 632 | <listitem><para> |
---|
| 633 | SetApplyCuts(G4bool) |
---|
| 634 | </para></listitem> |
---|
| 635 | <listitem><para> |
---|
[921] | 636 | SetSpline(G4bool) |
---|
| 637 | </para></listitem> |
---|
| 638 | <listitem><para> |
---|
[904] | 639 | SetBuildCSDARange(G4bool) |
---|
| 640 | </para></listitem> |
---|
| 641 | <listitem><para> |
---|
| 642 | SetVerbose(G4int, const G4String name= "all") |
---|
| 643 | </para></listitem> |
---|
| 644 | <listitem><para> |
---|
| 645 | SetLambdaFactor(G4double) |
---|
| 646 | </para></listitem> |
---|
| 647 | <listitem><para> |
---|
| 648 | SetLinearLossLimit(G4double) |
---|
| 649 | </para></listitem> |
---|
| 650 | <listitem><para> |
---|
| 651 | ActivateDeexcitation(G4bool val, const G4Region* r = 0) |
---|
| 652 | </para></listitem> |
---|
| 653 | <listitem><para> |
---|
| 654 | SetMscStepLimitation(G4MscStepLimitType val) |
---|
| 655 | </para></listitem> |
---|
| 656 | <listitem><para> |
---|
| 657 | SetMscLateralDisplacement(G4bool val) |
---|
| 658 | </para></listitem> |
---|
| 659 | <listitem><para> |
---|
| 660 | SetSkin(G4double) |
---|
| 661 | </para></listitem> |
---|
| 662 | <listitem><para> |
---|
| 663 | SetMscRangeFactor(G4double) |
---|
| 664 | </para></listitem> |
---|
| 665 | <listitem><para> |
---|
| 666 | SetMscGeomFactor(G4double) |
---|
| 667 | </para></listitem> |
---|
| 668 | <listitem><para> |
---|
| 669 | SetLPMFlag(G4bool) |
---|
| 670 | </para></listitem> |
---|
| 671 | <listitem><para> |
---|
| 672 | SetBremsstrahlungTh(G4double) |
---|
| 673 | </para></listitem> |
---|
| 674 | </itemizedlist> |
---|
| 675 | </para> |
---|
| 676 | |
---|
| 677 | <para> |
---|
| 678 | The corresponding UI command can be accessed in the UI subdirectory |
---|
| 679 | "/process/eLoss". The following types of step limitation by multiple scattering |
---|
| 680 | are available: |
---|
| 681 | |
---|
| 682 | <itemizedlist spacing="compact"> |
---|
| 683 | <listitem><para> |
---|
| 684 | fSimple - step limitation used in g4 7.1 version (used in QGSP_EMV Physics List) |
---|
| 685 | </para></listitem> |
---|
| 686 | <listitem><para> |
---|
| 687 | fUseSafety - default |
---|
| 688 | </para></listitem> |
---|
| 689 | <listitem><para> |
---|
| 690 | fUseDistanceToBoundary - advance method of step limitation used in EM examples, |
---|
| 691 | required parameter <emphasis>skin > 0</emphasis>, should be used for |
---|
| 692 | setup without magnetic field |
---|
| 693 | </para></listitem> |
---|
| 694 | </itemizedlist> |
---|
| 695 | </para> |
---|
| 696 | |
---|
| 697 | <para> |
---|
| 698 | <emphasis role="bold">G4EmCalculator</emphasis> is a class which provides |
---|
| 699 | access to cross sections and stopping powers. This class can be used |
---|
| 700 | anywhere in the user code provided the physics list has already been |
---|
| 701 | initialised (G4State_Idle). G4EmCalculator has "Get" methods which |
---|
| 702 | can be applied to materials for which physics tables are already |
---|
| 703 | built, and "Compute" methods which can be applied to any material |
---|
| 704 | defined in the application or existing in the Geant4 internal |
---|
| 705 | database. The public methods of this class are: |
---|
| 706 | |
---|
| 707 | <itemizedlist spacing="compact"> |
---|
| 708 | <listitem><para> |
---|
| 709 | GetDEDX(kinEnergy,particle,material,G4Region region=0) |
---|
| 710 | </para></listitem> |
---|
| 711 | <listitem><para> |
---|
| 712 | GetRangeFromRestrictedDEDX(kinEnergy,particle,material,G4Region* region=0) |
---|
| 713 | </para></listitem> |
---|
| 714 | <listitem><para> |
---|
| 715 | GetCSDARange(kinEnergy,particle,material,G4Region* region=0) |
---|
| 716 | </para></listitem> |
---|
| 717 | <listitem><para> |
---|
| 718 | GetRange(kinEnergy,particle,material,G4Region* region=0) |
---|
| 719 | </para></listitem> |
---|
| 720 | <listitem><para> |
---|
| 721 | GetKinEnergy(range,particle,material,G4Region* region=0) |
---|
| 722 | </para></listitem> |
---|
| 723 | <listitem><para> |
---|
| 724 | GetCrosSectionPerVolume(kinEnergy,particle,material,G4Region* region=0) |
---|
| 725 | </para></listitem> |
---|
| 726 | <listitem><para> |
---|
| 727 | GetMeanFreePath(kinEnergy,particle,material,G4Region* region=0) |
---|
| 728 | </para></listitem> |
---|
| 729 | <listitem><para> |
---|
| 730 | PrintDEDXTable(particle) |
---|
| 731 | </para></listitem> |
---|
| 732 | <listitem><para> |
---|
| 733 | PrintRangeTable(particle) |
---|
| 734 | </para></listitem> |
---|
| 735 | <listitem><para> |
---|
| 736 | PrintInverseRangeTable(particle) |
---|
| 737 | </para></listitem> |
---|
| 738 | <listitem><para> |
---|
| 739 | ComputeDEDX(kinEnergy,particle,process,material,cut=DBL_MAX) |
---|
| 740 | </para></listitem> |
---|
| 741 | <listitem><para> |
---|
| 742 | ComputeElectronicDEDX(kinEnergy,particle,material,cut=DBL_MAX) |
---|
| 743 | </para></listitem> |
---|
| 744 | <listitem><para> |
---|
| 745 | ComputeNuclearDEDX(kinEnergy,particle,material,cut=DBL_MAX) |
---|
| 746 | </para></listitem> |
---|
| 747 | <listitem><para> |
---|
| 748 | ComputeTotalDEDX(kinEnergy,particle,material,cut=DBL_MAX) |
---|
| 749 | </para></listitem> |
---|
| 750 | <listitem><para> |
---|
| 751 | ComputeCrosSectionPerVolume(kinEnergy,particle,process,material,cut=0) |
---|
| 752 | </para></listitem> |
---|
| 753 | <listitem><para> |
---|
| 754 | ComputeCrosSectionPerAtom(kinEnergy,particle,process,Z,A,cut=0) |
---|
| 755 | </para></listitem> |
---|
| 756 | <listitem><para> |
---|
| 757 | ComputeMeanFreePath(kinEnergy,particle,process,material,cut=0) |
---|
| 758 | </para></listitem> |
---|
| 759 | <listitem><para> |
---|
| 760 | ComputeEnergyCutFromRangeCut(range,particle,material) |
---|
| 761 | </para></listitem> |
---|
| 762 | <listitem><para> |
---|
| 763 | FindParticle(const G4String&) |
---|
| 764 | </para></listitem> |
---|
| 765 | <listitem><para> |
---|
| 766 | FindMaterial(const G4String&) |
---|
| 767 | </para></listitem> |
---|
| 768 | <listitem><para> |
---|
| 769 | FindRegion(const G4String&) |
---|
| 770 | </para></listitem> |
---|
| 771 | <listitem><para> |
---|
| 772 | FindCouple(const G4Material*, const G4Region* region=0) |
---|
| 773 | </para></listitem> |
---|
| 774 | <listitem><para> |
---|
| 775 | SetVerbose(G4int) |
---|
| 776 | </para></listitem> |
---|
| 777 | </itemizedlist> |
---|
| 778 | </para> |
---|
| 779 | |
---|
| 780 | <para> |
---|
| 781 | For these interfaces, particles, materials, or processes may be |
---|
| 782 | pointers or strings with names. |
---|
| 783 | </para> |
---|
| 784 | |
---|
| 785 | </sect3> |
---|
| 786 | |
---|
| 787 | |
---|
| 788 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 789 | <sect3 id="sect.PhysProc.EleMag.LowE"> |
---|
| 790 | <title> |
---|
| 791 | Low Energy Electromagnetic Processes |
---|
| 792 | </title> |
---|
| 793 | |
---|
| 794 | <para> |
---|
[1211] | 795 | A physical interaction is described by a process class which can handle |
---|
| 796 | physics models, described by model classes. The following is a summary |
---|
| 797 | of the Low Energy Electromagnetic physics models available in Geant4. |
---|
| 798 | Further information is available in the web pages of the |
---|
| 799 | Geant4 Low Energy Electromagnetic Physics Working Group, accessible |
---|
| 800 | from the Geant4 web site, âwho we areâ section, then âworking groupsâ. |
---|
| 801 | </para> |
---|
| 802 | |
---|
| 803 | <para> |
---|
| 804 | The physics content of these models is documented in the Geant4 |
---|
[904] | 805 | <ulink url="http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/PhysicsReferenceManual/html/PhysicsReferenceManual.html"> |
---|
[1211] | 806 | Physics Reference Manual. |
---|
[904] | 807 | </ulink> |
---|
[1211] | 808 | They are based on the Livermore data library, on the |
---|
| 809 | ICRU73 data tables or on the Penelope Monte Carlo code. They adopt the |
---|
| 810 | same software design as the "standard" Geant4 electromagnetic models. |
---|
[904] | 811 | </para> |
---|
| 812 | |
---|
| 813 | <para> |
---|
[1211] | 814 | Examples of the registration of physics constructor with low-energy |
---|
| 815 | electromagnetic models are shown in Geant4 extended examples |
---|
| 816 | (<literal>$G4INSTALL/examples/extended/electromagnetic</literal>). |
---|
| 817 | Advanced examples (<literal>$G4INSTALL/examples/advanced</literal>) |
---|
| 818 | illustrate alternative instantiation of these processes. |
---|
| 819 | Both are available as part of the Geant4 release. |
---|
| 820 | </para> |
---|
| 821 | |
---|
| 822 | <para> |
---|
| 823 | To use the low energy electromagnetic models, data files need to be |
---|
| 824 | copied by the user to his/her code repository. These files are |
---|
| 825 | distributed together with Geant4. The user should set the environment |
---|
| 826 | variable G4LEDATA to the directory where he/she has copied the files. |
---|
| 827 | </para> |
---|
| 828 | |
---|
| 829 | <!-- ******************* Section (Level#4) ****************** --> |
---|
| 830 | <sect4 id="sect.PhysProc.EleMag.LowE.Livemore"> |
---|
| 831 | <title> |
---|
| 832 | Livermore based models |
---|
| 833 | </title> |
---|
| 834 | |
---|
| 835 | <para> |
---|
[904] | 836 | <itemizedlist spacing="compact"> |
---|
| 837 | <listitem><para> |
---|
[1211] | 838 | <emphasis role="bold">Photon models</emphasis> |
---|
[904] | 839 | <itemizedlist spacing="compact"> |
---|
| 840 | <listitem><para> |
---|
[1211] | 841 | Photo-electric effect (class <emphasis>G4LivermorePhotoElectricModel</emphasis>) |
---|
[904] | 842 | </para></listitem> |
---|
| 843 | <listitem><para> |
---|
[1211] | 844 | Polarized Photo-electric effect (class <emphasis>G4LivermorePolarizedPhotoElectricModel</emphasis>) |
---|
[904] | 845 | </para></listitem> |
---|
| 846 | <listitem><para> |
---|
[1211] | 847 | Compton scattering (class <emphasis>G4LivermoreComptonModel</emphasis>) |
---|
[904] | 848 | </para></listitem> |
---|
| 849 | <listitem><para> |
---|
[1211] | 850 | Polarized Compton scattering (class <emphasis>G4LivermorePolarizedComptonModel</emphasis>) |
---|
[904] | 851 | </para></listitem> |
---|
| 852 | <listitem><para> |
---|
[1211] | 853 | Rayleigh scattering (class <emphasis>G4LivermoreRayleighModel</emphasis>) |
---|
[904] | 854 | </para></listitem> |
---|
| 855 | <listitem><para> |
---|
[1211] | 856 | Polarized Rayleigh scattering (class <emphasis>G4LivermorePolarizedRayleighModel</emphasis>) |
---|
[904] | 857 | </para></listitem> |
---|
| 858 | <listitem><para> |
---|
[1211] | 859 | Gamma conversion (also called pair production, class <emphasis>G4LivermoreGammaConversionModel</emphasis>) |
---|
[904] | 860 | </para></listitem> |
---|
[1211] | 861 | <listitem><para> |
---|
| 862 | Polarized gamma conversion (class <emphasis>G4LivermorePolarizedGammaConversionModel</emphasis>) |
---|
| 863 | </para></listitem> |
---|
[904] | 864 | </itemizedlist> |
---|
| 865 | </para></listitem> |
---|
| 866 | <listitem><para> |
---|
[1211] | 867 | <emphasis role="bold">Electron models</emphasis> |
---|
[904] | 868 | <itemizedlist spacing="compact"> |
---|
| 869 | <listitem><para> |
---|
[1211] | 870 | Bremsstrahlung (class <emphasis>G4LivermoreBremsstrahlungModel</emphasis>) |
---|
[904] | 871 | </para></listitem> |
---|
[1211] | 872 | <listitem><para> |
---|
| 873 | Ionisation and delta ray production (class <emphasis>G4LivermoreIonisationModel</emphasis>) |
---|
| 874 | </para></listitem> |
---|
| 875 | </itemizedlist> |
---|
[904] | 876 | </para></listitem> |
---|
| 877 | </itemizedlist> |
---|
| 878 | </para> |
---|
| 879 | |
---|
| 880 | <para> |
---|
[1211] | 881 | Options can be set in the G4LivermorePhotoElectricModel class, that allow |
---|
| 882 | the use of alternative photoelectron angular generators: |
---|
| 883 | |
---|
| 884 | <itemizedlist spacing="compact"> |
---|
| 885 | <listitem><para> |
---|
| 886 | SetAngularGenerator(G4VPhotoElectricAngularDistribution* distribution); |
---|
| 887 | </para></listitem> |
---|
| 888 | <listitem><para> |
---|
| 889 | SetAngularGenerator(const G4String& name); |
---|
| 890 | </para></listitem> |
---|
| 891 | </itemizedlist> |
---|
[904] | 892 | </para> |
---|
| 893 | |
---|
| 894 | <para> |
---|
[1211] | 895 | Currently three angular generators are available: |
---|
| 896 | G4PhotoElectricAngularGeneratorSimple, G4PhotoElectricAngularGeneratorSauterGavrilla |
---|
| 897 | and G4PhotoElectricAngularGeneratorPolarized. |
---|
| 898 | G4PhotoElectricAngularGeneratorSauterGavrilla is selected by default. |
---|
| 899 | G4PhotoElectricAngularGeneratorSimple, G4PhotoElectricAngularGeneratorSauterGavrilla |
---|
| 900 | and G4PhotoElectricAngularGeneratorPolarized can be set using respectively the |
---|
| 901 | strings "default", "standard" and "polarized". |
---|
[904] | 902 | </para> |
---|
| 903 | |
---|
| 904 | <para> |
---|
[1211] | 905 | Options are available in the G4LivermoreBremsstrahlungModel class, that allow |
---|
| 906 | the use of alternative bremsstrahlung angular generators: |
---|
| 907 | <itemizedlist spacing="compact"> |
---|
| 908 | <listitem><para> |
---|
| 909 | SetAngularGenerator(G4VBremAngularDistribution* distribution); |
---|
| 910 | </para></listitem> |
---|
| 911 | <listitem><para> |
---|
| 912 | SetAngularGenerator(const G4String& name); |
---|
| 913 | </para></listitem> |
---|
| 914 | </itemizedlist> |
---|
| 915 | </para> |
---|
[904] | 916 | |
---|
[1211] | 917 | <para> |
---|
| 918 | Currently three angular generators are available: G4ModifiedTsai, |
---|
| 919 | 2BNGenerator and 2BSGenerator. G4ModifiedTsai is set by default, but it |
---|
| 920 | can be forced using the string "tsai". 2BNGenerator and 2BSGenerator |
---|
| 921 | can be set using the strings "2bs" and "2bn". Information regarding |
---|
| 922 | conditions of use, performance and energy |
---|
| 923 | limits of different models are available in the Physics Reference Manual . |
---|
| 924 | </para> |
---|
| 925 | |
---|
| 926 | <para> |
---|
| 927 | Other options G4LivermoreBremsstrahlungModel class are: |
---|
| 928 | |
---|
[904] | 929 | <itemizedlist spacing="compact"> |
---|
[1211] | 930 | <listitem><para> |
---|
| 931 | SetCutForLowEnSecPhotons(G4double) |
---|
| 932 | </para></listitem> |
---|
[904] | 933 | </itemizedlist> |
---|
| 934 | </para> |
---|
| 935 | |
---|
| 936 | <para> |
---|
[1211] | 937 | Options are available in the G4LivermoreIonisationModel class: |
---|
[904] | 938 | |
---|
| 939 | <itemizedlist spacing="compact"> |
---|
[1211] | 940 | <listitem><para> |
---|
| 941 | ActivateAuger(G4bool) |
---|
| 942 | </para></listitem> |
---|
| 943 | <listitem><para> |
---|
| 944 | SetCutForLowEnSecPhotons(G4double) |
---|
| 945 | </para></listitem> |
---|
| 946 | <listitem><para> |
---|
| 947 | SetCutForLowEnSecElectrons(G4double) |
---|
| 948 | </para></listitem> |
---|
[904] | 949 | </itemizedlist> |
---|
| 950 | </para> |
---|
| 951 | |
---|
[1211] | 952 | </sect4> |
---|
| 953 | |
---|
| 954 | |
---|
| 955 | <!-- ******************* Section (Level#4) ****************** --> |
---|
| 956 | <sect4 id="sect.PhysProc.EleMag.LowE.ICRU73"> |
---|
| 957 | <title> |
---|
| 958 | ICRU73 based ion model |
---|
| 959 | </title> |
---|
| 960 | |
---|
[904] | 961 | <para> |
---|
[1211] | 962 | Ionisation and delta ray production (class G4IonParametrisedLossModel) |
---|
| 963 | </para> |
---|
[904] | 964 | |
---|
[1211] | 965 | <para> |
---|
| 966 | The ion model uses ICRU 73 stopping powers, if corresponding ion-material |
---|
| 967 | combinations are covered by the ICRU 73 report (up to 1 GeV/nucleon), and |
---|
| 968 | otherwise applies a Bethe-Bloch based formalism. For compounds, ICRU 73 |
---|
| 969 | stopping powers are employed if the material name coincides with the name |
---|
| 970 | of Geant4 NIST materials (e.g. G4_WATER). Elemental materials are matched |
---|
| 971 | to the corresponding ICRU 73 stopping powers by means of the atomic number |
---|
| 972 | of the material. The material name may be arbitrary in this case. For a |
---|
| 973 | list of applicable materials, the user is referred to the ICRU 73 report. |
---|
| 974 | </para> |
---|
| 975 | |
---|
| 976 | <para> |
---|
| 977 | The model requires data files to be copied by the user to his/her code |
---|
| 978 | repository. These files are distributed together with the Geant4 release. |
---|
| 979 | The user should set the environment variable G4LEDATA to the directory where |
---|
| 980 | he/she has copied the files. |
---|
| 981 | </para> |
---|
| 982 | |
---|
| 983 | <para> |
---|
| 984 | The model is dedicated to be used with the G4ionIonisation process and its |
---|
| 985 | applicability is restricted to G4GenericIon particles. The ion model is |
---|
| 986 | not used by default by this process and must be instantiated and registered |
---|
| 987 | by the user: |
---|
| 988 | |
---|
| 989 | <informalexample> |
---|
| 990 | <programlisting> |
---|
| 991 | G4ionIonisation* ionIoni = new G4ionIonisation(); |
---|
| 992 | ionIoni -> SetEmModel(new G4IonParametrisedLossModel()); |
---|
| 993 | </programlisting> |
---|
| 994 | </informalexample> |
---|
| 995 | </para> |
---|
| 996 | |
---|
| 997 | </sect4> |
---|
| 998 | |
---|
| 999 | <!-- ******************* Section (Level#4) ****************** --> |
---|
| 1000 | <sect4 id="sect.PhysProc.EleMag.LowE.Penelope"> |
---|
| 1001 | <title> |
---|
| 1002 | Penelope based models |
---|
| 1003 | </title> |
---|
| 1004 | |
---|
| 1005 | <para> |
---|
[904] | 1006 | <itemizedlist spacing="compact"> |
---|
[1211] | 1007 | <listitem><para> |
---|
| 1008 | <emphasis role="bold">Photon models</emphasis> |
---|
| 1009 | <itemizedlist spacing="compact"> |
---|
| 1010 | <listitem><para> |
---|
| 1011 | Compton scattering (class <emphasis>G4PenelopeComptonModel</emphasis>) |
---|
| 1012 | </para></listitem> |
---|
| 1013 | <listitem><para> |
---|
| 1014 | Rayleigh scattering (class <emphasis>G4PenelopeRayleighModel</emphasis>) |
---|
| 1015 | </para></listitem> |
---|
| 1016 | <listitem><para> |
---|
| 1017 | Gamma conversion (also called pair production, class <emphasis>GPenelopeGammaConversionModel</emphasis>) |
---|
| 1018 | </para></listitem> |
---|
| 1019 | <listitem><para> |
---|
| 1020 | Photo-electric effect (class <emphasis>G4PenelopePhotoElectricModel</emphasis>) |
---|
| 1021 | </para></listitem> |
---|
| 1022 | </itemizedlist> |
---|
| 1023 | </para></listitem> |
---|
| 1024 | <listitem><para> |
---|
| 1025 | <emphasis role="bold">Electron models</emphasis> |
---|
| 1026 | <itemizedlist spacing="compact"> |
---|
| 1027 | <listitem><para> |
---|
| 1028 | Bremsstrahlung (class <emphasis>G4PenelopeBremsstrahlungModel</emphasis>) |
---|
| 1029 | </para></listitem> |
---|
| 1030 | <listitem><para> |
---|
| 1031 | Ionisation and delta ray production (class <emphasis>G4PenelopeIonisationModel</emphasis>) |
---|
| 1032 | </para></listitem> |
---|
| 1033 | </itemizedlist> |
---|
| 1034 | </para></listitem> |
---|
| 1035 | <listitem><para> |
---|
| 1036 | <emphasis role="bold">Positron models</emphasis> |
---|
| 1037 | <itemizedlist spacing="compact"> |
---|
| 1038 | <listitem><para> |
---|
| 1039 | Bremsstrahlung (class <emphasis>G4PenelopeBremsstrahlungModel</emphasis>) |
---|
| 1040 | </para></listitem> |
---|
| 1041 | <listitem><para> |
---|
| 1042 | Ionisation and delta ray production (class <emphasis>G4PenelopeIonisationModel</emphasis>) |
---|
| 1043 | </para></listitem> |
---|
| 1044 | <listitem><para> |
---|
| 1045 | Positron annihilation (class <emphasis>class G4PenelopeAnnihilationModel</emphasis>) |
---|
| 1046 | </para></listitem> |
---|
| 1047 | </itemizedlist> |
---|
| 1048 | </para></listitem> |
---|
[904] | 1049 | </itemizedlist> |
---|
| 1050 | </para> |
---|
| 1051 | |
---|
| 1052 | <para> |
---|
[1211] | 1053 | All Penelope models can be applied up to a maximum energy of 100 GeV, |
---|
| 1054 | although it is advisable not to use them above a few hundreds of MeV. |
---|
[904] | 1055 | </para> |
---|
| 1056 | |
---|
| 1057 | <para> |
---|
[1211] | 1058 | Options are available in the all Penelope Models, allowing to set |
---|
| 1059 | (and retrieve) the verbosity level of the model, namely the amount of |
---|
| 1060 | information which is printed on the screen. |
---|
[904] | 1061 | |
---|
| 1062 | <itemizedlist spacing="compact"> |
---|
[1211] | 1063 | <listitem><para> |
---|
| 1064 | SetVerbosityLevel(G4int) |
---|
| 1065 | </para></listitem> |
---|
| 1066 | <listitem><para> |
---|
| 1067 | GetVerbosityLevel() |
---|
| 1068 | </para></listitem> |
---|
[904] | 1069 | </itemizedlist> |
---|
| 1070 | </para> |
---|
| 1071 | |
---|
| 1072 | <para> |
---|
[1211] | 1073 | The default verbosity level is 0 (namely, no textual output on the screen). |
---|
| 1074 | The default value should be used in general for normal runs. Higher |
---|
| 1075 | verbosity levels are suggested only for testing and debugging purposes. |
---|
| 1076 | </para> |
---|
[904] | 1077 | |
---|
[1211] | 1078 | <para> |
---|
| 1079 | The verbosity scale defined for all Penelope processes is the following: |
---|
| 1080 | |
---|
[904] | 1081 | <itemizedlist spacing="compact"> |
---|
[1211] | 1082 | <listitem><para> |
---|
| 1083 | 0 = no printout on the screen (default) |
---|
| 1084 | </para></listitem> |
---|
| 1085 | <listitem><para> |
---|
| 1086 | 1 = issue warnings only in the case of energy non-conservation in the final state (should never happen) |
---|
| 1087 | </para></listitem> |
---|
| 1088 | <listitem><para> |
---|
| 1089 | 2 = reports full details on the energy budget in the final state |
---|
| 1090 | </para></listitem> |
---|
| 1091 | <listitem><para> |
---|
| 1092 | 3 = writes also informations on cross section calculation, data file opening and sampling of atoms |
---|
| 1093 | </para></listitem> |
---|
| 1094 | <listitem><para> |
---|
| 1095 | 4 = issues messages when entering in methods |
---|
| 1096 | </para></listitem> |
---|
[904] | 1097 | </itemizedlist> |
---|
| 1098 | </para> |
---|
| 1099 | |
---|
| 1100 | <para> |
---|
[1211] | 1101 | Options are available in G4PenelopeComptonModel, G4PenelopePhotoElectricModel |
---|
| 1102 | and G4PenelopeIonisationModel to enable or disable the usage of atomic |
---|
| 1103 | de-excitation via the G4AtomicDeexcitation module. |
---|
| 1104 | |
---|
| 1105 | <itemizedlist spacing="compact"> |
---|
| 1106 | <listitem><para> |
---|
| 1107 | SetDeexcitationFlag(G4bool) |
---|
| 1108 | </para></listitem> |
---|
| 1109 | <listitem><para> |
---|
| 1110 | DeexcitationFlag() |
---|
| 1111 | </para></listitem> |
---|
| 1112 | </itemizedlist> |
---|
[904] | 1113 | </para> |
---|
| 1114 | |
---|
[1211] | 1115 | <para> |
---|
| 1116 | The default is âtrueâ, namely vacancies in atomic shells produced by the |
---|
| 1117 | interaction are handled by the G4AtomicDeexcitation module, possibly with |
---|
| 1118 | the subsequent emission of fluorescence x-rays. If is set to âfalseâ |
---|
| 1119 | by the user, the energy released in the re-arrangement of atomic vacancies |
---|
| 1120 | is treated in the model as a local energy deposit, without emission of |
---|
| 1121 | secondary particles. The methods are actually inherited from G4VEmModel, |
---|
| 1122 | so they work for all Penelope models; by the way, they have effect only |
---|
| 1123 | in G4PenelopeComptonModel, G4PenelopePhotoElectricModel and |
---|
| 1124 | G4PenelopeIonisationModel. |
---|
| 1125 | </para> |
---|
| 1126 | |
---|
| 1127 | <para> |
---|
| 1128 | An option is also available in these models to enable the production of |
---|
| 1129 | Auger electrons by the G4AtomicDeexcitation module ActivateAuger(G4bool). |
---|
| 1130 | The default (coming from G4AtomicDeexcitation) is âfalseâ, namely only |
---|
| 1131 | fluorescence x-rays are emitted but not Auger electrons. One should |
---|
| 1132 | notice that this option has effect only if the usage of the atomic |
---|
| 1133 | deexcitation is enabled. A warning message is printed if one tries to |
---|
| 1134 | enable the emission of the Auger electrons after having disabled the |
---|
| 1135 | atomic deexcitation via SetDeexcitationFlag(false). |
---|
| 1136 | </para> |
---|
| 1137 | |
---|
| 1138 | </sect4> |
---|
[904] | 1139 | </sect3> |
---|
| 1140 | |
---|
[1211] | 1141 | |
---|
| 1142 | |
---|
[904] | 1143 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 1144 | <sect3 id="sect.PhysProc.EleMag.VeryLowE"> |
---|
| 1145 | <title> |
---|
[921] | 1146 | Very Low energy Electromagnetic Processes (Geant4-DNA extension) |
---|
[904] | 1147 | </title> |
---|
| 1148 | |
---|
| 1149 | <para> |
---|
[1211] | 1150 | The Geant4 low energy electromagnetic Physics package has been extended |
---|
| 1151 | down to energies of a few electronVolts suitable for the simulation of |
---|
| 1152 | radiation effects in liquid water for applications in microdosimetry at |
---|
| 1153 | the cellular and sub-cellular level. These developments take place in |
---|
| 1154 | the framework of the on-going Geant4-DNA project (see the web pages |
---|
| 1155 | of the |
---|
| 1156 | <ulink url="http://geant4.web.cern.ch/geant4/collaboration/working_groups/LEelectromagnetic/">Geant4 Low Energy Electromagnetic Physics Working Group</ulink>). |
---|
[904] | 1157 | </para> |
---|
| 1158 | |
---|
| 1159 | <para> |
---|
[1211] | 1160 | The Geant4-DNA process and model classes apply to electrons, protons, |
---|
| 1161 | hydrogen, alpha particles and their charge states. |
---|
[904] | 1162 | </para> |
---|
| 1163 | |
---|
| 1164 | |
---|
| 1165 | <!-- ******* Bridgehead ******* --> |
---|
| 1166 | <bridgehead renderas='sect4'> |
---|
[1211] | 1167 | Electron processes and models |
---|
[904] | 1168 | </bridgehead> |
---|
| 1169 | <para> |
---|
| 1170 | <itemizedlist spacing="compact"> |
---|
| 1171 | <listitem><para> |
---|
[1211] | 1172 | Elastic scattering : |
---|
[904] | 1173 | <itemizedlist spacing="compact"> |
---|
| 1174 | <listitem><para> |
---|
[1211] | 1175 | process class is G4DNAElastic |
---|
[904] | 1176 | </para></listitem> |
---|
| 1177 | <listitem><para> |
---|
[1211] | 1178 | two alternative model classes are : G4DNAScreenedRutherfordElasticModel |
---|
| 1179 | or G4DNAChampionElasticModel |
---|
[904] | 1180 | </para></listitem> |
---|
| 1181 | </itemizedlist> |
---|
| 1182 | </para></listitem> |
---|
[1211] | 1183 | |
---|
[904] | 1184 | <listitem><para> |
---|
[1211] | 1185 | Excitation |
---|
[904] | 1186 | <itemizedlist spacing="compact"> |
---|
| 1187 | <listitem><para> |
---|
[1211] | 1188 | process class is G4DNAExcitation |
---|
[904] | 1189 | </para></listitem> |
---|
| 1190 | <listitem><para> |
---|
[1211] | 1191 | model class is G4DNAEmfietzoglouExcitationModel |
---|
[904] | 1192 | </para></listitem> |
---|
| 1193 | </itemizedlist> |
---|
| 1194 | </para></listitem> |
---|
[1211] | 1195 | |
---|
[904] | 1196 | <listitem><para> |
---|
[1211] | 1197 | Ionisation |
---|
[904] | 1198 | <itemizedlist spacing="compact"> |
---|
| 1199 | <listitem><para> |
---|
[1211] | 1200 | process class is G4DNAIonisation |
---|
[904] | 1201 | </para></listitem> |
---|
| 1202 | <listitem><para> |
---|
[1211] | 1203 | model class is G4DNABornIonisationModel |
---|
[904] | 1204 | </para></listitem> |
---|
| 1205 | </itemizedlist> |
---|
| 1206 | </para></listitem> |
---|
| 1207 | </itemizedlist> |
---|
| 1208 | </para> |
---|
| 1209 | |
---|
| 1210 | <!-- ******* Bridgehead ******* --> |
---|
| 1211 | <bridgehead renderas='sect4'> |
---|
[1211] | 1212 | Proton processes and models |
---|
[904] | 1213 | </bridgehead> |
---|
| 1214 | <para> |
---|
| 1215 | <itemizedlist spacing="compact"> |
---|
| 1216 | <listitem><para> |
---|
[1211] | 1217 | Excitation |
---|
[904] | 1218 | <itemizedlist spacing="compact"> |
---|
| 1219 | <listitem><para> |
---|
[1211] | 1220 | process class is G4DNAExcitation |
---|
[904] | 1221 | </para></listitem> |
---|
| 1222 | <listitem><para> |
---|
[1211] | 1223 | two complementary model classes are G4DNAMillerGreenExcitationModel |
---|
| 1224 | (below 500 keV) and G4DNABornExcitationModel (above) |
---|
[904] | 1225 | </para></listitem> |
---|
| 1226 | </itemizedlist> |
---|
| 1227 | </para></listitem> |
---|
[1211] | 1228 | |
---|
[904] | 1229 | <listitem><para> |
---|
[1211] | 1230 | Ionisation |
---|
[904] | 1231 | <itemizedlist spacing="compact"> |
---|
| 1232 | <listitem><para> |
---|
[1211] | 1233 | process class is G4DNAIonisation |
---|
[904] | 1234 | </para></listitem> |
---|
| 1235 | <listitem><para> |
---|
[1211] | 1236 | two complementary model classes are G4DNARuddIonisationModel |
---|
| 1237 | (below 500 keV) and G4DNABornIonisationModel (above) |
---|
[904] | 1238 | </para></listitem> |
---|
| 1239 | </itemizedlist> |
---|
| 1240 | </para></listitem> |
---|
[1211] | 1241 | |
---|
[904] | 1242 | <listitem><para> |
---|
[1211] | 1243 | Charge decrease |
---|
[904] | 1244 | <itemizedlist spacing="compact"> |
---|
| 1245 | <listitem><para> |
---|
[1211] | 1246 | process class is G4DNAChargeDecrease |
---|
[904] | 1247 | </para></listitem> |
---|
| 1248 | <listitem><para> |
---|
[1211] | 1249 | model class is G4DNADingfelderChargeDecreaseModel |
---|
[904] | 1250 | </para></listitem> |
---|
| 1251 | </itemizedlist> |
---|
| 1252 | </para></listitem> |
---|
| 1253 | </itemizedlist> |
---|
| 1254 | </para> |
---|
| 1255 | |
---|
| 1256 | <!-- ******* Bridgehead ******* --> |
---|
| 1257 | <bridgehead renderas='sect4'> |
---|
[1211] | 1258 | Hydrogen processes and models |
---|
[904] | 1259 | </bridgehead> |
---|
| 1260 | <para> |
---|
| 1261 | <itemizedlist spacing="compact"> |
---|
| 1262 | <listitem><para> |
---|
[1211] | 1263 | Ionisation |
---|
[904] | 1264 | <itemizedlist spacing="compact"> |
---|
| 1265 | <listitem><para> |
---|
[1211] | 1266 | process class is G4DNAIonisation |
---|
[904] | 1267 | </para></listitem> |
---|
| 1268 | <listitem><para> |
---|
[1211] | 1269 | model class is G4DNARuddIonisationModel |
---|
[904] | 1270 | </para></listitem> |
---|
| 1271 | </itemizedlist> |
---|
| 1272 | </para></listitem> |
---|
[1211] | 1273 | |
---|
[904] | 1274 | <listitem><para> |
---|
[1211] | 1275 | Charge increase |
---|
[904] | 1276 | <itemizedlist spacing="compact"> |
---|
| 1277 | <listitem><para> |
---|
[1211] | 1278 | process class is G4DNAChargeIncrease |
---|
[904] | 1279 | </para></listitem> |
---|
| 1280 | <listitem><para> |
---|
[1211] | 1281 | model class is G4DNADingfelderChargeIncreaseModel |
---|
[904] | 1282 | </para></listitem> |
---|
| 1283 | </itemizedlist> |
---|
| 1284 | </para></listitem> |
---|
| 1285 | </itemizedlist> |
---|
| 1286 | </para> |
---|
| 1287 | |
---|
| 1288 | <!-- ******* Bridgehead ******* --> |
---|
| 1289 | <bridgehead renderas='sect4'> |
---|
[1211] | 1290 | Helium (neutral) processes and models |
---|
[904] | 1291 | </bridgehead> |
---|
| 1292 | <para> |
---|
| 1293 | <itemizedlist spacing="compact"> |
---|
| 1294 | <listitem><para> |
---|
[1211] | 1295 | Excitation |
---|
[904] | 1296 | <itemizedlist spacing="compact"> |
---|
| 1297 | <listitem><para> |
---|
[1211] | 1298 | process class is G4DNAExcitation |
---|
[904] | 1299 | </para></listitem> |
---|
| 1300 | <listitem><para> |
---|
[1211] | 1301 | model class is G4DNAMillerGreenExcitationModel |
---|
[904] | 1302 | </para></listitem> |
---|
| 1303 | </itemizedlist> |
---|
| 1304 | </para></listitem> |
---|
[1211] | 1305 | |
---|
[904] | 1306 | <listitem><para> |
---|
[1211] | 1307 | Ionisation |
---|
[904] | 1308 | <itemizedlist spacing="compact"> |
---|
| 1309 | <listitem><para> |
---|
[1211] | 1310 | process class is G4DNAIonisation |
---|
[904] | 1311 | </para></listitem> |
---|
| 1312 | <listitem><para> |
---|
[1211] | 1313 | model class is G4DNARuddIonisationModel |
---|
[904] | 1314 | </para></listitem> |
---|
| 1315 | </itemizedlist> |
---|
| 1316 | </para></listitem> |
---|
[1211] | 1317 | |
---|
[904] | 1318 | <listitem><para> |
---|
[1211] | 1319 | Charge increase |
---|
[904] | 1320 | <itemizedlist spacing="compact"> |
---|
| 1321 | <listitem><para> |
---|
[1211] | 1322 | process class is G4DNAChargeIncrease |
---|
[904] | 1323 | </para></listitem> |
---|
| 1324 | <listitem><para> |
---|
[1211] | 1325 | model class is G4DNADingfelderChargeIncreaseModel |
---|
[904] | 1326 | </para></listitem> |
---|
| 1327 | </itemizedlist> |
---|
| 1328 | </para></listitem> |
---|
| 1329 | </itemizedlist> |
---|
| 1330 | </para> |
---|
| 1331 | |
---|
| 1332 | <!-- ******* Bridgehead ******* --> |
---|
| 1333 | <bridgehead renderas='sect4'> |
---|
[1211] | 1334 | Helium+ (ionized once) processes and models |
---|
[904] | 1335 | </bridgehead> |
---|
| 1336 | <para> |
---|
| 1337 | <itemizedlist spacing="compact"> |
---|
| 1338 | <listitem><para> |
---|
[1211] | 1339 | Excitation |
---|
[904] | 1340 | <itemizedlist spacing="compact"> |
---|
| 1341 | <listitem><para> |
---|
[1211] | 1342 | process class is G4DNAExcitation |
---|
[904] | 1343 | </para></listitem> |
---|
| 1344 | <listitem><para> |
---|
[1211] | 1345 | model class is G4DNAMillerGreenExcitationModel |
---|
[904] | 1346 | </para></listitem> |
---|
| 1347 | </itemizedlist> |
---|
| 1348 | </para></listitem> |
---|
[1211] | 1349 | |
---|
[904] | 1350 | <listitem><para> |
---|
[1211] | 1351 | Ionisation |
---|
[904] | 1352 | <itemizedlist spacing="compact"> |
---|
| 1353 | <listitem><para> |
---|
[1211] | 1354 | process class is G4DNAIonisation |
---|
[904] | 1355 | </para></listitem> |
---|
| 1356 | <listitem><para> |
---|
[1211] | 1357 | model classes is G4DNARuddIonisationModel |
---|
[904] | 1358 | </para></listitem> |
---|
| 1359 | </itemizedlist> |
---|
| 1360 | </para></listitem> |
---|
[1211] | 1361 | |
---|
[904] | 1362 | <listitem><para> |
---|
[1211] | 1363 | Charge increase |
---|
[904] | 1364 | <itemizedlist spacing="compact"> |
---|
| 1365 | <listitem><para> |
---|
[1211] | 1366 | process class is G4DNAChargeIncrease |
---|
[904] | 1367 | </para></listitem> |
---|
| 1368 | <listitem><para> |
---|
[1211] | 1369 | model classes is G4DNADingfelderChargeIncreaseModel |
---|
[904] | 1370 | </para></listitem> |
---|
| 1371 | </itemizedlist> |
---|
| 1372 | </para></listitem> |
---|
[1211] | 1373 | |
---|
[904] | 1374 | <listitem><para> |
---|
[1211] | 1375 | Charge decrease |
---|
[904] | 1376 | <itemizedlist spacing="compact"> |
---|
| 1377 | <listitem><para> |
---|
[1211] | 1378 | process class is G4DNAChargeDecrease |
---|
[904] | 1379 | </para></listitem> |
---|
| 1380 | <listitem><para> |
---|
[1211] | 1381 | model classes is G4DNADingfelderChargeDecreaseModel |
---|
[904] | 1382 | </para></listitem> |
---|
| 1383 | </itemizedlist> |
---|
| 1384 | </para></listitem> |
---|
| 1385 | </itemizedlist> |
---|
| 1386 | </para> |
---|
| 1387 | |
---|
| 1388 | <!-- ******* Bridgehead ******* --> |
---|
| 1389 | <bridgehead renderas='sect4'> |
---|
[1211] | 1390 | Helium++ (ionised twice) processes and models |
---|
[904] | 1391 | </bridgehead> |
---|
| 1392 | <para> |
---|
| 1393 | <itemizedlist spacing="compact"> |
---|
| 1394 | <listitem><para> |
---|
[1211] | 1395 | Excitation |
---|
[904] | 1396 | <itemizedlist spacing="compact"> |
---|
| 1397 | <listitem><para> |
---|
[1211] | 1398 | process class is G4DNAExcitation |
---|
[904] | 1399 | </para></listitem> |
---|
| 1400 | <listitem><para> |
---|
[1211] | 1401 | model classes is G4DNAMillerGreenExcitationModel |
---|
[904] | 1402 | </para></listitem> |
---|
| 1403 | </itemizedlist> |
---|
| 1404 | </para></listitem> |
---|
[1211] | 1405 | |
---|
[904] | 1406 | <listitem><para> |
---|
[1211] | 1407 | Ionisation |
---|
[904] | 1408 | <itemizedlist spacing="compact"> |
---|
| 1409 | <listitem><para> |
---|
[1211] | 1410 | process class is G4DNAIonisation |
---|
[904] | 1411 | </para></listitem> |
---|
| 1412 | <listitem><para> |
---|
[1211] | 1413 | model classes is G4DNARuddIonisationModel |
---|
[904] | 1414 | </para></listitem> |
---|
| 1415 | </itemizedlist> |
---|
| 1416 | </para></listitem> |
---|
[1211] | 1417 | |
---|
[904] | 1418 | <listitem><para> |
---|
[1211] | 1419 | Charge decrease |
---|
[904] | 1420 | <itemizedlist spacing="compact"> |
---|
| 1421 | <listitem><para> |
---|
[1211] | 1422 | process class is G4DNAChargeDecrease |
---|
[904] | 1423 | </para></listitem> |
---|
| 1424 | <listitem><para> |
---|
[1211] | 1425 | model classes is G4DNADingfelderChargeDecreaseModel |
---|
[904] | 1426 | </para></listitem> |
---|
| 1427 | </itemizedlist> |
---|
| 1428 | </para></listitem> |
---|
| 1429 | </itemizedlist> |
---|
| 1430 | </para> |
---|
| 1431 | |
---|
| 1432 | <para> |
---|
[1211] | 1433 | An example of the registration of these processes in a physics list is |
---|
| 1434 | given here below and may be found in the microdosimetry advanced example. |
---|
[904] | 1435 | |
---|
[1211] | 1436 | |
---|
[904] | 1437 | <informalexample> |
---|
| 1438 | <programlisting> |
---|
[1211] | 1439 | #include "G4DNAElastic.hh" |
---|
| 1440 | #include "G4DNAChampionElasticModel.hh" |
---|
| 1441 | #include "G4DNAScreenedRutherfordElasticModel.hh" |
---|
[904] | 1442 | |
---|
[1211] | 1443 | #include "G4DNAExcitation.hh" |
---|
| 1444 | #include "G4DNAEmfietzoglouExcitationModel.hh" |
---|
| 1445 | #include "G4DNAMillerGreenExcitationModel.hh" |
---|
| 1446 | #include "G4DNABornExcitationModel.hh" |
---|
[904] | 1447 | |
---|
[1211] | 1448 | #include "G4DNAIonisation.hh" |
---|
| 1449 | #include "G4DNABornIonisationModel.hh" |
---|
| 1450 | #include "G4DNARuddIonisationModel.hh" |
---|
[904] | 1451 | |
---|
[1211] | 1452 | #include "G4DNAChargeDecrease.hh" |
---|
| 1453 | #include "G4DNADingfelderChargeDecreaseModel.hh" |
---|
[904] | 1454 | |
---|
[1211] | 1455 | #include "G4DNAChargeIncrease.hh" |
---|
| 1456 | #include "G4DNADingfelderChargeIncreaseModel.hh" |
---|
[904] | 1457 | |
---|
[1211] | 1458 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
---|
[921] | 1459 | |
---|
[1211] | 1460 | void PhysicsList::ConstructEM() |
---|
[904] | 1461 | { |
---|
| 1462 | theParticleIterator->reset(); |
---|
| 1463 | |
---|
[1211] | 1464 | while( (*theParticleIterator)() ) |
---|
| 1465 | { |
---|
[904] | 1466 | |
---|
| 1467 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
[1211] | 1468 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
[904] | 1469 | G4String particleName = particle->GetParticleName(); |
---|
| 1470 | |
---|
[1211] | 1471 | // DNA processes per particle type |
---|
| 1472 | |
---|
[904] | 1473 | if (particleName == "e-") { |
---|
| 1474 | |
---|
[1211] | 1475 | G4DNAElastic* theDNAElasticProcess = new G4DNAElastic("e-_G4DNAElastic"); |
---|
| 1476 | theDNAElasticProcess->SetModel(new G4DNAChampionElasticModel()); |
---|
| 1477 | // or alternative model |
---|
| 1478 | // theDNAElasticProcess->SetModel(new G4DNAScreenedRutherfordElasticModel()); |
---|
| 1479 | pmanager->AddDiscreteProcess(theDNAElasticProcess); |
---|
| 1480 | |
---|
| 1481 | pmanager->AddDiscreteProcess(new G4DNAExcitation("e-_G4DNAExcitation")); |
---|
| 1482 | pmanager->AddDiscreteProcess(new G4DNAIonisation("e-_G4DNAIonisation")); |
---|
| 1483 | |
---|
[904] | 1484 | } else if ( particleName == "proton" ) { |
---|
| 1485 | |
---|
[1211] | 1486 | pmanager->AddDiscreteProcess(new G4DNAExcitation("proton_G4DNAExcitation")); |
---|
| 1487 | pmanager->AddDiscreteProcess(new G4DNAIonisation("proton_G4DNAIonisation")); |
---|
| 1488 | pmanager->AddDiscreteProcess(new G4DNAChargeDecrease("proton_G4DNAChargeDecrease")); |
---|
| 1489 | |
---|
[904] | 1490 | } else if ( particleName == "hydrogen" ) { |
---|
| 1491 | |
---|
[1211] | 1492 | pmanager->AddDiscreteProcess(new G4DNAIonisation("hydrogen_G4DNAIonisation")); |
---|
| 1493 | pmanager->AddDiscreteProcess(new G4DNAChargeIncrease("hydrogen_G4DNAChargeIncrease")); |
---|
| 1494 | |
---|
[904] | 1495 | } else if ( particleName == "alpha" ) { |
---|
[1211] | 1496 | |
---|
| 1497 | pmanager->AddDiscreteProcess(new G4DNAExcitation("alpha_G4DNAExcitation")); |
---|
| 1498 | pmanager->AddDiscreteProcess(new G4DNAIonisation("alpha_G4DNAIonisation")); |
---|
| 1499 | pmanager->AddDiscreteProcess(new G4DNAChargeDecrease("alpha_G4DNAChargeDecrease")); |
---|
| 1500 | |
---|
[904] | 1501 | } else if ( particleName == "alpha+" ) { |
---|
[1211] | 1502 | |
---|
| 1503 | pmanager->AddDiscreteProcess(new G4DNAExcitation("alpha+_G4DNAExcitation")); |
---|
| 1504 | pmanager->AddDiscreteProcess(new G4DNAIonisation("alpha+_G4DNAIonisation")); |
---|
| 1505 | pmanager->AddDiscreteProcess(new G4DNAChargeDecrease("alpha+_G4DNAChargeDecrease")); |
---|
| 1506 | pmanager->AddDiscreteProcess(new G4DNAChargeIncrease("alpha+_G4DNAChargeIncrease")); |
---|
| 1507 | |
---|
[904] | 1508 | } else if ( particleName == "helium" ) { |
---|
[1211] | 1509 | |
---|
| 1510 | pmanager->AddDiscreteProcess(new G4DNAExcitation("helium_G4DNAExcitation")); |
---|
| 1511 | pmanager->AddDiscreteProcess(new G4DNAIonisation("helium_G4DNAIonisation")); |
---|
| 1512 | pmanager->AddDiscreteProcess(new G4DNAChargeIncrease("helium_G4DNAChargeIncrease")); |
---|
| 1513 | |
---|
[904] | 1514 | } |
---|
| 1515 | |
---|
[1211] | 1516 | } // Loop on particles |
---|
[904] | 1517 | } |
---|
| 1518 | |
---|
[1211] | 1519 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
---|
[904] | 1520 | </programlisting> |
---|
| 1521 | </informalexample> |
---|
| 1522 | </para> |
---|
| 1523 | |
---|
| 1524 | <para> |
---|
[1211] | 1525 | Note that in the above example, "alpha" particles are helium atoms ionised |
---|
[904] | 1526 | twice and "helium" particles are neutral helium atoms. The definition of |
---|
| 1527 | particles in the physics list may be for example implemented as follows : |
---|
| 1528 | |
---|
| 1529 | <informalexample> |
---|
| 1530 | <programlisting> |
---|
| 1531 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 1532 | |
---|
| 1533 | #include "G4DNAGenericIonsManager.hh" |
---|
[1211] | 1534 | void PhysicsList::ConstructBaryons() |
---|
[904] | 1535 | { |
---|
[1211] | 1536 | // construct baryons --- |
---|
| 1537 | // Geant4 DNA particles |
---|
| 1538 | G4GenericIon::GenericIonDefinition()Â ; |
---|
| 1539 | G4DNAGenericIonsManager * genericIonsManager; |
---|
| 1540 | genericIonsManager=G4DNAGenericIonsManager::Instance(); |
---|
| 1541 | genericIonsManager->GetIon("alpha++"); |
---|
| 1542 | genericIonsManager->GetIon("alpha+"); |
---|
| 1543 | genericIonsManager->GetIon("helium"); |
---|
| 1544 | genericIonsManager->GetIon("hydrogen"); |
---|
[904] | 1545 | } |
---|
| 1546 | |
---|
| 1547 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 1548 | </programlisting> |
---|
| 1549 | </informalexample> |
---|
| 1550 | </para> |
---|
| 1551 | |
---|
| 1552 | <para> |
---|
[1211] | 1553 | To run the Geant4-DNA extension, data files need to be copied by the |
---|
| 1554 | user to his/her code repository. These files are distributed together |
---|
| 1555 | with the Geant4 release. The user should set the environment variable |
---|
| 1556 | G4LEDATA to the directory where he/she has copied the files. |
---|
[904] | 1557 | </para> |
---|
| 1558 | |
---|
| 1559 | </sect3> |
---|
| 1560 | </sect2> |
---|
| 1561 | |
---|
| 1562 | |
---|
| 1563 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 1564 | <sect2 id="sect.PhysProc.Had"> |
---|
| 1565 | <title> |
---|
| 1566 | Hadronic Interactions |
---|
| 1567 | </title> |
---|
| 1568 | |
---|
| 1569 | <para> |
---|
| 1570 | This section briefly introduces the hadronic physics processes |
---|
| 1571 | installed in Geant4. For details of the implementation of hadronic |
---|
| 1572 | interactions available in Geant4, please refer to the |
---|
| 1573 | <ulink url="http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/PhysicsReferenceManual/html/PhysicsReferenceManual.html"> |
---|
| 1574 | <emphasis role="bold">Physics Reference Manual</emphasis></ulink>. |
---|
| 1575 | </para> |
---|
| 1576 | |
---|
| 1577 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 1578 | <sect3 id="sect.PhysProc.Had.TreatCross"> |
---|
| 1579 | <title> |
---|
| 1580 | Treatment of Cross Sections |
---|
| 1581 | </title> |
---|
| 1582 | |
---|
| 1583 | <!-- ******* Bridgehead ******* --> |
---|
| 1584 | <bridgehead renderas='sect4'> |
---|
| 1585 | Cross section data sets |
---|
| 1586 | </bridgehead> |
---|
| 1587 | |
---|
| 1588 | <para> |
---|
| 1589 | Each hadronic process object (derived from |
---|
| 1590 | <emphasis>G4HadronicProcess</emphasis>) may have one or more cross section data |
---|
| 1591 | sets associated with it. The term "data set" is meant, in a broad |
---|
| 1592 | sense, to be an object that encapsulates methods and data for |
---|
| 1593 | calculating total cross sections for a given process. The methods |
---|
| 1594 | and data may take many forms, from a simple equation using a few |
---|
| 1595 | hard-wired numbers to a sophisticated parameterisation using large |
---|
| 1596 | data tables. Cross section data sets are derived from the abstract |
---|
| 1597 | class <emphasis>G4VCrossSectionDataSet</emphasis>, and are required to implement |
---|
| 1598 | the following methods: |
---|
| 1599 | |
---|
| 1600 | <informalexample> |
---|
| 1601 | <programlisting> |
---|
| 1602 | G4bool IsApplicable( const G4DynamicParticle*, const G4Element* ) |
---|
| 1603 | </programlisting> |
---|
| 1604 | </informalexample> |
---|
| 1605 | </para> |
---|
| 1606 | |
---|
| 1607 | <para> |
---|
| 1608 | This method must return <literal>True</literal> if the data set is able to |
---|
| 1609 | calculate a total cross section for the given particle and |
---|
| 1610 | material, and <literal>False</literal> otherwise. |
---|
| 1611 | |
---|
| 1612 | <informalexample> |
---|
| 1613 | <programlisting> |
---|
| 1614 | G4double GetCrossSection( const G4DynamicParticle*, const G4Element* ) |
---|
| 1615 | </programlisting> |
---|
| 1616 | </informalexample> |
---|
| 1617 | </para> |
---|
| 1618 | |
---|
| 1619 | <para> |
---|
| 1620 | This method, which will be invoked only if <literal>True</literal> was |
---|
| 1621 | returned by <literal>IsApplicable</literal>, must return a cross section, in |
---|
| 1622 | Geant4 default units, for the given particle and material. |
---|
| 1623 | |
---|
| 1624 | <informalexample> |
---|
| 1625 | <programlisting> |
---|
| 1626 | void BuildPhysicsTable( const G4ParticleDefinition& ) |
---|
| 1627 | </programlisting> |
---|
| 1628 | </informalexample> |
---|
| 1629 | </para> |
---|
| 1630 | |
---|
| 1631 | <para> |
---|
| 1632 | This method may be invoked to request the data set to recalculate |
---|
| 1633 | its internal database or otherwise reset its state after a change |
---|
| 1634 | in the cuts or other parameters of the given particle type. |
---|
| 1635 | |
---|
| 1636 | |
---|
| 1637 | <informalexample> |
---|
| 1638 | <programlisting> |
---|
| 1639 | void DumpPhysicsTable( const G4ParticleDefinition& ) = 0 |
---|
| 1640 | </programlisting> |
---|
| 1641 | </informalexample> |
---|
| 1642 | </para> |
---|
| 1643 | |
---|
| 1644 | <para> |
---|
| 1645 | This method may be invoked to request the data set to print its |
---|
| 1646 | internal database and/or other state information, for the given |
---|
| 1647 | particle type, to the standard output stream. |
---|
| 1648 | </para> |
---|
| 1649 | |
---|
| 1650 | <!-- ******* Bridgehead ******* --> |
---|
| 1651 | <bridgehead renderas='sect4'> |
---|
| 1652 | Cross section data store |
---|
| 1653 | </bridgehead> |
---|
| 1654 | |
---|
| 1655 | <para> |
---|
| 1656 | Cross section data sets are used by the process for the |
---|
| 1657 | calculation of the physical interaction length. A given cross |
---|
| 1658 | section data set may only apply to a certain energy range, or may |
---|
| 1659 | only be able to calculate cross sections for a particular type of |
---|
| 1660 | particle. The class <emphasis>G4CrossSectionDataStore</emphasis> has been |
---|
| 1661 | provided to allow the user to specify, if desired, a series of data |
---|
| 1662 | sets for a process, and to arrange the priority of data sets so |
---|
| 1663 | that the appropriate one is used for a given energy range, |
---|
| 1664 | particle, and material. It implements the following public |
---|
| 1665 | methods: |
---|
| 1666 | |
---|
| 1667 | <informalexample> |
---|
| 1668 | <programlisting> |
---|
| 1669 | G4CrossSectionDataStore() |
---|
| 1670 | |
---|
| 1671 | ~G4CrossSectionDataStore() |
---|
| 1672 | </programlisting> |
---|
| 1673 | </informalexample> |
---|
| 1674 | |
---|
| 1675 | and |
---|
| 1676 | |
---|
| 1677 | <informalexample> |
---|
| 1678 | <programlisting> |
---|
| 1679 | G4double GetCrossSection( const G4DynamicParticle*, const G4Element* ) |
---|
| 1680 | </programlisting> |
---|
| 1681 | </informalexample> |
---|
| 1682 | </para> |
---|
| 1683 | |
---|
| 1684 | <para> |
---|
| 1685 | For a given particle and material, this method returns a cross |
---|
| 1686 | section value provided by one of the collection of cross section |
---|
| 1687 | data sets listed in the data store object. If there are no known |
---|
| 1688 | data sets, a <literal>G4Exception</literal> is thrown and <literal>DBL_MIN</literal> is |
---|
| 1689 | returned. Otherwise, each data set in the list is queried, in |
---|
| 1690 | reverse list order, by invoking its <literal>IsApplicable</literal> method |
---|
| 1691 | for the given particle and material. The first data set object that |
---|
| 1692 | responds positively will then be asked to return a cross section |
---|
| 1693 | value via its <literal>GetCrossSection</literal> method. If no data set |
---|
| 1694 | responds positively, a <literal>G4Exception</literal> is thrown and |
---|
| 1695 | <literal>DBL_MIN</literal> is returned. |
---|
| 1696 | </para> |
---|
| 1697 | |
---|
| 1698 | <para> |
---|
| 1699 | <informalexample> |
---|
| 1700 | <programlisting> |
---|
| 1701 | void AddDataSet( G4VCrossSectionDataSet* aDataSet ) |
---|
| 1702 | </programlisting> |
---|
| 1703 | </informalexample> |
---|
| 1704 | |
---|
| 1705 | This method adds the given cross section data set to the end of the |
---|
| 1706 | list of data sets in the data store. For the evaluation of cross |
---|
| 1707 | sections, the list has a LIFO (Last In First Out) priority, meaning |
---|
| 1708 | that data sets added later to the list will have priority over |
---|
| 1709 | those added earlier to the list. Another way of saying this, is |
---|
| 1710 | that the data store, when given a <literal>GetCrossSection</literal> request, |
---|
| 1711 | does the <literal>IsApplicable</literal> queries in the reverse list order, |
---|
| 1712 | starting with the last data set in the list and proceeding to the |
---|
| 1713 | first, and the first data set that responds positively is used to |
---|
| 1714 | calculate the cross section. |
---|
| 1715 | </para> |
---|
| 1716 | |
---|
| 1717 | <para> |
---|
| 1718 | <informalexample> |
---|
| 1719 | <programlisting> |
---|
| 1720 | void BuildPhysicsTable( const G4ParticleDefinition& aParticleType ) |
---|
| 1721 | </programlisting> |
---|
| 1722 | </informalexample> |
---|
| 1723 | |
---|
| 1724 | This method may be invoked to indicate to the data store that there |
---|
| 1725 | has been a change in the cuts or other parameters of the given |
---|
| 1726 | particle type. In response, the data store will invoke the |
---|
| 1727 | <literal>BuildPhysicsTable</literal> of each of its data sets. |
---|
| 1728 | </para> |
---|
| 1729 | |
---|
| 1730 | <para> |
---|
| 1731 | <informalexample> |
---|
| 1732 | <programlisting> |
---|
| 1733 | void DumpPhysicsTable( const G4ParticleDefinition& ) |
---|
| 1734 | </programlisting> |
---|
| 1735 | </informalexample> |
---|
| 1736 | |
---|
| 1737 | This method may be used to request the data store to invoke the |
---|
| 1738 | <literal>DumpPhysicsTable</literal> method of each of its data sets. |
---|
| 1739 | </para> |
---|
| 1740 | |
---|
| 1741 | <!-- ******* Bridgehead ******* --> |
---|
| 1742 | <bridgehead renderas='sect4'> |
---|
| 1743 | Default cross sections |
---|
| 1744 | </bridgehead> |
---|
| 1745 | |
---|
| 1746 | <para> |
---|
| 1747 | The defaults for total cross section data and calculations have |
---|
| 1748 | been encapsulated in the singleton class |
---|
| 1749 | <emphasis>G4HadronCrossSections</emphasis>. Each hadronic process: |
---|
| 1750 | <emphasis>G4HadronInelasticProcess</emphasis>, |
---|
| 1751 | <emphasis>G4HadronElasticProcess</emphasis>, |
---|
| 1752 | <emphasis>G4HadronFissionProcess</emphasis>, |
---|
| 1753 | and <emphasis>G4HadronCaptureProcess</emphasis>, |
---|
| 1754 | comes already equipped with a cross section data store and a |
---|
| 1755 | default cross section data set. The data set objects are really |
---|
| 1756 | just shells that invoke the singleton <emphasis>G4HadronCrossSections</emphasis> |
---|
| 1757 | to do the real work of calculating cross sections. |
---|
| 1758 | </para> |
---|
| 1759 | |
---|
| 1760 | <para> |
---|
| 1761 | The default cross sections can be overridden in whole or in part |
---|
| 1762 | by the user. To this end, the base class <emphasis>G4HadronicProcess</emphasis> |
---|
| 1763 | has a ``get'' method: |
---|
| 1764 | |
---|
| 1765 | <informalexample> |
---|
| 1766 | <programlisting> |
---|
| 1767 | G4CrossSectionDataStore* GetCrossSectionDataStore() |
---|
| 1768 | </programlisting> |
---|
| 1769 | </informalexample> |
---|
| 1770 | |
---|
| 1771 | which gives public access to the data store for each process. The |
---|
| 1772 | user's cross section data sets can be added to the data store |
---|
| 1773 | according to the following framework: |
---|
| 1774 | |
---|
| 1775 | <informalexample> |
---|
| 1776 | <programlisting> |
---|
| 1777 | G4Hadron...Process aProcess(...) |
---|
| 1778 | |
---|
| 1779 | MyCrossSectionDataSet myDataSet(...) |
---|
| 1780 | |
---|
| 1781 | aProcess.GetCrossSectionDataStore()->AddDataSet( &MyDataSet ) |
---|
| 1782 | </programlisting> |
---|
| 1783 | </informalexample> |
---|
| 1784 | </para> |
---|
| 1785 | |
---|
| 1786 | <para> |
---|
| 1787 | The added data set will override the default cross section data |
---|
| 1788 | whenever so indicated by its <literal>IsApplicable</literal> method. |
---|
| 1789 | </para> |
---|
| 1790 | |
---|
| 1791 | <para> |
---|
| 1792 | In addition to the ``get'' method, <emphasis>G4HadronicProcess</emphasis> also |
---|
| 1793 | has the method |
---|
| 1794 | |
---|
| 1795 | <informalexample> |
---|
| 1796 | <programlisting> |
---|
| 1797 | void SetCrossSectionDataStore( G4CrossSectionDataStore* ) |
---|
| 1798 | </programlisting> |
---|
| 1799 | </informalexample> |
---|
| 1800 | |
---|
| 1801 | which allows the user to completely replace the default data |
---|
| 1802 | store with a new data store. |
---|
| 1803 | </para> |
---|
| 1804 | |
---|
| 1805 | <para> |
---|
| 1806 | It should be noted that a process does not send any information |
---|
| 1807 | about itself to its associated data store (and hence data set) |
---|
| 1808 | objects. Thus, each data set is assumed to be formulated to |
---|
| 1809 | calculate cross sections for one and only one type of process. Of |
---|
| 1810 | course, this does not prevent different data sets from sharing |
---|
| 1811 | common data and/or calculation methods, as in the case of the |
---|
| 1812 | <emphasis>G4HadronCrossSections</emphasis> class mentioned above. Indeed, |
---|
| 1813 | <emphasis>G4VCrossSectionDataSet</emphasis> specifies only the abstract interface |
---|
| 1814 | between physics processes and their data sets, and leaves the user |
---|
| 1815 | free to implement whatever sort of underlying structure is |
---|
| 1816 | appropriate. |
---|
| 1817 | </para> |
---|
| 1818 | |
---|
| 1819 | <para> |
---|
| 1820 | The current implementation of the data set |
---|
| 1821 | <emphasis>G4HadronCrossSections</emphasis> reuses the total cross-sections for |
---|
| 1822 | inelastic and elastic scattering, radiative capture and fission as |
---|
| 1823 | used with <emphasis role="bold">GHEISHA</emphasis> to provide cross-sections |
---|
| 1824 | for calculation |
---|
| 1825 | of the respective mean free paths of a given particle in a given |
---|
| 1826 | material. |
---|
| 1827 | </para> |
---|
| 1828 | |
---|
| 1829 | <!-- ******* Bridgehead ******* --> |
---|
| 1830 | <bridgehead renderas='sect4'> |
---|
| 1831 | Cross-sections for low energy neutron transport |
---|
| 1832 | </bridgehead> |
---|
| 1833 | |
---|
| 1834 | <para> |
---|
| 1835 | The cross section data for low energy neutron transport are |
---|
| 1836 | organized in a set of files that are read in by the corresponding |
---|
| 1837 | data set classes at time zero. Hereby the file system is used, in |
---|
| 1838 | order to allow highly granular access to the data. The ``root'' |
---|
| 1839 | directory of the cross-section directory structure is accessed |
---|
| 1840 | through an environment variable, <literal>NeutronHPCrossSections</literal>, |
---|
| 1841 | which is to be set by the user. The classes accessing the total |
---|
| 1842 | cross-sections of the individual processes, i.e., the cross-section |
---|
| 1843 | data set classes for low energy neutron transport, are |
---|
| 1844 | <emphasis>G4NeutronHPElasticData</emphasis>, |
---|
| 1845 | <emphasis>G4NeutronHPCaptureData</emphasis>, |
---|
| 1846 | <emphasis>G4NeutronHPFissionData</emphasis>, |
---|
| 1847 | and <emphasis>G4NeutronHPInelasticData</emphasis>. |
---|
| 1848 | </para> |
---|
| 1849 | |
---|
| 1850 | <para> |
---|
| 1851 | For detailed descriptions of the low energy neutron total |
---|
| 1852 | cross-sections, they may be registered by the user as described |
---|
| 1853 | above with the data stores of the corresponding processes for |
---|
| 1854 | neutron interactions. |
---|
| 1855 | </para> |
---|
| 1856 | |
---|
| 1857 | <para> |
---|
| 1858 | It should be noted that using these total cross section classes |
---|
| 1859 | does not require that the neutron_hp models also be used. It is up |
---|
| 1860 | to the user to decide whethee this is desirable or not for his |
---|
| 1861 | particular problem. |
---|
| 1862 | </para> |
---|
| 1863 | |
---|
| 1864 | </sect3> |
---|
| 1865 | |
---|
| 1866 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 1867 | <sect3 id="sect.PhysProc.Had.AtRest"> |
---|
| 1868 | <title> |
---|
| 1869 | Hadrons at Rest |
---|
| 1870 | </title> |
---|
| 1871 | |
---|
| 1872 | <!-- ******* Bridgehead ******* --> |
---|
| 1873 | <bridgehead renderas='sect4'> |
---|
| 1874 | List of implemented "Hadron at Rest" processes |
---|
| 1875 | </bridgehead> |
---|
| 1876 | |
---|
| 1877 | <para> |
---|
| 1878 | The following process classes have been implemented: |
---|
| 1879 | |
---|
| 1880 | <itemizedlist spacing="compact"> |
---|
| 1881 | <listitem><para> |
---|
| 1882 | pi- absorption (class name <emphasis>G4PionMinusAbsorptionAtRest</emphasis> |
---|
| 1883 | or <emphasis>G4PiMinusAbsorptionAtRest</emphasis>) |
---|
| 1884 | </para></listitem> |
---|
| 1885 | <listitem><para> |
---|
| 1886 | kaon- absorption (class name <emphasis>G4KaonMinusAbsorptionAtRest</emphasis> |
---|
| 1887 | or <emphasis>G4KaonMinusAbsorption</emphasis>) |
---|
| 1888 | </para></listitem> |
---|
| 1889 | <listitem><para> |
---|
| 1890 | neutron capture (class name <emphasis>G4NeutronCaptureAtRest</emphasis>) |
---|
| 1891 | </para></listitem> |
---|
| 1892 | <listitem><para> |
---|
| 1893 | anti-proton annihilation (class name |
---|
| 1894 | <emphasis>G4AntiProtonAnnihilationAtRest</emphasis>) |
---|
| 1895 | </para></listitem> |
---|
| 1896 | <listitem><para> |
---|
| 1897 | anti-neutron annihilation (class name |
---|
| 1898 | <emphasis>G4AntiNeutronAnnihilationAtRest</emphasis>) |
---|
| 1899 | </para></listitem> |
---|
| 1900 | <listitem><para> |
---|
| 1901 | mu- capture (class name <emphasis>G4MuonMinusCaptureAtRest</emphasis>) |
---|
| 1902 | </para></listitem> |
---|
| 1903 | <listitem><para> |
---|
| 1904 | alternative CHIPS model for any negativly charged particle |
---|
| 1905 | (class name <emphasis>G4QCaptureAtRest</emphasis>) |
---|
| 1906 | </para></listitem> |
---|
| 1907 | </itemizedlist> |
---|
| 1908 | </para> |
---|
| 1909 | |
---|
| 1910 | <para> |
---|
| 1911 | Obviously the last process does not, strictly speaking, deal with a |
---|
| 1912 | ``hadron at rest''. It does, nonetheless, share common features |
---|
| 1913 | with the others in the above list because of the implementation |
---|
| 1914 | model chosen. The differences between the alternative |
---|
| 1915 | implementation for kaon and pion absorption concern the fast part |
---|
| 1916 | of the emitted particle spectrum. G4PiMinusAbsorptionAtRest, and |
---|
| 1917 | G4KaonMinusAbsorptionAtRest focus especially on a good description |
---|
| 1918 | of this part of the spectrum. |
---|
| 1919 | </para> |
---|
| 1920 | |
---|
| 1921 | <!-- ******* Bridgehead ******* --> |
---|
| 1922 | <bridgehead renderas='sect4'> |
---|
| 1923 | Implementation Interface to Geant4 |
---|
| 1924 | </bridgehead> |
---|
| 1925 | |
---|
| 1926 | <para> |
---|
| 1927 | All of these classes are derived from the abstract class |
---|
| 1928 | <emphasis>G4VRestProcess</emphasis>. In addition to the constructor and |
---|
| 1929 | destructor methods, the following public methods of the abstract |
---|
| 1930 | class have been implemented for each of the above six |
---|
| 1931 | processes: |
---|
| 1932 | |
---|
| 1933 | <itemizedlist spacing="compact"> |
---|
| 1934 | <listitem><para> |
---|
| 1935 | <para> |
---|
| 1936 | <literal>AtRestGetPhysicalInteractionLength( const G4Track&, |
---|
| 1937 | G4ForceCondition* )</literal> |
---|
| 1938 | </para> |
---|
| 1939 | <para> |
---|
| 1940 | This method returns the time taken before the interaction actually |
---|
| 1941 | occurs. In all processes listed above, except for muon capture, a |
---|
| 1942 | value of zero is returned. For the muon capture process the muon |
---|
| 1943 | capture lifetime is returned. |
---|
| 1944 | </para> |
---|
| 1945 | </para></listitem> |
---|
| 1946 | <listitem><para> |
---|
| 1947 | <para> |
---|
| 1948 | <literal>AtRestDoIt( const G4Track&, const G4Step&)</literal> |
---|
| 1949 | </para> |
---|
| 1950 | <para> |
---|
| 1951 | This method generates the secondary particles produced by the |
---|
| 1952 | process. |
---|
| 1953 | </para> |
---|
| 1954 | </para></listitem> |
---|
| 1955 | <listitem><para> |
---|
| 1956 | <para> |
---|
| 1957 | <literal>IsApplicable( const G4ParticleDefinition& )</literal> |
---|
| 1958 | </para> |
---|
| 1959 | <para> |
---|
| 1960 | This method returns the result of a check to see if the process is |
---|
| 1961 | possible for a given particle. |
---|
| 1962 | </para> |
---|
| 1963 | </para></listitem> |
---|
| 1964 | </itemizedlist> |
---|
| 1965 | </para> |
---|
| 1966 | |
---|
| 1967 | |
---|
| 1968 | <!-- ******* Bridgehead ******* --> |
---|
| 1969 | <bridgehead renderas='sect4'> |
---|
| 1970 | Example of how to use a hadron at rest process |
---|
| 1971 | </bridgehead> |
---|
| 1972 | |
---|
| 1973 | <para> |
---|
| 1974 | Including a ``hadron at rest'' process for a particle, a pi- for |
---|
| 1975 | example, into the Geant4 system is straightforward and can be done |
---|
| 1976 | in the following way: |
---|
| 1977 | |
---|
| 1978 | <itemizedlist spacing="compact"> |
---|
| 1979 | <listitem><para> |
---|
| 1980 | create a process: |
---|
| 1981 | <informalexample> |
---|
| 1982 | <programlisting> |
---|
| 1983 | theProcess = new G4PionMinusAbsorptionAtRest(); |
---|
| 1984 | </programlisting> |
---|
| 1985 | </informalexample> |
---|
| 1986 | </para></listitem> |
---|
| 1987 | <listitem><para> |
---|
| 1988 | register the process with the particle's process manager: |
---|
| 1989 | <informalexample> |
---|
| 1990 | <programlisting> |
---|
| 1991 | theParticleDef = G4PionMinus::PionMinus(); |
---|
| 1992 | G4ProcessManager* pman = theParticleDef->GetProcessManager(); |
---|
| 1993 | pman->AddRestProcess( theProcess ); |
---|
| 1994 | </programlisting> |
---|
| 1995 | </informalexample> |
---|
| 1996 | </para></listitem> |
---|
| 1997 | </itemizedlist> |
---|
| 1998 | </para> |
---|
| 1999 | |
---|
| 2000 | </sect3> |
---|
| 2001 | |
---|
| 2002 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 2003 | <sect3 id="sect.PhysProc.Had.Flight"> |
---|
| 2004 | <title> |
---|
| 2005 | Hadrons in Flight |
---|
| 2006 | </title> |
---|
| 2007 | |
---|
| 2008 | <!-- ******* Bridgehead ******* --> |
---|
| 2009 | <bridgehead renderas='sect4'> |
---|
| 2010 | What processes do you need? |
---|
| 2011 | </bridgehead> |
---|
| 2012 | |
---|
| 2013 | <para> |
---|
| 2014 | For hadrons in motion, there are four physics process classes. |
---|
| 2015 | <xref linkend="table.PhysProc_1" /> shows each process and the |
---|
| 2016 | particles for which it is relevant. |
---|
| 2017 | |
---|
| 2018 | <table id="table.PhysProc_1"> |
---|
| 2019 | <title> |
---|
| 2020 | Hadronic processes and relevant particles. |
---|
| 2021 | </title> |
---|
| 2022 | |
---|
| 2023 | <tgroup cols="2"> |
---|
| 2024 | <tbody> |
---|
| 2025 | <row> |
---|
| 2026 | <entry> |
---|
| 2027 | <emphasis>G4HadronElasticProcess</emphasis> |
---|
| 2028 | </entry> |
---|
| 2029 | <entry> |
---|
| 2030 | pi+, pi-, K<superscript>+</superscript>, |
---|
| 2031 | K<superscript>0</superscript><subscript>S</subscript>, |
---|
| 2032 | K<superscript>0</superscript><subscript>L</subscript>, |
---|
| 2033 | K<superscript>-</superscript>, |
---|
| 2034 | p, p-bar, n, n-bar, lambda, lambda-bar, |
---|
| 2035 | Sigma<superscript>+</superscript>, Sigma<superscript>-</superscript>, |
---|
| 2036 | Sigma<superscript>+</superscript>-bar, |
---|
| 2037 | Sigma<superscript>-</superscript>-bar, |
---|
| 2038 | Xi<superscript>0</superscript>, Xi<superscript>-</superscript>, |
---|
| 2039 | Xi<superscript>0</superscript>-bar, Xi<superscript>-</superscript>-bar |
---|
| 2040 | </entry> |
---|
| 2041 | </row> |
---|
| 2042 | <row> |
---|
| 2043 | <entry> |
---|
| 2044 | <emphasis>G4HadronInelasticProcess</emphasis> |
---|
| 2045 | </entry> |
---|
| 2046 | <entry> |
---|
| 2047 | pi+, pi-, K<superscript>+</superscript>, |
---|
| 2048 | K<superscript>0</superscript><subscript>S</subscript>, |
---|
| 2049 | K<superscript>0</superscript><subscript>L</subscript>, |
---|
| 2050 | K<superscript>-</superscript>, |
---|
| 2051 | p, p-bar, n, n-bar, lambda, lambda-bar, |
---|
| 2052 | Sigma<superscript>+</superscript>, Sigma<superscript>-</superscript>, |
---|
| 2053 | Sigma<superscript>+</superscript>-bar, |
---|
| 2054 | Sigma<superscript>-</superscript>-bar, Xi<superscript>0</superscript>, |
---|
| 2055 | Xi<superscript>-</superscript>, Xi<superscript>0</superscript>-bar, |
---|
| 2056 | Xi<superscript>-</superscript>-bar |
---|
| 2057 | </entry> |
---|
| 2058 | </row> |
---|
| 2059 | <row> |
---|
| 2060 | <entry> |
---|
| 2061 | <emphasis>G4HadronFissionProcess</emphasis> |
---|
| 2062 | </entry> |
---|
| 2063 | <entry> |
---|
| 2064 | all |
---|
| 2065 | </entry> |
---|
| 2066 | </row> |
---|
| 2067 | <row> |
---|
| 2068 | <entry> |
---|
| 2069 | <emphasis>G4CaptureProcess</emphasis> |
---|
| 2070 | </entry> |
---|
| 2071 | <entry> |
---|
| 2072 | n, n-bar |
---|
| 2073 | </entry> |
---|
| 2074 | </row> |
---|
| 2075 | </tbody> |
---|
| 2076 | </tgroup> |
---|
| 2077 | </table> |
---|
| 2078 | </para> |
---|
| 2079 | |
---|
| 2080 | <!-- ******* Bridgehead ******* --> |
---|
| 2081 | <bridgehead renderas='sect4'> |
---|
| 2082 | How to register Models |
---|
| 2083 | </bridgehead> |
---|
| 2084 | |
---|
| 2085 | <para> |
---|
| 2086 | To register an inelastic process model for a particle, a proton |
---|
| 2087 | for example, first get the pointer to the particle's process |
---|
| 2088 | manager: |
---|
| 2089 | |
---|
| 2090 | <informalexample> |
---|
| 2091 | <programlisting> |
---|
| 2092 | G4ParticleDefinition *theProton = G4Proton::ProtonDefinition(); |
---|
| 2093 | G4ProcessManager *theProtonProcMan = theProton->GetProcessManager(); |
---|
| 2094 | </programlisting> |
---|
| 2095 | </informalexample> |
---|
| 2096 | </para> |
---|
| 2097 | |
---|
| 2098 | <para> |
---|
| 2099 | Create an instance of the particle's inelastic process: |
---|
| 2100 | |
---|
| 2101 | <informalexample> |
---|
| 2102 | <programlisting> |
---|
| 2103 | G4ProtonInelasticProcess *theProtonIEProc = new G4ProtonInelasticProcess(); |
---|
| 2104 | </programlisting> |
---|
| 2105 | </informalexample> |
---|
| 2106 | </para> |
---|
| 2107 | |
---|
| 2108 | <para> |
---|
| 2109 | Create an instance of the model which determines the secondaries |
---|
| 2110 | produced in the interaction, and calculates the momenta of the |
---|
| 2111 | particles: |
---|
| 2112 | |
---|
| 2113 | <informalexample> |
---|
| 2114 | <programlisting> |
---|
| 2115 | G4LEProtonInelastic *theProtonIE = new G4LEProtonInelastic(); |
---|
| 2116 | </programlisting> |
---|
| 2117 | </informalexample> |
---|
| 2118 | </para> |
---|
| 2119 | |
---|
| 2120 | <para> |
---|
| 2121 | Register the model with the particle's inelastic process: |
---|
| 2122 | |
---|
| 2123 | <informalexample> |
---|
| 2124 | <programlisting> |
---|
| 2125 | theProtonIEProc->RegisterMe( theProtonIE ); |
---|
| 2126 | </programlisting> |
---|
| 2127 | </informalexample> |
---|
| 2128 | </para> |
---|
| 2129 | |
---|
| 2130 | <para> |
---|
| 2131 | Finally, add the particle's inelastic process to the list of |
---|
| 2132 | discrete processes: |
---|
| 2133 | |
---|
| 2134 | <informalexample> |
---|
| 2135 | <programlisting> |
---|
| 2136 | theProtonProcMan->AddDiscreteProcess( theProtonIEProc ); |
---|
| 2137 | </programlisting> |
---|
| 2138 | </informalexample> |
---|
| 2139 | </para> |
---|
| 2140 | |
---|
| 2141 | <para> |
---|
| 2142 | The particle's inelastic process class, |
---|
| 2143 | <emphasis>G4ProtonInelasticProcess</emphasis> in the example above, derives from |
---|
| 2144 | the <emphasis>G4HadronicInelasticProcess</emphasis> class, and simply defines the |
---|
| 2145 | process name and calls the <emphasis>G4HadronicInelasticProcess</emphasis> |
---|
| 2146 | constructor. All of the specific particle inelastic processes |
---|
| 2147 | derive from the <emphasis>G4HadronicInelasticProcess</emphasis> class, which |
---|
| 2148 | calls the <literal>PostStepDoIt</literal> function, which returns the |
---|
| 2149 | particle change object from the <emphasis>G4HadronicProcess</emphasis> function |
---|
| 2150 | <literal>GeneralPostStepDoIt</literal>. This class also gets the mean free |
---|
| 2151 | path, builds the physics table, and gets the microscopic cross |
---|
| 2152 | section. The <emphasis>G4HadronicInelasticProcess</emphasis> class derives from |
---|
| 2153 | the <emphasis>G4HadronicProcess</emphasis> class, which is the top level hadronic |
---|
| 2154 | process class. The <emphasis>G4HadronicProcess</emphasis> class derives from the |
---|
| 2155 | <emphasis>G4VDiscreteProcess</emphasis> class. The inelastic, elastic, capture, |
---|
| 2156 | and fission processes derive from the <emphasis>G4HadronicProcess</emphasis> |
---|
| 2157 | class. This pure virtual class also provides the energy range |
---|
| 2158 | manager object and the <literal>RegisterMe</literal> access function. |
---|
| 2159 | </para> |
---|
| 2160 | |
---|
| 2161 | <para> |
---|
| 2162 | A sample case for the proton's inelastic interaction model class |
---|
| 2163 | is shown in <xref linkend="programlist_PhysProc_3" />, where |
---|
| 2164 | <literal>G4LEProtonInelastic.hh</literal> is the name of the include |
---|
| 2165 | file: |
---|
| 2166 | |
---|
| 2167 | <example id="programlist_PhysProc_3"> |
---|
| 2168 | <title> |
---|
| 2169 | An example of a proton inelastic interaction model class. |
---|
| 2170 | </title> |
---|
| 2171 | |
---|
| 2172 | <programlisting> |
---|
| 2173 | ----------------------------- include file ------------------------------------------ |
---|
| 2174 | |
---|
| 2175 | #include "G4InelasticInteraction.hh" |
---|
| 2176 | class G4LEProtonInelastic : public G4InelasticInteraction |
---|
| 2177 | { |
---|
| 2178 | public: |
---|
| 2179 | G4LEProtonInelastic() : G4InelasticInteraction() |
---|
| 2180 | { |
---|
| 2181 | SetMinEnergy( 0.0 ); |
---|
| 2182 | SetMaxEnergy( 25.*GeV ); |
---|
| 2183 | } |
---|
| 2184 | ~G4LEProtonInelastic() { } |
---|
| 2185 | G4ParticleChange *ApplyYourself( const G4Track &aTrack, |
---|
| 2186 | G4Nucleus &targetNucleus ); |
---|
| 2187 | private: |
---|
| 2188 | void CascadeAndCalculateMomenta( required arguments ); |
---|
| 2189 | }; |
---|
| 2190 | |
---|
| 2191 | ----------------------------- source file ------------------------------------------ |
---|
| 2192 | |
---|
| 2193 | #include "G4LEProtonInelastic.hh" |
---|
| 2194 | G4ParticleChange * |
---|
| 2195 | G4LEProton Inelastic::ApplyYourself( const G4Track &aTrack, |
---|
| 2196 | G4Nucleus &targetNucleus ) |
---|
| 2197 | { |
---|
| 2198 | theParticleChange.Initialize( aTrack ); |
---|
| 2199 | const G4DynamicParticle *incidentParticle = aTrack.GetDynamicParticle(); |
---|
| 2200 | // create the target particle |
---|
| 2201 | G4DynamicParticle *targetParticle = targetNucleus.ReturnTargetParticle(); |
---|
| 2202 | CascadeAndCalculateMomenta( required arguments ) |
---|
| 2203 | { ... } |
---|
| 2204 | return &theParticleChange; |
---|
| 2205 | } |
---|
| 2206 | </programlisting> |
---|
| 2207 | </example> |
---|
| 2208 | </para> |
---|
| 2209 | |
---|
| 2210 | <para> |
---|
| 2211 | The <literal>CascadeAndCalculateMomenta</literal> function is the bulk of |
---|
| 2212 | the model and is to be provided by the model's creator. It should |
---|
| 2213 | determine what secondary particles are produced in the interaction, |
---|
| 2214 | calculate the momenta for all the particles, and put this |
---|
| 2215 | information into the <emphasis>ParticleChange</emphasis> object which is |
---|
| 2216 | returned. |
---|
| 2217 | </para> |
---|
| 2218 | |
---|
| 2219 | <para> |
---|
| 2220 | The <emphasis>G4LEProtonInelastic</emphasis> class derives from the |
---|
| 2221 | <emphasis>G4InelasticInteraction</emphasis> class, which is an abstract base |
---|
| 2222 | class since the pure virtual function <literal>ApplyYourself</literal> is not |
---|
| 2223 | defined there. <emphasis>G4InelasticInteraction</emphasis> itself derives from |
---|
| 2224 | the <emphasis>G4HadronicInteraction</emphasis> abstract base class. This class is |
---|
| 2225 | the base class for all the model classes. It sorts out the energy |
---|
| 2226 | range for the models and provides class utilities. The |
---|
| 2227 | <emphasis>G4HadronicInteraction</emphasis> class provides the |
---|
| 2228 | <literal>Set/GetMinEnergy</literal> and the <literal>Set/GetMaxEnergy</literal> |
---|
| 2229 | functions which determine the minimum and maximum energy range for |
---|
| 2230 | the model. An energy range can be set for a specific element, a |
---|
| 2231 | specific material, or for general applicability: |
---|
| 2232 | |
---|
| 2233 | <informalexample> |
---|
| 2234 | <programlisting> |
---|
| 2235 | void SetMinEnergy( G4double anEnergy, G4Element *anElement ) |
---|
| 2236 | void SetMinEnergy( G4double anEnergy, G4Material *aMaterial ) |
---|
| 2237 | void SetMinEnergy( const G4double anEnergy ) |
---|
| 2238 | void SetMaxEnergy( G4double anEnergy, G4Element *anElement ) |
---|
| 2239 | void SetMaxEnergy( G4double anEnergy, G4Material *aMaterial ) |
---|
| 2240 | void SetMaxEnergy( const G4double anEnergy ) |
---|
| 2241 | </programlisting> |
---|
| 2242 | </informalexample> |
---|
| 2243 | </para> |
---|
| 2244 | |
---|
| 2245 | <!-- ******* Bridgehead ******* --> |
---|
| 2246 | <bridgehead renderas='sect4'> |
---|
| 2247 | Which models are there, and what are the defaults |
---|
| 2248 | </bridgehead> |
---|
| 2249 | |
---|
| 2250 | <para> |
---|
| 2251 | In Geant4, any model can be run together with any other model |
---|
| 2252 | without the need for the implementation of a special interface, or |
---|
| 2253 | batch suite, and the ranges of applicability for the different |
---|
| 2254 | models can be steered at initialisation time. This way, highly |
---|
| 2255 | specialised models (valid only for one material and particle, and |
---|
| 2256 | applicable only in a very restricted energy range) can be used in |
---|
| 2257 | the same application, together with more general code, in a |
---|
| 2258 | coherent fashion. |
---|
| 2259 | </para> |
---|
| 2260 | |
---|
| 2261 | <para> |
---|
| 2262 | Each model has an intrinsic range of applicability, and the |
---|
| 2263 | model chosen for a simulation depends very much on the use-case. |
---|
| 2264 | Consequently, there are no ``defaults''. However, physics lists are |
---|
| 2265 | provided which specify sets of models for various purposes. |
---|
| 2266 | </para> |
---|
| 2267 | |
---|
| 2268 | <para> |
---|
| 2269 | Three types of hadronic shower models have been implemented: |
---|
| 2270 | parametrisation driven models, data driven models, and theory |
---|
| 2271 | driven models. |
---|
| 2272 | |
---|
| 2273 | <itemizedlist spacing="compact"> |
---|
| 2274 | <listitem><para> |
---|
| 2275 | Parametrisation driven models are used for all processes |
---|
| 2276 | pertaining to particles coming to rest, and interacting with the |
---|
| 2277 | nucleus. For particles in flight, two sets of models exist for |
---|
| 2278 | inelastic scattering; low energy, and high energy models. Both sets |
---|
| 2279 | are based originally on the <emphasis role="bold">GHEISHA</emphasis> |
---|
| 2280 | package of Geant3.21, |
---|
| 2281 | and the original approaches to primary interaction, nuclear |
---|
| 2282 | excitation, intra-nuclear cascade and evaporation is kept. The |
---|
| 2283 | models are located in the sub-directories |
---|
| 2284 | <literal>hadronics/models/low_energy</literal> and |
---|
| 2285 | <literal>hadronics/models/high_energy</literal>. The low energy models are |
---|
| 2286 | targeted towards energies below 20 GeV; the high energy models |
---|
| 2287 | cover the energy range from 20 GeV to O(TeV). Fission, capture and |
---|
| 2288 | coherent elastic scattering are also modeled through parametrised |
---|
| 2289 | models. |
---|
| 2290 | </para></listitem> |
---|
| 2291 | <listitem><para> |
---|
| 2292 | Data driven models are available for the transport of low |
---|
| 2293 | energy neutrons in matter in sub-directory |
---|
| 2294 | <literal>hadronics/models/neutron_hp</literal>. The modeling is based |
---|
| 2295 | on the data formats of <emphasis role="bold">ENDF/B-VI</emphasis>, |
---|
| 2296 | and all distributions of this standard data format are implemented. |
---|
| 2297 | The data sets used are selected from data libraries that conform to |
---|
| 2298 | these standard formats. The file system is used in order to allow granular |
---|
| 2299 | access to, and flexibility in, the use of the cross sections for different |
---|
| 2300 | isotopes, and channels. The energy coverage of these models is from |
---|
| 2301 | thermal energies to 20 MeV. |
---|
| 2302 | </para></listitem> |
---|
| 2303 | <listitem><para> |
---|
| 2304 | Theory driven models are available for inelastic scattering in |
---|
| 2305 | a first implementation, covering the full energy range of LHC |
---|
| 2306 | experiments. They are located in sub-directory |
---|
| 2307 | <literal>hadronics/models/generator</literal>. The current philosophy |
---|
| 2308 | implies the usage of parton string models at high energies, of |
---|
| 2309 | intra-nuclear transport models at intermediate energies, and of |
---|
| 2310 | statistical break-up models for de-excitation. |
---|
| 2311 | </para></listitem> |
---|
| 2312 | </itemizedlist> |
---|
| 2313 | </para> |
---|
| 2314 | |
---|
| 2315 | </sect3> |
---|
| 2316 | </sect2> |
---|
| 2317 | |
---|
| 2318 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 2319 | <sect2 id="sect.PhysProc.Decay"> |
---|
| 2320 | <title> |
---|
| 2321 | Particle Decay Process |
---|
| 2322 | </title> |
---|
| 2323 | |
---|
| 2324 | <para> |
---|
| 2325 | This section briefly introduces decay processes installed in |
---|
| 2326 | Geant4. For details of the implementation of particle decays, |
---|
| 2327 | please refer to the |
---|
| 2328 | <ulink url="http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/PhysicsReferenceManual/html/PhysicsReferenceManual.html"> |
---|
| 2329 | <emphasis role="bold">Physics Reference Manual</emphasis></ulink>. |
---|
| 2330 | </para> |
---|
| 2331 | |
---|
| 2332 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 2333 | <sect3 id="sect.PhysProc.Decay.Class"> |
---|
| 2334 | <title> |
---|
| 2335 | Particle Decay Class |
---|
| 2336 | </title> |
---|
| 2337 | |
---|
| 2338 | <para> |
---|
| 2339 | Geant4 provides a <emphasis>G4Decay</emphasis> class for both ``at rest'' and |
---|
| 2340 | ``in flight'' particle decays. <emphasis>G4Decay</emphasis> can be applied to all |
---|
| 2341 | particles except: |
---|
| 2342 | |
---|
| 2343 | <variablelist> |
---|
| 2344 | <varlistentry> |
---|
| 2345 | <term> |
---|
| 2346 | massless particles, i.e., |
---|
| 2347 | </term> |
---|
| 2348 | <listitem> |
---|
| 2349 | <literal>G4ParticleDefinition::thePDGMass <= 0</literal> |
---|
| 2350 | </listitem> |
---|
| 2351 | </varlistentry> |
---|
| 2352 | <varlistentry> |
---|
| 2353 | <term> |
---|
| 2354 | particles with ``negative'' life time, i.e., |
---|
| 2355 | </term> |
---|
| 2356 | <listitem> |
---|
| 2357 | <literal>G4ParticleDefinition::thePDGLifeTime < 0</literal> |
---|
| 2358 | </listitem> |
---|
| 2359 | </varlistentry> |
---|
| 2360 | <varlistentry> |
---|
| 2361 | <term> |
---|
| 2362 | shortlived particles, i.e., |
---|
| 2363 | </term> |
---|
| 2364 | <listitem> |
---|
| 2365 | <literal>G4ParticleDefinition::fShortLivedFlag = True</literal> |
---|
| 2366 | </listitem> |
---|
| 2367 | </varlistentry> |
---|
| 2368 | </variablelist> |
---|
| 2369 | </para> |
---|
| 2370 | |
---|
| 2371 | <para> |
---|
| 2372 | Decay for some particles may be switched on or off by using |
---|
| 2373 | <literal>G4ParticleDefinition::SetPDGStable()</literal> as well as |
---|
| 2374 | <literal>ActivateProcess()</literal> and <literal>InActivateProcess()</literal> |
---|
| 2375 | methods of <emphasis>G4ProcessManager</emphasis>. |
---|
| 2376 | </para> |
---|
| 2377 | |
---|
| 2378 | <para> |
---|
| 2379 | <emphasis>G4Decay</emphasis> proposes the step length (or step time for |
---|
| 2380 | <literal>AtRest</literal>) according to the lifetime of the particle unless |
---|
| 2381 | <literal>PreAssignedDecayProperTime</literal> is defined in |
---|
| 2382 | <emphasis>G4DynamicParticle</emphasis>. |
---|
| 2383 | </para> |
---|
| 2384 | |
---|
| 2385 | <para> |
---|
| 2386 | The <emphasis>G4Decay</emphasis> class itself does not define decay modes of |
---|
| 2387 | the particle. Geant4 provides two ways of doing this: |
---|
| 2388 | |
---|
| 2389 | <itemizedlist spacing="compact"> |
---|
| 2390 | <listitem><para> |
---|
| 2391 | using <emphasis>G4DecayChannel</emphasis> in <emphasis>G4DecayTable</emphasis>, |
---|
| 2392 | and |
---|
| 2393 | </para></listitem> |
---|
| 2394 | <listitem><para> |
---|
| 2395 | using <literal>thePreAssignedDecayProducts</literal> of |
---|
| 2396 | <emphasis>G4DynamicParticle</emphasis> |
---|
| 2397 | </para></listitem> |
---|
| 2398 | </itemizedlist> |
---|
| 2399 | </para> |
---|
| 2400 | |
---|
| 2401 | <para> |
---|
| 2402 | The <emphasis>G4Decay</emphasis> class calculates the |
---|
| 2403 | <literal>PhysicalInteractionLength</literal> and boosts decay products |
---|
| 2404 | created by <emphasis>G4VDecayChannel</emphasis> or event generators. See below |
---|
| 2405 | for information on the determination of the decay modes. |
---|
| 2406 | </para> |
---|
| 2407 | |
---|
| 2408 | <para> |
---|
| 2409 | An object of <emphasis>G4Decay</emphasis> can be shared by particles. |
---|
| 2410 | Registration of the decay process to particles in the |
---|
| 2411 | <literal>ConstructPhysics</literal> method of <emphasis>PhysicsList</emphasis> |
---|
| 2412 | (see <xref linkend="sect.HowToSpecPhysProc.SpecPhysProc" />) |
---|
| 2413 | is shown in <xref linkend="programlist_PhysProc_4" />. |
---|
| 2414 | |
---|
| 2415 | <example id="programlist_PhysProc_4"> |
---|
| 2416 | <title> |
---|
| 2417 | Registration of the decay process to particles in the |
---|
| 2418 | <literal>ConstructPhysics</literal> method of <emphasis>PhysicsList</emphasis>. |
---|
| 2419 | </title> |
---|
| 2420 | |
---|
| 2421 | <programlisting> |
---|
| 2422 | #include "G4Decay.hh" |
---|
| 2423 | void ExN02PhysicsList::ConstructGeneral() |
---|
| 2424 | { |
---|
| 2425 | // Add Decay Process |
---|
| 2426 | G4Decay* theDecayProcess = new G4Decay(); |
---|
| 2427 | theParticleIterator->reset(); |
---|
| 2428 | while( (*theParticleIterator)() ){ |
---|
| 2429 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
| 2430 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
| 2431 | if (theDecayProcess->IsApplicable(*particle)) { |
---|
| 2432 | pmanager ->AddProcess(theDecayProcess); |
---|
| 2433 | // set ordering for PostStepDoIt and AtRestDoIt |
---|
| 2434 | pmanager ->SetProcessOrdering(theDecayProcess, idxPostStep); |
---|
| 2435 | pmanager ->SetProcessOrdering(theDecayProcess, idxAtRest); |
---|
| 2436 | } |
---|
| 2437 | } |
---|
| 2438 | } |
---|
| 2439 | </programlisting> |
---|
| 2440 | </example> |
---|
| 2441 | </para> |
---|
| 2442 | |
---|
| 2443 | </sect3> |
---|
| 2444 | |
---|
| 2445 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 2446 | <sect3 id="sect.PhysProc.Decay.Table"> |
---|
| 2447 | <title> |
---|
| 2448 | Decay Table |
---|
| 2449 | </title> |
---|
| 2450 | |
---|
| 2451 | <para> |
---|
| 2452 | Each particle has its <emphasis>G4DecayTable</emphasis>, which stores information |
---|
| 2453 | on the decay modes of the particle. Each decay mode, with its |
---|
| 2454 | branching ratio, corresponds to an object of various ``decay |
---|
| 2455 | channel'' classes derived from <emphasis>G4VDecayChannel</emphasis>. Default |
---|
| 2456 | decay modes are created in the constructors of particle classes. |
---|
| 2457 | For example, the decay table of the neutral pion has |
---|
| 2458 | <emphasis>G4PhaseSpaceDecayChannel</emphasis> and |
---|
| 2459 | <emphasis>G4DalitzDecayChannel</emphasis> as follows: |
---|
| 2460 | |
---|
| 2461 | <informalexample> |
---|
| 2462 | <programlisting> |
---|
| 2463 | // create a decay channel |
---|
| 2464 | G4VDecayChannel* mode; |
---|
| 2465 | // pi0 -> gamma + gamma |
---|
| 2466 | mode = new G4PhaseSpaceDecayChannel("pi0",0.988,2,"gamma","gamma"); |
---|
| 2467 | table->Insert(mode); |
---|
| 2468 | // pi0 -> gamma + e+ + e- |
---|
| 2469 | mode = new G4DalitzDecayChannel("pi0",0.012,"e-","e+"); |
---|
| 2470 | table->Insert(mode); |
---|
| 2471 | </programlisting> |
---|
| 2472 | </informalexample> |
---|
| 2473 | </para> |
---|
| 2474 | |
---|
| 2475 | <para> |
---|
| 2476 | Decay modes and branching ratios defined in Geant4 are listed in |
---|
| 2477 | <xref linkend="sect.Parti.Def" />. |
---|
| 2478 | </para> |
---|
| 2479 | |
---|
[1208] | 2480 | <para> |
---|
| 2481 | Branching ratios and life time can be set in tracking time. |
---|
| 2482 | <informalexample> |
---|
| 2483 | <programlisting> |
---|
| 2484 | // set lifetime |
---|
| 2485 | G4Neutron::Neutron()->SetPDGLifeTime(885.7*second); |
---|
| 2486 | // allow neutron decay |
---|
| 2487 | G4Neutron::Neutron()->SetPDGStable(false); |
---|
| 2488 | </programlisting> |
---|
| 2489 | </informalexample> |
---|
[1211] | 2490 | </para> |
---|
[1208] | 2491 | |
---|
[1211] | 2492 | <para> |
---|
[1208] | 2493 | Branching ratios and life time can be modified by using user commands, also. |
---|
| 2494 | </para> |
---|
| 2495 | |
---|
[1211] | 2496 | <para> |
---|
| 2497 | <emphasis role="bold">Example: Set 100% br for dalitz decay of pi0</emphasis> |
---|
| 2498 | |
---|
| 2499 | <informalexample> |
---|
| 2500 | <programlisting> |
---|
| 2501 | Idle> /particle/select pi0 |
---|
| 2502 | Idle> /particle/property/decay/select 0 |
---|
| 2503 | Idle> /particle/property/decay/br 0 |
---|
| 2504 | Idle> /particle/property/decay/select 1 |
---|
| 2505 | Idle> /particle/property/decay/br 1 |
---|
| 2506 | Idle> /particle/property/decay/dump |
---|
| 2507 | G4DecayTable: pi0 |
---|
| 2508 | 0: BR: 0 [Phase Space] : gamma gamma |
---|
| 2509 | 1: BR: 1 [Dalitz Decay] : gamma e- e+ |
---|
| 2510 | </programlisting> |
---|
| 2511 | </informalexample> |
---|
| 2512 | |
---|
| 2513 | </para> |
---|
| 2514 | |
---|
[904] | 2515 | </sect3> |
---|
| 2516 | |
---|
| 2517 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 2518 | <sect3 id="sect.PhysProc.Decay.PreAssgn"> |
---|
| 2519 | <title> |
---|
| 2520 | Pre-assigned Decay Modes by Event Generators |
---|
| 2521 | </title> |
---|
| 2522 | |
---|
| 2523 | <para> |
---|
| 2524 | Decays of heavy flavor particles such as B mesons are very complex, |
---|
| 2525 | with many varieties of decay modes and decay mechanisms. There are |
---|
| 2526 | many models for heavy particle decay provided by various event |
---|
| 2527 | generators and it is impossible to define all the decay modes of |
---|
| 2528 | heavy particles by using <emphasis>G4VDecayChannel</emphasis>. In other words, |
---|
| 2529 | decays of heavy particles cannot be defined by the Geant4 decay |
---|
| 2530 | process, but should be defined by event generators or other |
---|
| 2531 | external packages. Geant4 provides two ways to do this: |
---|
| 2532 | <literal>pre-assigned decay mode</literal> and <literal>external decayer</literal>. |
---|
| 2533 | </para> |
---|
| 2534 | |
---|
| 2535 | <para> |
---|
| 2536 | In the latter approach, the class <emphasis>G4VExtDecayer</emphasis> is used |
---|
| 2537 | for the interface to an external package which defines decay modes |
---|
| 2538 | for a particle. If an instance of <emphasis>G4VExtDecayer</emphasis> is attached |
---|
| 2539 | to <emphasis>G4Decay</emphasis>, daughter particles will be generated by the |
---|
| 2540 | external decay handler. |
---|
| 2541 | </para> |
---|
| 2542 | |
---|
| 2543 | <para> |
---|
| 2544 | In the former case, decays of heavy particles are simulated by |
---|
| 2545 | an event generator and the primary event contains the decay |
---|
| 2546 | information. <emphasis>G4VPrimaryGenerator</emphasis> automatically attaches any |
---|
| 2547 | daughter particles to the parent particle as the |
---|
| 2548 | PreAssignedDecayProducts member of <emphasis>G4DynamicParticle</emphasis>. |
---|
| 2549 | <emphasis>G4Decay</emphasis> adopts these pre-assigned daughter particles instead |
---|
| 2550 | of asking <emphasis>G4VDecayChannel</emphasis> to generate decay products. |
---|
| 2551 | </para> |
---|
| 2552 | |
---|
| 2553 | <para> |
---|
| 2554 | In addition, the user may assign a <literal>pre-assigned</literal> decay |
---|
| 2555 | time for a specific track in its rest frame (i.e. decay time is |
---|
| 2556 | defined in the proper time) by using the |
---|
| 2557 | <emphasis>G4PrimaryParticle::SetProperTime()</emphasis> method. |
---|
| 2558 | <emphasis>G4VPrimaryGenerator</emphasis> sets the PreAssignedDecayProperTime |
---|
| 2559 | member of <emphasis>G4DynamicParticle</emphasis>. <emphasis>G4Decay</emphasis> |
---|
| 2560 | uses this decay time instead of the life time of the particle type. |
---|
| 2561 | </para> |
---|
| 2562 | |
---|
| 2563 | </sect3> |
---|
| 2564 | </sect2> |
---|
| 2565 | |
---|
| 2566 | |
---|
| 2567 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 2568 | <sect2 id="sect.PhysProc.PhotoHad"> |
---|
| 2569 | <title> |
---|
| 2570 | Photolepton-hadron Processes |
---|
| 2571 | </title> |
---|
| 2572 | |
---|
| 2573 | <para> |
---|
| 2574 | To be delivered. |
---|
| 2575 | </para> |
---|
| 2576 | |
---|
| 2577 | </sect2> |
---|
| 2578 | |
---|
| 2579 | |
---|
| 2580 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 2581 | <sect2 id="sect.PhysProc.Photo"> |
---|
| 2582 | <title> |
---|
| 2583 | Optical Photon Processes |
---|
| 2584 | </title> |
---|
| 2585 | |
---|
| 2586 | <para> |
---|
| 2587 | A photon is considered to be <emphasis>optical</emphasis> when its wavelength |
---|
| 2588 | is much greater than the typical atomic spacing. In GEANT4 optical |
---|
| 2589 | photons are treated as a class of particle distinct from their |
---|
| 2590 | higher energy <emphasis>gamma</emphasis> cousins. This implementation allows the |
---|
| 2591 | wave-like properties of electromagnetic radiation to be |
---|
| 2592 | incorporated into the optical photon process. Because this |
---|
| 2593 | theoretical description breaks down at higher energies, there is no |
---|
| 2594 | smooth transition as a function of energy between the optical |
---|
| 2595 | photon and gamma particle classes. |
---|
| 2596 | </para> |
---|
| 2597 | |
---|
| 2598 | <para> |
---|
| 2599 | For the simulation of optical photons to work correctly in |
---|
| 2600 | GEANT4, they must be imputed a linear polarization. This is unlike |
---|
| 2601 | most other particles in GEANT4 but is automatically and correctly |
---|
| 2602 | done for optical photons that are generated as secondaries by |
---|
| 2603 | existing processes in GEANT4. Not so, if the user wishes to start |
---|
| 2604 | optical photons as primary particles. In this case, the user must |
---|
| 2605 | set the linear polarization using particle gun methods, the General |
---|
| 2606 | Particle Source, or his/her PrimaryGeneratorAction. For an |
---|
| 2607 | unpolarized source, the linear polarization should be sampled |
---|
| 2608 | randomly for each new primary photon. |
---|
| 2609 | </para> |
---|
| 2610 | |
---|
| 2611 | <para> |
---|
| 2612 | The GEANT4 catalogue of processes at optical wavelengths |
---|
| 2613 | includes refraction and reflection at medium boundaries, bulk |
---|
| 2614 | absorption and Rayleigh scattering. Processes which produce optical |
---|
| 2615 | photons include the Cerenkov effect, transition radiation and |
---|
| 2616 | scintillation. Optical photons are generated in GEANT4 without |
---|
| 2617 | energy conservation and their energy must therefore not be tallied |
---|
| 2618 | as part of the energy balance of an event. |
---|
| 2619 | </para> |
---|
| 2620 | |
---|
| 2621 | <para> |
---|
| 2622 | The optical properties of the medium which are key to the |
---|
| 2623 | implementation of these types of processes are stored as entries in |
---|
| 2624 | a <literal>G4MaterialPropertiesTable</literal> which is linked to the |
---|
| 2625 | <literal>G4Material</literal> in question. These properties may be constants |
---|
| 2626 | or they may be expressed as a function of the photon's wavelength. |
---|
| 2627 | This table is a private data member of the <literal>G4Material</literal> |
---|
| 2628 | class. The <literal>G4MaterialPropertiesTable</literal> is implemented as a |
---|
| 2629 | hash directory, in which each entry consists of a <emphasis>value</emphasis> and |
---|
| 2630 | a <emphasis>key</emphasis>. The key is used to quickly and efficiently retrieve |
---|
| 2631 | the corresponding value. All values in the dictionary are either |
---|
| 2632 | instantiations of <literal>G4double</literal> or the class |
---|
| 2633 | <literal>G4MaterialPropertyVector</literal>, and all keys are of type |
---|
| 2634 | <literal>G4String</literal>. |
---|
| 2635 | </para> |
---|
| 2636 | |
---|
| 2637 | <para> |
---|
| 2638 | A <literal>G4MaterialPropertyVector</literal> is composed of |
---|
| 2639 | instantiations of the class <literal>G4MPVEntry</literal>. The |
---|
| 2640 | <literal>G4MPVEntry</literal> is a pair of numbers, which in the case of an |
---|
| 2641 | optical property, are the photon momentum and corresponding |
---|
| 2642 | property value. The <literal>G4MaterialPropertyVector</literal> is |
---|
| 2643 | implemented as a <literal>G4std::vector</literal>, with the sorting operation |
---|
| 2644 | defined as |
---|
| 2645 | MPVEntry<subscript>1</subscript> < MPVEntry<subscript>2</subscript> == |
---|
| 2646 | photon_momentum<subscript>1</subscript> < photon_momentum<subscript>2</subscript>. |
---|
| 2647 | This results in all <literal>G4MaterialPropertyVector</literal>s being sorted in |
---|
| 2648 | ascending order of photon momenta. It is possible for the user to |
---|
| 2649 | add as many material (optical) properties to the material as he |
---|
| 2650 | wishes using the methods supplied by the |
---|
| 2651 | <literal>G4MaterialPropertiesTable</literal> class. An example of this is |
---|
| 2652 | shown in <xref linkend="programlist_PhysProc_5" />. |
---|
| 2653 | |
---|
| 2654 | <example id="programlist_PhysProc_5"> |
---|
| 2655 | <title> |
---|
| 2656 | Optical properties added to a <literal>G4MaterialPropertiesTable</literal> |
---|
| 2657 | and linked to a <literal>G4Material</literal> |
---|
| 2658 | </title> |
---|
| 2659 | |
---|
| 2660 | <programlisting> |
---|
| 2661 | const G4int NUMENTRIES = 32; |
---|
| 2662 | |
---|
| 2663 | G4double ppckov[NUMENTRIES] = {2.034*eV, ......, 4.136*eV}; |
---|
| 2664 | G4double rindex[NUMENTRIES] = {1.3435, ......, 1.3608}; |
---|
| 2665 | G4double absorption[NUMENTRIES] = {344.8*cm, ......, 1450.0*cm]; |
---|
| 2666 | |
---|
| 2667 | G4MaterialPropertiesTable *MPT = new G4MaterialPropertiesTable(); |
---|
| 2668 | |
---|
| 2669 | MPT -> AddConstProperty("SCINTILLATIONYIELD",100./MeV); |
---|
| 2670 | |
---|
| 2671 | MPT -> AddProperty("RINDEX",ppckov,rindex,NUMENTRIES}; |
---|
| 2672 | MPT -> AddProperty("ABSLENGTH",ppckov,absorption,NUMENTRIES}; |
---|
| 2673 | |
---|
| 2674 | scintillator -> SetMaterialPropertiesTable(MPT); |
---|
| 2675 | </programlisting> |
---|
| 2676 | </example> |
---|
| 2677 | </para> |
---|
| 2678 | |
---|
| 2679 | |
---|
| 2680 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 2681 | <sect3 id="sect.PhysProc.Photo.Cerenkov"> |
---|
| 2682 | <title> |
---|
| 2683 | Generation of Photons in |
---|
| 2684 | <literal>processes/electromagnetic/xrays</literal> - Cerenkov Effect |
---|
| 2685 | </title> |
---|
| 2686 | |
---|
| 2687 | <para> |
---|
| 2688 | The radiation of Cerenkov light occurs when a charged particle |
---|
| 2689 | moves through a dispersive medium faster than the group velocity of |
---|
| 2690 | light in that medium. Photons are emitted on the surface of a cone, |
---|
| 2691 | whose opening angle with respect to the particle's instantaneous |
---|
| 2692 | direction decreases as the particle slows down. At the same time, |
---|
| 2693 | the frequency of the photons emitted increases, and the number |
---|
| 2694 | produced decreases. When the particle velocity drops below the |
---|
| 2695 | local speed of light, the radiation ceases and the emission cone |
---|
| 2696 | angle collapses to zero. The photons produced by this process have |
---|
| 2697 | an inherent polarization perpendicular to the cone's surface at |
---|
| 2698 | production. |
---|
| 2699 | </para> |
---|
| 2700 | |
---|
| 2701 | <para> |
---|
| 2702 | The flux, spectrum, polarization and emission of Cerenkov |
---|
| 2703 | radiation in the <literal>AlongStepDoIt</literal> method of the class |
---|
| 2704 | <literal>G4Cerenkov</literal> follow well-known formulae, with two inherent |
---|
| 2705 | computational limitations. The first arises from step-wise |
---|
| 2706 | simulation, and the second comes from the requirement that |
---|
| 2707 | numerical integration calculate the average number of Cerenkov |
---|
| 2708 | photons per step. The process makes use of a |
---|
| 2709 | <literal>G4PhysicsTable</literal> which contains incremental integrals to |
---|
| 2710 | expedite this calculation. |
---|
| 2711 | </para> |
---|
| 2712 | |
---|
| 2713 | <para> |
---|
| 2714 | The time and position of Cerenkov photon emission are calculated |
---|
| 2715 | from quantities known at the beginning of a charged particle's |
---|
| 2716 | step. The step is assumed to be rectilinear even in the presence of |
---|
| 2717 | a magnetic field. The user may limit the step size by specifying a |
---|
| 2718 | maximum (average) number of Cerenkov photons created during the |
---|
| 2719 | step, using the <literal>SetMaxNumPhotonsPerStep(const G4int |
---|
| 2720 | NumPhotons)</literal> method. The actual number generated will |
---|
| 2721 | necessarily be different due to the Poissonian nature of the |
---|
| 2722 | production. In the present implementation, the production density |
---|
| 2723 | of photons is distributed evenly along the particle's track |
---|
| 2724 | segment, even if the particle has slowed significantly during the |
---|
| 2725 | step. |
---|
| 2726 | </para> |
---|
| 2727 | |
---|
| 2728 | <para> |
---|
| 2729 | The frequently very large number of secondaries produced in a |
---|
| 2730 | single step (about 300/cm in water), compelled the idea in |
---|
| 2731 | GEANT3.21 of suspending the primary particle until all its progeny |
---|
| 2732 | have been tracked. Despite the fact that GEANT4 employs dynamic |
---|
| 2733 | memory allocation and thus does not suffer from the limitations of |
---|
| 2734 | GEANT3.21 with its fixed large initial ZEBRA store, GEANT4 |
---|
| 2735 | nevertheless provides for an analogous functionality with the |
---|
| 2736 | public method <literal>SetTrackSecondariesFirst</literal>. An example of the |
---|
| 2737 | registration of the Cerenkov process is given in |
---|
| 2738 | <xref linkend="programlist_PhysProc_6" />. |
---|
| 2739 | |
---|
| 2740 | <example id="programlist_PhysProc_6"> |
---|
| 2741 | <title> |
---|
| 2742 | Registration of the Cerenkov process in <literal>PhysicsList</literal>. |
---|
| 2743 | </title> |
---|
| 2744 | |
---|
| 2745 | <programlisting> |
---|
| 2746 | #include "G4Cerenkov.hh" |
---|
| 2747 | |
---|
| 2748 | void ExptPhysicsList::ConstructOp(){ |
---|
| 2749 | |
---|
| 2750 | G4Cerenkov* theCerenkovProcess = new G4Cerenkov("Cerenkov"); |
---|
| 2751 | |
---|
| 2752 | G4int MaxNumPhotons = 300; |
---|
| 2753 | |
---|
| 2754 | theCerenkovProcess->SetTrackSecondariesFirst(true); |
---|
| 2755 | theCerenkovProcess->SetMaxNumPhotonsPerStep(MaxNumPhotons); |
---|
| 2756 | |
---|
| 2757 | theParticleIterator->reset(); |
---|
| 2758 | while( (*theParticleIterator)() ){ |
---|
| 2759 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
| 2760 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
| 2761 | G4String particleName = particle->GetParticleName(); |
---|
| 2762 | if (theCerenkovProcess->IsApplicable(*particle)) { |
---|
| 2763 | pmanager->AddContinuousProcess(theCerenkovProcess); |
---|
| 2764 | } |
---|
| 2765 | } |
---|
| 2766 | } |
---|
| 2767 | </programlisting> |
---|
| 2768 | </example> |
---|
| 2769 | </para> |
---|
| 2770 | |
---|
| 2771 | </sect3> |
---|
| 2772 | |
---|
| 2773 | |
---|
| 2774 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 2775 | <sect3 id="sect.PhysProc.Photo.Scinti"> |
---|
| 2776 | <title> |
---|
| 2777 | Generation of Photons in |
---|
| 2778 | <literal>processes/electromagnetic/xrays</literal> - Scintillation |
---|
| 2779 | </title> |
---|
| 2780 | |
---|
| 2781 | <para> |
---|
| 2782 | Every scintillating material has a characteristic light yield, |
---|
| 2783 | <literal>SCINTILLATIONYIELD</literal>, and an intrinsic resolution, |
---|
| 2784 | <literal>RESOLUTIONSCALE</literal>, which generally broadens the statistical |
---|
| 2785 | distribution of generated photons. A wider intrinsic resolution is |
---|
| 2786 | due to impurities which are typical for doped crystals like NaI(Tl) |
---|
| 2787 | and CsI(Tl). On the other hand, the intrinsic resolution can also |
---|
| 2788 | be narrower when the Fano factor plays a role. The actual number of |
---|
| 2789 | emitted photons during a step fluctuates around the mean number of |
---|
| 2790 | photons with a width given by |
---|
| 2791 | <literal>ResolutionScale*sqrt(MeanNumberOfPhotons)</literal>. The average |
---|
| 2792 | light yield, <literal>MeanNumberOfPhotons</literal>, has a linear dependence |
---|
| 2793 | on the local energy deposition, but it may be different for minimum |
---|
| 2794 | ionizing and non-minimum ionizing particles. |
---|
| 2795 | </para> |
---|
| 2796 | |
---|
| 2797 | <para> |
---|
| 2798 | A scintillator is also characterized by its photon emission |
---|
| 2799 | spectrum and by the exponential decay of its time spectrum. In |
---|
| 2800 | GEANT4 the scintillator can have a fast and a slow component. The |
---|
| 2801 | relative strength of the fast component as a fraction of total |
---|
| 2802 | scintillation yield is given by the <literal>YIELDRATIO</literal>. |
---|
| 2803 | Scintillation may be simulated by specifying these empirical |
---|
| 2804 | parameters for each material. It is sufficient to specify in the |
---|
| 2805 | user's <literal>DetectorConstruction</literal> class a relative spectral |
---|
| 2806 | distribution as a function of photon energy for the scintillating |
---|
| 2807 | material. An example of this is shown in |
---|
| 2808 | <xref linkend="programlist_PhysProc_7" /> |
---|
| 2809 | |
---|
| 2810 | <example id="programlist_PhysProc_7"> |
---|
| 2811 | <title> |
---|
| 2812 | Specification of scintillation properties in |
---|
| 2813 | <literal>DetectorConstruction</literal>. |
---|
| 2814 | </title> |
---|
| 2815 | <programlisting> |
---|
| 2816 | const G4int NUMENTRIES = 9; |
---|
| 2817 | G4double Scnt_PP[NUMENTRIES] = { 6.6*eV, 6.7*eV, 6.8*eV, 6.9*eV, |
---|
| 2818 | 7.0*eV, 7.1*eV, 7.2*eV, 7.3*eV, 7.4*eV }; |
---|
| 2819 | |
---|
| 2820 | G4double Scnt_FAST[NUMENTRIES] = { 0.000134, 0.004432, 0.053991, 0.241971, |
---|
| 2821 | 0.398942, 0.000134, 0.004432, 0.053991, |
---|
| 2822 | 0.241971 }; |
---|
| 2823 | G4double Scnt_SLOW[NUMENTRIES] = { 0.000010, 0.000020, 0.000030, 0.004000, |
---|
| 2824 | 0.008000, 0.005000, 0.020000, 0.001000, |
---|
| 2825 | 0.000010 }; |
---|
| 2826 | |
---|
| 2827 | G4Material* Scnt; |
---|
| 2828 | G4MaterialPropertiesTable* Scnt_MPT = new G4MaterialPropertiesTable(); |
---|
| 2829 | |
---|
| 2830 | Scnt_MPT->AddProperty("FASTCOMPONENT", Scnt_PP, Scnt_FAST, NUMENTRIES); |
---|
| 2831 | Scnt_MPT->AddProperty("SLOWCOMPONENT", Scnt_PP, Scnt_SLOW, NUMENTRIES); |
---|
| 2832 | |
---|
| 2833 | Scnt_MPT->AddConstProperty("SCINTILLATIONYIELD", 5000./MeV); |
---|
| 2834 | Scnt_MPT->AddConstProperty("RESOLUTIONSCALE", 2.0); |
---|
| 2835 | Scnt_MPT->AddConstProperty("FASTTIMECONSTANT", 1.*ns); |
---|
| 2836 | Scnt_MPT->AddConstProperty("SLOWTIMECONSTANT", 10.*ns); |
---|
| 2837 | Scnt_MPT->AddConstProperty("YIELDRATIO", 0.8); |
---|
| 2838 | |
---|
| 2839 | Scnt->SetMaterialPropertiesTable(Scnt_MPT); |
---|
| 2840 | </programlisting> |
---|
| 2841 | </example> |
---|
| 2842 | </para> |
---|
| 2843 | |
---|
| 2844 | <para> |
---|
| 2845 | In cases where the scintillation yield of a scintillator depends |
---|
| 2846 | on the particle type, different scintillation processes may be |
---|
| 2847 | defined for them. How this yield scales to the one specified for |
---|
| 2848 | the material is expressed with the |
---|
| 2849 | <literal>ScintillationYieldFactor</literal> in the user's |
---|
| 2850 | <literal>PhysicsList</literal> as shown in |
---|
| 2851 | <xref linkend="programlist_PhysProc_8" />. |
---|
| 2852 | In those cases where the fast to slow excitation ratio changes with particle |
---|
| 2853 | type, the method <literal>SetScintillationExcitationRatio</literal> can be |
---|
| 2854 | called for each scintillation process (see the advanced |
---|
| 2855 | underground_physics example). This overwrites the |
---|
| 2856 | <literal>YieldRatio</literal> obtained from the |
---|
| 2857 | <literal>G4MaterialPropertiesTable</literal>. |
---|
| 2858 | |
---|
| 2859 | <example id="programlist_PhysProc_8"> |
---|
| 2860 | <title> |
---|
| 2861 | Implementation of the scintillation process in |
---|
| 2862 | <literal>PhysicsList</literal>. |
---|
| 2863 | </title> |
---|
| 2864 | |
---|
| 2865 | <programlisting> |
---|
| 2866 | G4Scintillation* theMuonScintProcess = new G4Scintillation("Scintillation"); |
---|
| 2867 | |
---|
| 2868 | theMuonScintProcess->SetTrackSecondariesFirst(true); |
---|
| 2869 | theMuonScintProcess->SetScintillationYieldFactor(0.8); |
---|
| 2870 | |
---|
| 2871 | theParticleIterator->reset(); |
---|
| 2872 | while( (*theParticleIterator)() ){ |
---|
| 2873 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
| 2874 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
| 2875 | G4String particleName = particle->GetParticleName(); |
---|
| 2876 | if (theMuonScintProcess->IsApplicable(*particle)) { |
---|
| 2877 | if (particleName == "mu+") { |
---|
| 2878 | pmanager->AddProcess(theMuonScintProcess); |
---|
| 2879 | pmanager->SetProcessOrderingToLast(theMuonScintProcess, idxAtRest); |
---|
| 2880 | pmanager->SetProcessOrderingToLast(theMuonScintProcess, idxPostStep); |
---|
| 2881 | } |
---|
| 2882 | } |
---|
| 2883 | } |
---|
| 2884 | </programlisting> |
---|
| 2885 | </example> |
---|
| 2886 | </para> |
---|
| 2887 | |
---|
| 2888 | <para> |
---|
| 2889 | A Gaussian-distributed number of photons is generated according |
---|
| 2890 | to the energy lost during the step. A resolution scale of 1.0 |
---|
| 2891 | produces a statistical fluctuation around the average yield set |
---|
| 2892 | with <literal>AddConstProperty("SCINTILLATIONYIELD")</literal>, while values |
---|
| 2893 | > 1 broaden the fluctuation. A value of zero produces no |
---|
| 2894 | fluctuation. Each photon's frequency is sampled from the empirical |
---|
| 2895 | spectrum. The photons originate evenly along the track segment and |
---|
| 2896 | are emitted uniformly into 4π with a random linear polarization |
---|
| 2897 | and at times characteristic for the scintillation component. |
---|
| 2898 | </para> |
---|
| 2899 | |
---|
| 2900 | </sect3> |
---|
| 2901 | |
---|
| 2902 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 2903 | <sect3 id="sect.PhysProc.Photo.WaveShift"> |
---|
| 2904 | <title> |
---|
| 2905 | Generation of Photons in |
---|
| 2906 | <literal>processes/optical</literal> - Wavelength Shifting |
---|
| 2907 | </title> |
---|
| 2908 | |
---|
| 2909 | <para> |
---|
| 2910 | Wavelength Shifting (WLS) fibers are used in many high-energy |
---|
| 2911 | particle physics experiments. They absorb light at one wavelength |
---|
| 2912 | and re-emit light at a different wavelength and are used for |
---|
| 2913 | several reasons. For one, they tend to decrease the self-absorption |
---|
| 2914 | of the detector so that as much light reaches the PMTs as possible. |
---|
| 2915 | WLS fibers are also used to match the emission spectrum of the |
---|
| 2916 | detector with the input spectrum of the PMT. |
---|
| 2917 | </para> |
---|
| 2918 | |
---|
| 2919 | <para> |
---|
| 2920 | A WLS material is characterized by its photon absorption and |
---|
| 2921 | photon emission spectrum and by a possible time delay between the |
---|
| 2922 | absorption and re-emission of the photon. Wavelength Shifting may |
---|
| 2923 | be simulated by specifying these empirical parameters for each WLS |
---|
| 2924 | material in the simulation. It is sufficient to specify in the |
---|
| 2925 | user's <literal>DetectorConstruction</literal> class a relative spectral |
---|
| 2926 | distribution as a function of photon energy for the WLS material. |
---|
| 2927 | WLSABSLENGTH is the absorption length of the material as a function |
---|
| 2928 | of the photon's momentum. WLSCOMPONENT is the relative emission |
---|
| 2929 | spectrum of the material as a function of the photon's momentum, |
---|
| 2930 | and WLSTIMECONSTANT accounts for any time delay which may occur |
---|
| 2931 | between absorption and re-emission of the photon. An example is |
---|
| 2932 | shown in <xref linkend="programlist_PhysProc_9" />. |
---|
| 2933 | |
---|
| 2934 | <example id="programlist_PhysProc_9"> |
---|
| 2935 | <title> |
---|
| 2936 | Specification of WLS properties in <literal>DetectorConstruction</literal>. |
---|
| 2937 | </title> |
---|
| 2938 | |
---|
| 2939 | <programlisting> |
---|
| 2940 | const G4int nEntries = 9; |
---|
| 2941 | |
---|
| 2942 | G4double PhotonEnergy[nEntries] = { 6.6*eV, 6.7*eV, 6.8*eV, 6.9*eV, |
---|
| 2943 | 7.0*eV, 7.1*eV, 7.2*eV, 7.3*eV, 7.4*eV }; |
---|
| 2944 | |
---|
| 2945 | G4double RIndexFiber[nEntries] = |
---|
| 2946 | { 1.60, 1.60, 1.60, 1.60, 1.60, 1.60, 1.60, 1.60, 1.60 }; |
---|
| 2947 | G4double AbsFiber[nEntries] = |
---|
| 2948 | {0.1*mm,0.2*mm,0.3*mm,0.4*cm,1.0*cm,10*cm,1.0*m,10.0*m,10.0*m}; |
---|
| 2949 | G4double EmissionFiber[nEntries] = |
---|
| 2950 | {0.0, 0.0, 0.0, 0.1, 0.5, 1.0, 5.0, 10.0, 10.0 }; |
---|
| 2951 | |
---|
| 2952 | G4Material* WLSFiber; |
---|
| 2953 | G4MaterialPropertiesTable* MPTFiber = new G4MaterialPropertiesTable(); |
---|
| 2954 | |
---|
| 2955 | MPTFiber->AddProperty("RINDEX",PhotonEnergy,RIndexFiber,nEntries); |
---|
| 2956 | MPTFiber->AddProperty("WLSABSLENGTH",PhotonEnergy,AbsFiber,nEntries); |
---|
| 2957 | MPTFiber->AddProperty("WLSCOMPONENT",PhotonEnergy,EmissionFiber,nEntries); |
---|
| 2958 | MPTFiber->AddConstProperty("WLSTIMECONSTANT", 0.5*ns); |
---|
| 2959 | |
---|
| 2960 | WLSFiber->SetMaterialPropertiesTable(MPTFiber); |
---|
| 2961 | </programlisting> |
---|
| 2962 | </example> |
---|
| 2963 | </para> |
---|
| 2964 | |
---|
| 2965 | <para> |
---|
| 2966 | The process is defined in the PhysicsList in the usual way. The |
---|
| 2967 | process class name is G4OpWLS. It should be instantiated with |
---|
| 2968 | theWLSProcess = new G4OpWLS("OpWLS") and attached to the process |
---|
| 2969 | manager of the optical photon as a DiscreteProcess. The way the |
---|
| 2970 | WLSTIMECONSTANT is used depends on the time profile method chosen |
---|
| 2971 | by the user. If in the PhysicsList |
---|
| 2972 | theWLSProcess->UseTimeGenerator("exponential") option is set, |
---|
| 2973 | the time delay between absorption and re-emission of the photon is |
---|
| 2974 | sampled from an exponential distribution, with the decay term equal |
---|
| 2975 | to WLSTIMECONSTANT. If, on the other hand, |
---|
| 2976 | theWLSProcess->UseTimeGenerator("delta") is chosen, the time |
---|
| 2977 | delay is a delta function and equal to WLSTIMECONSTANT. The default |
---|
| 2978 | is "delta" in case the G4OpWLS::UseTimeGenerator(const G4String |
---|
| 2979 | name) method is not used. |
---|
| 2980 | </para> |
---|
| 2981 | |
---|
| 2982 | </sect3> |
---|
| 2983 | |
---|
| 2984 | |
---|
| 2985 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 2986 | <sect3 id="sect.PhysProc.Photo.Track"> |
---|
| 2987 | <title> |
---|
| 2988 | Tracking of Photons in <literal>processes/optical</literal> |
---|
| 2989 | </title> |
---|
| 2990 | |
---|
| 2991 | <!-- ******* Bridgehead ******* --> |
---|
| 2992 | <bridgehead renderas='sect4'> |
---|
| 2993 | Absorption |
---|
| 2994 | </bridgehead> |
---|
| 2995 | |
---|
| 2996 | <para> |
---|
| 2997 | The implementation of optical photon bulk absorption, |
---|
| 2998 | <literal>G4OpAbsorption</literal>, is trivial in that the process merely |
---|
| 2999 | kills the particle. The procedure requires the user to fill the |
---|
| 3000 | relevant <literal>G4MaterialPropertiesTable</literal> with empirical data for |
---|
| 3001 | the absorption length, using <literal>ABSLENGTH</literal> as the property key |
---|
| 3002 | in the public method <literal>AddProperty</literal>. The absorption length is |
---|
| 3003 | the average distance traveled by a photon before being absorpted by |
---|
| 3004 | the medium; i.e. it is the mean free path returned by the |
---|
| 3005 | <literal>GetMeanFreePath</literal> method. |
---|
| 3006 | </para> |
---|
| 3007 | |
---|
| 3008 | <!-- ******* Bridgehead ******* --> |
---|
| 3009 | <bridgehead renderas='sect4'> |
---|
| 3010 | Rayleigh Scattering |
---|
| 3011 | </bridgehead> |
---|
| 3012 | |
---|
| 3013 | <para> |
---|
| 3014 | The differential cross section in Rayleigh scattering, |
---|
| 3015 | σ/ω, is proportional |
---|
| 3016 | to cos<superscript>2</superscript>(&thetas;), |
---|
| 3017 | where &thetas; is the polar of the new polarization vector with |
---|
| 3018 | respect to the old polarization vector. The <literal>G4OpRayleigh</literal> |
---|
| 3019 | scattering process samples this angle accordingly and then |
---|
| 3020 | calculates the scattered photon's new direction by requiring that |
---|
| 3021 | it be perpendicular to the photon's new polarization in such a way |
---|
| 3022 | that the final direction, initial and final polarizations are all |
---|
| 3023 | in one plane. This process thus depends on the particle's |
---|
| 3024 | polarization (spin). The photon's polarization is a data member of |
---|
| 3025 | the <literal>G4DynamicParticle</literal> class. |
---|
| 3026 | </para> |
---|
| 3027 | |
---|
| 3028 | <para> |
---|
| 3029 | A photon which is not assigned a polarization at production, |
---|
| 3030 | either via the <literal>SetPolarization</literal> method of the |
---|
| 3031 | <literal>G4PrimaryParticle</literal> class, or indirectly with the |
---|
| 3032 | <literal>SetParticlePolarization</literal> method of the |
---|
| 3033 | <literal>G4ParticleGun</literal> class, may not be Rayleigh scattered. |
---|
| 3034 | Optical photons produced by the <literal>G4Cerenkov</literal> process have |
---|
| 3035 | inherently a polarization perpendicular to the cone's surface at |
---|
| 3036 | production. Scintillation photons have a random linear polarization |
---|
| 3037 | perpendicular to their direction. |
---|
| 3038 | </para> |
---|
| 3039 | |
---|
| 3040 | <para> |
---|
| 3041 | The process requires a <literal>G4MaterialPropertiesTable</literal> to be |
---|
| 3042 | filled by the user with Rayleigh scattering length data. The |
---|
| 3043 | Rayleigh scattering attenuation length is the average distance |
---|
| 3044 | traveled by a photon before it is Rayleigh scattered in the medium |
---|
| 3045 | and it is the distance returned by the <literal>GetMeanFreePath</literal> |
---|
| 3046 | method. The <literal>G4OpRayleigh</literal> class provides a |
---|
| 3047 | <literal>RayleighAttenuationLengthGenerator</literal> method which calculates |
---|
| 3048 | the attenuation coefficient of a medium following the |
---|
| 3049 | Einstein-Smoluchowski formula whose derivation requires the use of |
---|
| 3050 | statistical mechanics, includes temperature, and depends on the |
---|
| 3051 | isothermal compressibility of the medium. This generator is |
---|
| 3052 | convenient when the Rayleigh attenuation length is not known from |
---|
| 3053 | measurement but may be calculated from first principles using the |
---|
| 3054 | above material constants. For a medium named <emphasis>Water</emphasis> and no |
---|
| 3055 | Rayleigh scattering attenutation length specified by the user, the |
---|
| 3056 | program automatically calls the |
---|
| 3057 | <literal>RayleighAttenuationLengthGenerator</literal> |
---|
| 3058 | which calculates it for 10 degrees Celsius liquid water. |
---|
| 3059 | </para> |
---|
| 3060 | |
---|
| 3061 | <!-- ******* Bridgehead ******* --> |
---|
| 3062 | <bridgehead renderas='sect4'> |
---|
| 3063 | Boundary Process |
---|
| 3064 | </bridgehead> |
---|
| 3065 | |
---|
| 3066 | <para> |
---|
| 3067 | Reference: E. Hecht and A. Zajac, Optics |
---|
| 3068 | <citation> |
---|
| 3069 | <xref linkend="biblio.hecht1974" endterm="biblio.hecht1974.abbrev" /> |
---|
| 3070 | </citation> |
---|
| 3071 | </para> |
---|
| 3072 | |
---|
| 3073 | <para> |
---|
| 3074 | For the simple case of a perfectly smooth interface between two |
---|
| 3075 | dielectric materials, all the user needs to provide are the |
---|
| 3076 | refractive indices of the two materials stored in their respective |
---|
| 3077 | <literal>G4MaterialPropertiesTable</literal>. In all other cases, the optical |
---|
| 3078 | boundary process design relies on the concept of <emphasis>surfaces</emphasis>. |
---|
| 3079 | The information is split into two classes. One class in the |
---|
| 3080 | material category keeps information about the physical properties |
---|
| 3081 | of the surface itself, and a second class in the geometry category |
---|
| 3082 | holds pointers to the relevant physical and logical volumes |
---|
| 3083 | involved and has an association to the physical class. Surface |
---|
| 3084 | objects of the second type are stored in a related table and can be |
---|
| 3085 | retrieved by either specifying the two ordered pairs of physical |
---|
| 3086 | volumes touching at the surface, or by the logical volume entirely |
---|
| 3087 | surrounded by this surface. The former is called a <emphasis>border |
---|
| 3088 | surface</emphasis> while the latter is referred to as the <emphasis>skin |
---|
| 3089 | surface</emphasis>. This second type of surface is useful in situations |
---|
| 3090 | where a volume is coded with a reflector and is placed into many |
---|
| 3091 | different mother volumes. A limitation is that the skin surface can |
---|
| 3092 | only have one and the same optical property for all of the enclosed |
---|
| 3093 | volume's sides. The border surface is an ordered pair of physical |
---|
| 3094 | volumes, so in principle, the user can choose different optical |
---|
| 3095 | properties for photons arriving from the reverse side of the same |
---|
| 3096 | interface. For the optical boundary process to use a border |
---|
| 3097 | surface, the two volumes must have been positioned with |
---|
| 3098 | <literal>G4PVPlacement</literal>. The ordered combination can exist at many |
---|
| 3099 | places in the simulation. When the surface concept is not needed, |
---|
| 3100 | and a perfectly smooth surface exists beteen two dielectic |
---|
| 3101 | materials, the only relevant property is the index of refraction, a |
---|
| 3102 | quantity stored with the material, and no restriction exists on how |
---|
| 3103 | the volumes were positioned. |
---|
| 3104 | </para> |
---|
| 3105 | |
---|
| 3106 | <para> |
---|
| 3107 | The physical surface object also specifies which model the |
---|
| 3108 | boundary process should use to simulate interactions with that |
---|
| 3109 | surface. In addition, the physical surface can have a material |
---|
| 3110 | property table all its own. The usage of this table allows all |
---|
| 3111 | specular constants to be wavelength dependent. In case the surface |
---|
| 3112 | is painted or wrapped (but not a cladding), the table may include |
---|
| 3113 | the thin layer's index of refraction. This allows the simulation of |
---|
| 3114 | boundary effects at the intersection between the medium and the |
---|
| 3115 | surface layer, as well as the Lambertian reflection at the far side |
---|
| 3116 | of the thin layer. This occurs within the process itself and does |
---|
| 3117 | not invoke the <literal>G4Navigator</literal>. Combinations of surface finish |
---|
| 3118 | properties, such as <emphasis>polished</emphasis> or |
---|
| 3119 | <emphasis>ground</emphasis> and <emphasis>front |
---|
| 3120 | painted</emphasis> or <emphasis>back painted</emphasis>, enumerate the different |
---|
| 3121 | situations which can be simulated. |
---|
| 3122 | </para> |
---|
| 3123 | |
---|
| 3124 | <para> |
---|
| 3125 | When a photon arrives at a medium boundary its behavior depends |
---|
| 3126 | on the nature of the two materials that join at that boundary. |
---|
| 3127 | Medium boundaries may be formed between two dielectric materials or |
---|
| 3128 | a dielectric and a metal. In the case of two dielectric materials, |
---|
| 3129 | the photon can undergo total internal reflection, refraction or |
---|
| 3130 | reflection, depending on the photon's wavelength, angle of |
---|
| 3131 | incidence, and the refractive indices on both sides of the |
---|
| 3132 | boundary. Furthermore, reflection and transmission probabilites are |
---|
| 3133 | sensitive to the state of linear polarization. In the case of an |
---|
| 3134 | interface between a dielectric and a metal, the photon can be |
---|
| 3135 | absorbed by the metal or reflected back into the dielectric. If the |
---|
| 3136 | photon is absorbed it can be detected according to the |
---|
| 3137 | photoelectron efficiency of the metal. |
---|
| 3138 | </para> |
---|
| 3139 | |
---|
| 3140 | <para> |
---|
| 3141 | As expressed in Maxwell's equations, Fresnel reflection and |
---|
| 3142 | refraction are intertwined through their relative probabilities of |
---|
| 3143 | occurrence. Therefore neither of these processes, nor total |
---|
| 3144 | internal reflection, are viewed as individual processes deserving |
---|
| 3145 | separate class implementation. Nonetheless, an attempt was made to |
---|
| 3146 | adhere to the abstraction of having independent processes by |
---|
| 3147 | splitting the code into different methods where practicable. |
---|
| 3148 | </para> |
---|
| 3149 | |
---|
| 3150 | <para> |
---|
| 3151 | One implementation of the <literal>G4OpBoundaryProcess</literal> class |
---|
| 3152 | employs the |
---|
| 3153 | <ulink url="http://geant4.slac.stanford.edu/UsersWorkshop/G4Lectures/Peter/moisan.ps"> |
---|
| 3154 | UNIFIED model</ulink> |
---|
| 3155 | [A. Levin and C. Moisan, A More Physical Approach |
---|
| 3156 | to Model the Surface Treatment of Scintillation Counters and its |
---|
| 3157 | Implementation into DETECT, TRIUMF Preprint TRI-PP-96-64, Oct. |
---|
| 3158 | 1996] of the DETECT program [G.F. Knoll, T.F. Knoll and T.M. |
---|
| 3159 | Henderson, Light Collection Scintillation Detector Composites for |
---|
| 3160 | Neutron Detection, IEEE Trans. Nucl. Sci., 35 (1988) 872.]. It |
---|
| 3161 | applies to dielectric-dielectric interfaces and tries to provide a |
---|
| 3162 | realistic simulation, which deals with all aspects of surface |
---|
| 3163 | finish and reflector coating. The surface may be assumed as smooth |
---|
| 3164 | and covered with a metallized coating representing a specular |
---|
| 3165 | reflector with given reflection coefficient, or painted with a |
---|
| 3166 | diffuse reflecting material where Lambertian reflection occurs. The |
---|
| 3167 | surfaces may or may not be in optical contact with another |
---|
| 3168 | component and most importantly, one may consider a surface to be |
---|
| 3169 | made up of micro-facets with normal vectors that follow given |
---|
| 3170 | distributions around the nominal normal for the volume at the |
---|
| 3171 | impact point. For very rough surfaces, it is possible for the |
---|
| 3172 | photon to inversely aim at the same surface again after reflection |
---|
| 3173 | of refraction and so multiple interactions with the boundary are |
---|
| 3174 | possible within the process itself and without the need for |
---|
| 3175 | relocation by <literal>G4Navigator</literal>. |
---|
| 3176 | </para> |
---|
| 3177 | |
---|
| 3178 | <para> |
---|
| 3179 | The UNIFIED model provides for a range of different reflection |
---|
| 3180 | mechanisms. The specular lobe constant represents the reflection |
---|
| 3181 | probability about the normal of a micro facet. The specular spike |
---|
| 3182 | constant, in turn, illustrates the probability of reflection about |
---|
| 3183 | the average surface normal. The diffuse lobe constant is for the |
---|
| 3184 | probability of internal Lambertian reflection, and finally the |
---|
| 3185 | back-scatter spike constant is for the case of several reflections |
---|
| 3186 | within a deep groove with the ultimate result of exact |
---|
| 3187 | back-scattering. The four probabilities must add up to one, with |
---|
| 3188 | the diffuse lobe constant being implicit. The reader may consult |
---|
| 3189 | the reference for a thorough description of the model. |
---|
| 3190 | |
---|
| 3191 | <example id="programlist_PhysProc_10"> |
---|
| 3192 | <title> |
---|
| 3193 | Dielectric-dielectric surface properties |
---|
| 3194 | defined via the <emphasis>G4OpticalSurface</emphasis>. |
---|
| 3195 | </title> |
---|
| 3196 | |
---|
| 3197 | <programlisting> |
---|
| 3198 | G4VPhysicalVolume* volume1; |
---|
| 3199 | G4VPhysicalVolume* volume2; |
---|
| 3200 | |
---|
| 3201 | G4OpticalSurface* OpSurface = new G4OpticalSurface("name"); |
---|
| 3202 | |
---|
| 3203 | G4LogicalBorderSurface* Surface = new |
---|
| 3204 | G4LogicalBorderSurface("name",volume1,volume2,OpSurface); |
---|
| 3205 | |
---|
| 3206 | G4double sigma_alpha = 0.1; |
---|
| 3207 | |
---|
| 3208 | OpSurface -> SetType(dielectric_dielectric); |
---|
| 3209 | OpSurface -> SetModel(unified); |
---|
| 3210 | OpSurface -> SetFinish(groundbackpainted); |
---|
| 3211 | OpSurface -> SetSigmaAlpha(sigma_alpha); |
---|
| 3212 | |
---|
| 3213 | const G4int NUM = 2; |
---|
| 3214 | |
---|
| 3215 | G4double pp[NUM] = {2.038*eV, 4.144*eV}; |
---|
| 3216 | G4double specularlobe[NUM] = {0.3, 0.3}; |
---|
| 3217 | G4double specularspike[NUM] = {0.2, 0.2}; |
---|
| 3218 | G4double backscatter[NUM] = {0.1, 0.1}; |
---|
| 3219 | G4double rindex[NUM] = {1.35, 1.40}; |
---|
| 3220 | G4double reflectivity[NUM] = {0.3, 0.5}; |
---|
| 3221 | G4double efficiency[NUM] = {0.8, 0.1}; |
---|
| 3222 | |
---|
| 3223 | G4MaterialPropertiesTable* SMPT = new G4MaterialPropertiesTable(); |
---|
| 3224 | |
---|
| 3225 | SMPT -> AddProperty("RINDEX",pp,rindex,NUM); |
---|
| 3226 | SMPT -> AddProperty("SPECULARLOBECONSTANT",pp,specularlobe,NUM); |
---|
| 3227 | SMPT -> AddProperty("SPECULARSPIKECONSTANT",pp,specularspike,NUM); |
---|
| 3228 | SMPT -> AddProperty("BACKSCATTERCONSTANT",pp,backscatter,NUM); |
---|
| 3229 | SMPT -> AddProperty("REFLECTIVITY",pp,reflectivity,NUM); |
---|
| 3230 | SMPT -> AddProperty("EFFICIENCY",pp,efficiency,NUM); |
---|
| 3231 | |
---|
| 3232 | OpSurface -> SetMaterialPropertiesTable(SMPT); |
---|
| 3233 | </programlisting> |
---|
| 3234 | </example> |
---|
| 3235 | </para> |
---|
| 3236 | |
---|
| 3237 | <para> |
---|
| 3238 | The original |
---|
| 3239 | <ulink url="http://wwwasdoc.web.cern.ch/wwwasdoc/geant_html3/node231.html"> |
---|
| 3240 | GEANT3.21 implementation</ulink> of this process is also available via |
---|
| 3241 | the GLISUR methods flag. [GEANT Detector Description and Simulation |
---|
| 3242 | Tool, Application Software Group, Computing and Networks Division, |
---|
| 3243 | CERN, PHYS260-6 tp 260-7.]. |
---|
| 3244 | |
---|
| 3245 | <example id="programlist_PhysProc_11"> |
---|
| 3246 | <title> |
---|
| 3247 | Dielectric metal surface properties defined via the |
---|
| 3248 | <emphasis>G4OpticalSurface</emphasis>. |
---|
| 3249 | </title> |
---|
| 3250 | |
---|
| 3251 | <programlisting> |
---|
| 3252 | G4LogicalVolume* volume_log; |
---|
| 3253 | |
---|
| 3254 | G4OpticalSurface* OpSurface = new G4OpticalSurface("name"); |
---|
| 3255 | |
---|
| 3256 | G4LogicalSkinSurface* Surface = new |
---|
| 3257 | G4LogicalSkinSurface("name",volume_log,OpSurface); |
---|
| 3258 | |
---|
| 3259 | OpSurface -> SetType(dielectric_metal); |
---|
| 3260 | OpSurface -> SetFinish(ground); |
---|
| 3261 | OpSurface -> SetModel(glisur); |
---|
| 3262 | |
---|
| 3263 | G4double polish = 0.8; |
---|
| 3264 | |
---|
| 3265 | G4MaterialPropertiesTable *OpSurfaceProperty = new G4MaterialPropertiesTable(); |
---|
| 3266 | |
---|
| 3267 | OpSurfaceProperty -> AddProperty("REFLECTIVITY",pp,reflectivity,NUM); |
---|
| 3268 | OpSurfaceProperty -> AddProperty("EFFICIENCY",pp,efficiency,NUM); |
---|
| 3269 | |
---|
| 3270 | OpSurface -> SetMaterialPropertiesTable(OpSurfaceProperty); |
---|
| 3271 | </programlisting> |
---|
| 3272 | </example> |
---|
| 3273 | </para> |
---|
| 3274 | |
---|
| 3275 | <para> |
---|
| 3276 | The reflectivity off a metal surface can also be calculated by way of a complex |
---|
| 3277 | index of refraction. Instead of storing the REFLECTIVITY directly, the user |
---|
| 3278 | stores the real part (REALRINDEX) and the imaginary part (IMAGINARYRINDEX) as |
---|
| 3279 | a function of photon energy separately in the G4MaterialPropertyTable. Geant4 |
---|
| 3280 | then |
---|
| 3281 | <ulink url="./AllResources/TrackingAndPhysics/physicsProcessOptical.src/GetReflectivity.pdf"> |
---|
| 3282 | calculates the reflectivity |
---|
| 3283 | </ulink> |
---|
| 3284 | depending on the incident angle, photon energy, degree of TE and TM |
---|
| 3285 | polarization, and this complex refractive index. |
---|
| 3286 | </para> |
---|
| 3287 | |
---|
| 3288 | <para> |
---|
| 3289 | The program defaults to the GLISUR model and <emphasis>polished</emphasis> |
---|
| 3290 | surface finish when no specific model and surface finish is |
---|
| 3291 | specified by the user. In the case of a dielectric-metal interface, |
---|
| 3292 | or when the GLISUR model is specified, the only surface finish |
---|
| 3293 | options available are <emphasis>polished</emphasis> or <emphasis>ground</emphasis>. For |
---|
| 3294 | dielectric-metal surfaces, the <literal>G4OpBoundaryProcess</literal> also |
---|
| 3295 | defaults to unit reflectivity and zero detection efficiency. In |
---|
| 3296 | cases where the user specifies the UNIFIED model, but does not |
---|
| 3297 | otherwise specify the model reflection probability constants, the |
---|
| 3298 | default becomes Lambertian reflection. |
---|
| 3299 | </para> |
---|
| 3300 | |
---|
[1211] | 3301 | <para> |
---|
| 3302 | Martin Janecek and Bill Moses (Lawrence Berkeley National Laboratory) |
---|
| 3303 | built an instrument for measuring the angular reflectivity distribution |
---|
| 3304 | inside of BGO crystals with common surface treatments and reflectors |
---|
| 3305 | applied. These results have been incorporate into the Geant4 code. A |
---|
| 3306 | third class of reflection type besides dielectric_metal and |
---|
| 3307 | dielectric_dielectric is added: dielectric_LUT. The distributions have |
---|
| 3308 | been converted to 21 look-up-tables (LUT); so far for 1 scintillator |
---|
| 3309 | material (BGO) x 3 surface treatments x 7 reflector materials. The |
---|
| 3310 | modified code allows the user to specify the surface treatment |
---|
| 3311 | (rough-cut, chemically etched, or mechanically polished), the attached |
---|
| 3312 | reflector (Lumirror, Teflon, ESR film, Tyvek, or TiO2 paint), and the |
---|
| 3313 | bonding type (air-coupled or glued). The glue used is MeltMount, and the |
---|
| 3314 | ESR film used is VM2000. Each LUT consists of measured angular |
---|
| 3315 | distributions with 4º by 5º resolution in theta and phi, respectively, |
---|
| 3316 | for incidence angles from 0º to 90º degrees, in 1º-steps. The code might |
---|
| 3317 | in the future be updated by adding more LUTs, for instance, for other |
---|
| 3318 | scintillating materials (such as LSO or NaI). To use these LUT the user |
---|
| 3319 | has to download them from |
---|
| 3320 | <ulink url="http://geant4.web.cern.ch/geant4/support/download.shtml"> |
---|
| 3321 | Geant4 Software Download</ulink> and set an environment variable, |
---|
| 3322 | <literal>G4REALSURFACEDATA</literal>, to the directory of |
---|
| 3323 | <literal>geant4/data/RealSurface1.0</literal>. For details see: |
---|
| 3324 | |
---|
| 3325 | <ulink url="./AllResources/TrackingAndPhysics/physicsProcessOptical.src/Janecek-TNS-00249-2009R1.pdf"> |
---|
| 3326 | M. Janecek, W. Moses IEEE Transactions on Nuclear Science |
---|
| 3327 | </ulink>. |
---|
| 3328 | </para> |
---|
| 3329 | |
---|
| 3330 | <para> |
---|
| 3331 | The enumeration G4OpticalSurfaceFinish has been extended to include |
---|
| 3332 | (what follows should be a 2 column table): |
---|
| 3333 | |
---|
| 3334 | <informalexample> |
---|
| 3335 | <programlisting> |
---|
| 3336 | polishedlumirrorair, // mechanically polished surface, with lumirror |
---|
| 3337 | polishedlumirrorglue, // mechanically polished surface, with lumirror & meltmount |
---|
| 3338 | polishedair, // mechanically polished surface |
---|
| 3339 | polishedteflonair, // mechanically polished surface, with teflon |
---|
| 3340 | polishedtioair, // mechanically polished surface, with tio paint |
---|
| 3341 | polishedtyvekair, // mechanically polished surface, with tyvek |
---|
| 3342 | polishedvm2000air, // mechanically polished surface, with esr film |
---|
| 3343 | polishedvm2000glue, // mechanically polished surface, with esr film & meltmount |
---|
| 3344 | etchedlumirrorair, // chemically etched surface, with lumirror |
---|
| 3345 | etchedlumirrorglue, // chemically etched surface, with lumirror & meltmount |
---|
| 3346 | etchedair, // chemically etched surface |
---|
| 3347 | etchedteflonair, // chemically etched surface, with teflon |
---|
| 3348 | etchedtioair, // chemically etched surface, with tio paint |
---|
| 3349 | etchedtyvekair, // chemically etched surface, with tyvek |
---|
| 3350 | etchedvm2000air, // chemically etched surface, with esr film |
---|
| 3351 | etchedvm2000glue, // chemically etched surface, with esr film & meltmount |
---|
| 3352 | groundlumirrorair, // rough-cut surface, with lumirror |
---|
| 3353 | groundlumirrorglue, // rough-cut surface, with lumirror & meltmount |
---|
| 3354 | groundair, // rough-cut surface |
---|
| 3355 | groundteflonair, // rough-cut surface, with teflon |
---|
| 3356 | groundtioair, // rough-cut surface, with tio paint |
---|
| 3357 | groundtyvekair, // rough-cut surface, with tyvek |
---|
| 3358 | groundvm2000air, // rough-cut surface, with esr film |
---|
| 3359 | groundvm2000glue // rough-cut surface, with esr film & meltmount |
---|
| 3360 | </programlisting> |
---|
| 3361 | </informalexample> |
---|
| 3362 | </para> |
---|
| 3363 | |
---|
| 3364 | <para> |
---|
| 3365 | To use a look-up-table, all the user needs to specify for an |
---|
| 3366 | <literal>G4OpticalSurface</literal> is: |
---|
| 3367 | <literal>SetType(dielectric_LUT), SetModel(LUT)</literal> and for example, |
---|
| 3368 | <literal>SetFinish(polishedtyvekair)</literal>. |
---|
| 3369 | </para> |
---|
| 3370 | |
---|
[904] | 3371 | </sect3> |
---|
| 3372 | </sect2> |
---|
| 3373 | |
---|
| 3374 | |
---|
| 3375 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 3376 | <sect2 id="sect.PhysProc.Param"> |
---|
| 3377 | <title> |
---|
| 3378 | Parameterization |
---|
| 3379 | </title> |
---|
| 3380 | |
---|
| 3381 | <para> |
---|
| 3382 | In this section we describe how to use the parameterization or |
---|
| 3383 | "fast simulation" facilities of GEANT4. Examples are provided in |
---|
| 3384 | the <emphasis role="bold">examples/novice/N05 directory</emphasis>. |
---|
| 3385 | </para> |
---|
| 3386 | |
---|
| 3387 | |
---|
| 3388 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 3389 | <sect3 id="sect.PhysProc.Param.Gene"> |
---|
| 3390 | <title> |
---|
| 3391 | Generalities: |
---|
| 3392 | </title> |
---|
| 3393 | |
---|
| 3394 | <para> |
---|
| 3395 | The Geant4 parameterization facilities allow you to shortcut the |
---|
| 3396 | detailed tracking in a given volume and for given particle types in |
---|
| 3397 | order for you to provide your own implementation of the physics and |
---|
| 3398 | of the detector response. |
---|
| 3399 | </para> |
---|
| 3400 | |
---|
| 3401 | <para> |
---|
| 3402 | Parameterisations are bound to a |
---|
| 3403 | <emphasis role="bold"><literal>G4Region</literal></emphasis> |
---|
| 3404 | object, which, in the case of fast simulation is also called an |
---|
| 3405 | <emphasis role="bold">envelope</emphasis>. Prior to release 8.0, |
---|
| 3406 | parameterisations were bound |
---|
| 3407 | to a <literal>G4LogicalVolume</literal>, the root of a volume hierarchy. |
---|
| 3408 | These root volumes are now attributes of the <literal>G4Region</literal>. |
---|
| 3409 | Envelopes often correspond to the volumes of sub-detectors: |
---|
| 3410 | electromagnetic calorimeters, tracking chambers, etc. With GEANT4 |
---|
| 3411 | it is also possible to define envelopes by overlaying a parallel or |
---|
| 3412 | "ghost" geometry as discussed in <xref linkend="sect.PhysProc.Param.Ghost" />. |
---|
| 3413 | </para> |
---|
| 3414 | |
---|
| 3415 | <para> |
---|
| 3416 | In GEANT4, parameterisations have three main features. You must |
---|
| 3417 | specify: |
---|
| 3418 | |
---|
| 3419 | <itemizedlist spacing="compact"> |
---|
| 3420 | <listitem><para> |
---|
| 3421 | the particle types for which your parameterisation is valid; |
---|
| 3422 | </para></listitem> |
---|
| 3423 | <listitem><para> |
---|
| 3424 | the dynamics conditions for which your parameterisation is |
---|
| 3425 | valid and must be triggered; |
---|
| 3426 | </para></listitem> |
---|
| 3427 | <listitem><para> |
---|
| 3428 | the parameterisation itself: where the primary will be killed |
---|
| 3429 | or moved, whether or not to create it or create secondaries, etc., |
---|
| 3430 | and where the detector response will be computed. |
---|
| 3431 | </para></listitem> |
---|
| 3432 | </itemizedlist> |
---|
| 3433 | </para> |
---|
| 3434 | |
---|
| 3435 | <para> |
---|
| 3436 | GEANT4 will message your parameterisation code for each step |
---|
| 3437 | starting in any root G4LogicalVolume (including daughters. |
---|
| 3438 | sub-daughters, etc. of this volume) of the <literal>G4Region</literal>. |
---|
| 3439 | It will proceed by first asking the available parameterisations for |
---|
| 3440 | the current particle type if one of them (and only one) wants to |
---|
| 3441 | issue a trigger. If so it will invoke its parameterisation. In this |
---|
| 3442 | case, the tracking |
---|
| 3443 | <emphasis role="bold"><emphasis>will not apply physics</emphasis></emphasis> |
---|
| 3444 | to the particle in the step. Instead, the UserSteppingAction will be |
---|
| 3445 | invoked. |
---|
| 3446 | </para> |
---|
| 3447 | |
---|
| 3448 | <para> |
---|
| 3449 | Parameterisations look like a "user stepping action" but are more |
---|
| 3450 | advanced because: |
---|
| 3451 | |
---|
| 3452 | <itemizedlist spacing="compact"> |
---|
| 3453 | <listitem><para> |
---|
| 3454 | parameterisation code is messaged only in the |
---|
| 3455 | <literal>G4Region</literal> to which it is bound; |
---|
| 3456 | </para></listitem> |
---|
| 3457 | <listitem><para> |
---|
| 3458 | parameterisation code is messaged anywhere in the |
---|
| 3459 | <literal>G4Region</literal>, that is, any volume in which the track is |
---|
| 3460 | located; |
---|
| 3461 | </para></listitem> |
---|
| 3462 | <listitem><para> |
---|
| 3463 | GEANT4 will provide information to your parameterisation code |
---|
| 3464 | about the current root volume of the <literal>G4Region</literal> |
---|
| 3465 | in which the track is travelling. |
---|
| 3466 | </para></listitem> |
---|
| 3467 | </itemizedlist> |
---|
| 3468 | </para> |
---|
| 3469 | |
---|
| 3470 | </sect3> |
---|
| 3471 | |
---|
| 3472 | |
---|
| 3473 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 3474 | <sect3 id="sect.PhysProc.Param.OvComp"> |
---|
| 3475 | <title> |
---|
| 3476 | Overview of Parameterisation Components |
---|
| 3477 | </title> |
---|
| 3478 | |
---|
| 3479 | <para> |
---|
| 3480 | The GEANT4 components which allow the implementation and control |
---|
| 3481 | of parameterisations are: |
---|
| 3482 | |
---|
| 3483 | <variablelist> |
---|
| 3484 | <varlistentry> |
---|
| 3485 | <term> |
---|
| 3486 | <literal><emphasis role="bold">G4VFastSimulationModel</emphasis></literal> |
---|
| 3487 | </term> |
---|
| 3488 | <listitem><para> |
---|
| 3489 | This is the abstract class for the implementation of parameterisations. |
---|
| 3490 | You must inherit from it to implement your concrete parameterisation model. |
---|
| 3491 | </para></listitem> |
---|
| 3492 | </varlistentry> |
---|
| 3493 | <varlistentry> |
---|
| 3494 | <term> |
---|
| 3495 | <literal><emphasis role="bold">G4FastSimulationManager</emphasis></literal> |
---|
| 3496 | </term> |
---|
| 3497 | <listitem><para> |
---|
| 3498 | The G4VFastSimulationModel objects are attached to the |
---|
| 3499 | <literal>G4Region</literal> through a G4FastSimulationManager. |
---|
| 3500 | This object will manage the list of models and will message them at |
---|
| 3501 | tracking time. |
---|
| 3502 | </para></listitem> |
---|
| 3503 | </varlistentry> |
---|
| 3504 | <varlistentry> |
---|
| 3505 | <term> |
---|
| 3506 | <literal><emphasis role="bold">G4Region/Envelope</emphasis></literal> |
---|
| 3507 | </term> |
---|
| 3508 | <listitem><para> |
---|
| 3509 | As mentioned before, an envelope in GEANT4 is a |
---|
| 3510 | <literal><emphasis role="bold">G4Region</emphasis></literal>. |
---|
| 3511 | The parameterisation is bound to the <literal>G4Region</literal> by |
---|
| 3512 | setting a <literal>G4FastSimulationManager</literal> pointer to it. |
---|
| 3513 | </para> |
---|
| 3514 | <para> |
---|
| 3515 | The figure below shows how the <literal>G4VFastSimulationModel</literal> |
---|
| 3516 | and <literal>G4FastSimulationManager</literal> objects are bound to the |
---|
| 3517 | <literal>G4Region</literal>. Then for all root G4LogicalVolume's held by |
---|
| 3518 | the G4Region, the fast simulation code is active. |
---|
| 3519 | |
---|
| 3520 | <mediaobject> |
---|
| 3521 | <imageobject role="fo"> |
---|
[921] | 3522 | <imagedata fileref="./AllResources/TrackingAndPhysics/physicsProcessPARAM.src/ComponentsWithRegion.jpg" |
---|
[904] | 3523 | format="JPG" contentwidth="7.0cm" align="center" /> |
---|
| 3524 | </imageobject> |
---|
| 3525 | <imageobject role="html"> |
---|
[921] | 3526 | <imagedata fileref="./AllResources/TrackingAndPhysics/physicsProcessPARAM.src/ComponentsWithRegion.jpg" |
---|
[904] | 3527 | format="JPG" align="center" /> |
---|
| 3528 | </imageobject> |
---|
| 3529 | <caption> |
---|
| 3530 | </caption> |
---|
| 3531 | </mediaobject> |
---|
| 3532 | |
---|
| 3533 | </para></listitem> |
---|
| 3534 | </varlistentry> |
---|
| 3535 | <varlistentry> |
---|
| 3536 | <term> |
---|
| 3537 | <literal><emphasis role="bold">G4FastSimulationManagerProcess</emphasis></literal> |
---|
| 3538 | </term> |
---|
| 3539 | <listitem><para> |
---|
| 3540 | This is a <literal>G4VProcess</literal>. It provides the interface |
---|
| 3541 | between the tracking and the parameterisation. It must be set in the |
---|
| 3542 | process list of the particles you want to parameterise. |
---|
| 3543 | </para></listitem> |
---|
| 3544 | </varlistentry> |
---|
| 3545 | <varlistentry> |
---|
| 3546 | <term> |
---|
| 3547 | <literal><emphasis role="bold">G4GlobalFastSimulationManager</emphasis></literal> |
---|
| 3548 | </term> |
---|
| 3549 | <listitem><para> |
---|
| 3550 | This a singleton class which provides the management of the |
---|
| 3551 | <literal>G4FastSimulationManager</literal> objects and some ghost |
---|
| 3552 | facilities. |
---|
| 3553 | </para></listitem> |
---|
| 3554 | </varlistentry> |
---|
| 3555 | </variablelist> |
---|
| 3556 | </para> |
---|
| 3557 | |
---|
| 3558 | </sect3> |
---|
| 3559 | |
---|
| 3560 | |
---|
| 3561 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 3562 | <sect3 id="sect.PhysProc.Param.FastSimModel"> |
---|
| 3563 | <title> |
---|
| 3564 | The <literal>G4VFastSimulationModel</literal> Abstract Class |
---|
| 3565 | </title> |
---|
| 3566 | |
---|
| 3567 | <!-- ******* Bridgehead ******* --> |
---|
| 3568 | <bridgehead renderas='sect4'> |
---|
| 3569 | Constructors: |
---|
| 3570 | </bridgehead> |
---|
| 3571 | |
---|
| 3572 | <para> |
---|
| 3573 | The <literal>G4VFastSimulationModel</literal> class has two constructors. |
---|
| 3574 | The second one allows you to get started quickly: |
---|
| 3575 | |
---|
| 3576 | <variablelist> |
---|
| 3577 | <varlistentry> |
---|
| 3578 | <term> |
---|
| 3579 | <emphasis role="bold"><literal>G4VFastSimulationModel( |
---|
| 3580 | const G4String& aName)</literal></emphasis>: |
---|
| 3581 | </term> |
---|
| 3582 | <listitem><para> |
---|
| 3583 | Here <literal>aName</literal> identifies the parameterisation model. |
---|
| 3584 | </para></listitem> |
---|
| 3585 | </varlistentry> |
---|
| 3586 | <varlistentry> |
---|
| 3587 | <term> |
---|
| 3588 | <emphasis role="bold"><literal>G4VFastSimulationModel(const G4String& |
---|
| 3589 | aName, G4Region*, G4bool IsUnique=false):</literal></emphasis> |
---|
| 3590 | </term> |
---|
| 3591 | <listitem><para> |
---|
| 3592 | In addition to the model name, this constructor accepts a G4Region pointer. |
---|
| 3593 | The needed G4FastSimulationManager object is constructed if necessary, |
---|
| 3594 | passing to it the G4Region pointer and the boolean value. If it |
---|
| 3595 | already exists, the model is simply added to this manager. Note |
---|
| 3596 | that the <emphasis>G4VFastSimulationModel object will not keep track of |
---|
| 3597 | the G4Region passed in the constructor</emphasis>. |
---|
| 3598 | The boolean argument is there for optimization purposes: if you |
---|
| 3599 | know that the G4Region has a unique root G4LogicalVolume, uniquely |
---|
| 3600 | placed, you can set the boolean value to "true". |
---|
| 3601 | </para></listitem> |
---|
| 3602 | </varlistentry> |
---|
| 3603 | </variablelist> |
---|
| 3604 | </para> |
---|
| 3605 | |
---|
| 3606 | <!-- ******* Bridgehead ******* --> |
---|
| 3607 | <bridgehead renderas='sect4'> |
---|
| 3608 | Virtual methods: |
---|
| 3609 | </bridgehead> |
---|
| 3610 | |
---|
| 3611 | <para> |
---|
| 3612 | The G4VFastSimulationModel has three pure virtual methods which |
---|
| 3613 | must be overriden in your concrete class: |
---|
| 3614 | |
---|
| 3615 | <variablelist> |
---|
| 3616 | <varlistentry> |
---|
| 3617 | <term> |
---|
| 3618 | <emphasis role="bold"><literal>G4VFastSimulationModel( |
---|
| 3619 | <emphasis>const G4String& aName</emphasis>):</literal></emphasis> |
---|
| 3620 | </term> |
---|
| 3621 | <listitem><para> |
---|
| 3622 | Here aName identifies the parameterisation model. |
---|
| 3623 | </para></listitem> |
---|
| 3624 | </varlistentry> |
---|
| 3625 | <varlistentry> |
---|
| 3626 | <term> |
---|
| 3627 | <emphasis role="bold"><literal>G4bool ModelTrigger( |
---|
| 3628 | <emphasis>const G4FastTrack&</emphasis>):</literal></emphasis> |
---|
| 3629 | </term> |
---|
| 3630 | <listitem><para> |
---|
| 3631 | You must return "true" when the dynamic conditions to trigger your |
---|
| 3632 | parameterisation are fulfilled. |
---|
| 3633 | G4FastTrack provides access to the current G4Track, gives simple |
---|
| 3634 | access to the current root G4LogicalVolume related features (its |
---|
| 3635 | G4VSolid, and G4AffineTransform references between the global and |
---|
| 3636 | the root G4LogicalVolume local coordinates systems) and simple |
---|
| 3637 | access to the position and momentum expressed in the root |
---|
| 3638 | G4LogicalVolume coordinate system. Using these quantities and the |
---|
| 3639 | G4VSolid methods, you can for example easily check how far you are |
---|
| 3640 | from the root G4LogicalVolume boundary. |
---|
| 3641 | </para></listitem> |
---|
| 3642 | </varlistentry> |
---|
| 3643 | <varlistentry> |
---|
| 3644 | <term> |
---|
| 3645 | <emphasis role="bold"><literal>G4bool IsApplicable( |
---|
| 3646 | <emphasis>const G4ParticleDefinition&</emphasis>):</literal></emphasis> |
---|
| 3647 | </term> |
---|
| 3648 | <listitem><para> |
---|
| 3649 | In your implementation, you must return "true" when your model is |
---|
| 3650 | applicable to the G4ParticleDefinition passed to this method. The |
---|
| 3651 | G4ParticleDefinition provides all intrinsic particle information |
---|
| 3652 | (mass, charge, spin, name ...). |
---|
| 3653 | </para> |
---|
| 3654 | <para> |
---|
| 3655 | If you want to implement a model which is valid only for certain |
---|
| 3656 | particle types, it is recommended for efficiency that you use the |
---|
| 3657 | static pointer of the corresponding particle classes. |
---|
| 3658 | </para> |
---|
| 3659 | <para> |
---|
| 3660 | As an example, in a model valid for <emphasis>gamma</emphasis>s only, |
---|
| 3661 | the IsApplicable() method should take the form: |
---|
| 3662 | |
---|
| 3663 | <informalexample> |
---|
| 3664 | <programlisting> |
---|
| 3665 | #include "G4Gamma.hh" |
---|
| 3666 | |
---|
| 3667 | G4bool MyGammaModel::IsApplicable(const G4ParticleDefinition& partDef) |
---|
| 3668 | { |
---|
| 3669 | return &partDef == G4Gamma::GammaDefinition(); |
---|
| 3670 | } |
---|
| 3671 | </programlisting> |
---|
| 3672 | </informalexample> |
---|
| 3673 | </para></listitem> |
---|
| 3674 | </varlistentry> |
---|
| 3675 | <varlistentry> |
---|
| 3676 | <term> |
---|
| 3677 | <emphasis role="bold"><literal>G4bool ModelTrigger( |
---|
| 3678 | <emphasis>const G4FastTrack&</emphasis>):</literal></emphasis> |
---|
| 3679 | </term> |
---|
| 3680 | <listitem><para> |
---|
| 3681 | You must return "true" when the dynamic conditions to trigger your |
---|
| 3682 | parameterisation are fulfilled. |
---|
| 3683 | The G4FastTrack provides access to the current G4Track, gives |
---|
| 3684 | simple access to envelope related features (G4LogicalVolume, |
---|
| 3685 | G4VSolid, and G4AffineTransform references between the global and |
---|
| 3686 | the envelope local coordinates systems) and simple access to the |
---|
| 3687 | position and momentum expressed in the envelope coordinate system. |
---|
| 3688 | Using these quantities and the G4VSolid methods, you can for |
---|
| 3689 | example easily check how far you are from the envelope boundary. |
---|
| 3690 | </para></listitem> |
---|
| 3691 | </varlistentry> |
---|
| 3692 | <varlistentry> |
---|
| 3693 | <term> |
---|
| 3694 | <emphasis role="bold"><literal>void DoIt( |
---|
| 3695 | <emphasis>const G4FastTrack&, G4FastStep&</emphasis>):</literal></emphasis> |
---|
| 3696 | </term> |
---|
| 3697 | <listitem><para> |
---|
| 3698 | The details of your parameterisation will be implemented in this method. |
---|
| 3699 | The G4FastTrack reference provides the input information, and the final |
---|
| 3700 | state of the particles after parameterisation must be returned |
---|
| 3701 | through the G4FastStep reference. Tracking for the final state |
---|
| 3702 | particles is requested after your parameterisation has been invoked. |
---|
| 3703 | </para></listitem> |
---|
| 3704 | </varlistentry> |
---|
| 3705 | </variablelist> |
---|
| 3706 | </para> |
---|
| 3707 | |
---|
| 3708 | </sect3> |
---|
| 3709 | |
---|
| 3710 | |
---|
| 3711 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 3712 | <sect3 id="sect.PhysProc.Param.FastSimMan"> |
---|
| 3713 | <title> |
---|
| 3714 | The <literal>G4FastSimulationManager</literal> Class: |
---|
| 3715 | </title> |
---|
| 3716 | |
---|
| 3717 | <para> |
---|
| 3718 | G4FastSimulationManager functionnalities regarding the use of ghost |
---|
| 3719 | volumes are explained in <xref linkend="sect.PhysProc.Param.Ghost" />. |
---|
| 3720 | </para> |
---|
| 3721 | |
---|
| 3722 | <!-- ******* Bridgehead ******* --> |
---|
| 3723 | <bridgehead renderas='sect4'> |
---|
| 3724 | Constructor: |
---|
| 3725 | </bridgehead> |
---|
| 3726 | |
---|
| 3727 | <para> |
---|
| 3728 | <variablelist> |
---|
| 3729 | <varlistentry> |
---|
| 3730 | <term> |
---|
| 3731 | <literal><emphasis role="bold">G4FastSimulationManager( |
---|
| 3732 | <emphasis>G4Region *anEnvelope, G4bool IsUnique=false</emphasis>): |
---|
| 3733 | </emphasis></literal> |
---|
| 3734 | </term> |
---|
| 3735 | <listitem><para> |
---|
| 3736 | This is the only constructor. You specify the G4Region by providing |
---|
| 3737 | its pointer. The G4FastSimulationManager object will bind itself |
---|
| 3738 | to this G4Region. If you know that this G4Region has a single root |
---|
| 3739 | G4LogicalVolume, placed only once, you can set the IsUnique boolean |
---|
| 3740 | to "true" to allow some optimization. |
---|
| 3741 | </para> |
---|
| 3742 | <para> |
---|
| 3743 | Note that if you choose to use the G4VFastSimulationModel(const |
---|
| 3744 | G4String&, G4Region*, G4bool) constructor for your model, the |
---|
| 3745 | G4FastSimulationManager will be constructed using the given |
---|
| 3746 | G4Region* and G4bool values of the model constructor. |
---|
| 3747 | </para></listitem> |
---|
| 3748 | </varlistentry> |
---|
| 3749 | </variablelist> |
---|
| 3750 | </para> |
---|
| 3751 | |
---|
| 3752 | <!-- ******* Bridgehead ******* --> |
---|
| 3753 | <bridgehead renderas='sect4'> |
---|
| 3754 | G4VFastSimulationModel object management: |
---|
| 3755 | </bridgehead> |
---|
| 3756 | |
---|
| 3757 | <para> |
---|
| 3758 | The following two methods provide the usual management |
---|
| 3759 | functions. |
---|
| 3760 | |
---|
| 3761 | <itemizedlist spacing="compact"> |
---|
| 3762 | <listitem><para> |
---|
| 3763 | <literal><emphasis role="bold">void AddFastSimulationModel( |
---|
| 3764 | G4VFastSimulationModel*)</emphasis></literal> |
---|
| 3765 | </para></listitem> |
---|
| 3766 | <listitem><para> |
---|
| 3767 | <literal><emphasis role="bold">RemoveFastSimulationModel( |
---|
| 3768 | G4VFastSimulationModel*)</emphasis></literal> |
---|
| 3769 | </para></listitem> |
---|
| 3770 | </itemizedlist> |
---|
| 3771 | </para> |
---|
| 3772 | |
---|
| 3773 | <!-- ******* Bridgehead ******* --> |
---|
| 3774 | <bridgehead renderas='sect4'> |
---|
| 3775 | Interface with the G4FastSimulationManagerProcess: |
---|
| 3776 | </bridgehead> |
---|
| 3777 | |
---|
| 3778 | <para> |
---|
| 3779 | This is described in the User's Guide for Toolkit Developers |
---|
| 3780 | ( |
---|
| 3781 | <!-- !!! xref linkend=""/ or ulink url="" --> |
---|
| 3782 | section 3.9.6 |
---|
| 3783 | <!-- !! /ulink (remove this tag for xref) --> |
---|
| 3784 | ) |
---|
| 3785 | </para> |
---|
| 3786 | |
---|
| 3787 | </sect3> |
---|
| 3788 | |
---|
| 3789 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 3790 | <sect3 id="sect.PhysProc.Param.FastSimManProc"> |
---|
| 3791 | <title> |
---|
| 3792 | The <literal>G4FastSimulationManagerProcess</literal> Class |
---|
| 3793 | </title> |
---|
| 3794 | |
---|
| 3795 | <para> |
---|
| 3796 | This G4VProcess serves as an interface between the tracking and the |
---|
| 3797 | parameterisation. At tracking time, it collaborates with the |
---|
| 3798 | G4FastSimulationManager of the current volume, if any, to allow the |
---|
| 3799 | models to trigger. If no manager exists or if no model issues a |
---|
| 3800 | trigger, the tracking goes on normally. |
---|
| 3801 | </para> |
---|
| 3802 | |
---|
| 3803 | <para> |
---|
| 3804 | <emphasis>In the present implementation, you must set this process in |
---|
| 3805 | the G4ProcessManager of the particles you parameterise to enable |
---|
| 3806 | your parameterisation.</emphasis> |
---|
| 3807 | </para> |
---|
| 3808 | |
---|
| 3809 | <para> |
---|
| 3810 | The processes ordering is: |
---|
| 3811 | |
---|
| 3812 | <informalexample> |
---|
| 3813 | <programlisting> |
---|
| 3814 | [n-3] ... |
---|
| 3815 | [n-2] Multiple Scattering |
---|
| 3816 | [n-1] G4FastSimulationManagerProcess |
---|
| 3817 | [ n ] G4Transportation |
---|
| 3818 | </programlisting> |
---|
| 3819 | </informalexample> |
---|
| 3820 | </para> |
---|
| 3821 | |
---|
| 3822 | <para> |
---|
| 3823 | This ordering is important if you use ghost geometries, since the |
---|
| 3824 | G4FastSimulationManagerProcess will provide navigation in the ghost |
---|
| 3825 | world to limit the step on ghost boundaries. |
---|
| 3826 | </para> |
---|
| 3827 | |
---|
| 3828 | <para> |
---|
| 3829 | The G4FastSimulationManager must be added to the process list of a |
---|
| 3830 | particle as a continuous and discrete process if you use ghost |
---|
| 3831 | geometries for this particle. You can add it as a discrete process |
---|
| 3832 | if you don't use ghosts. |
---|
| 3833 | </para> |
---|
| 3834 | |
---|
| 3835 | <para> |
---|
| 3836 | The following code registers the G4FastSimulationManagerProcess |
---|
| 3837 | with all the particles as a discrete and continuous process: |
---|
| 3838 | |
---|
| 3839 | <informalexample> |
---|
| 3840 | <programlisting> |
---|
| 3841 | void MyPhysicsList::addParameterisation() |
---|
| 3842 | { |
---|
| 3843 | G4FastSimulationManagerProcess* |
---|
| 3844 | theFastSimulationManagerProcess = new G4FastSimulationManagerProcess(); |
---|
| 3845 | theParticleIterator->reset(); |
---|
| 3846 | while( (*theParticleIterator)() ) |
---|
| 3847 | { |
---|
| 3848 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
| 3849 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
| 3850 | pmanager->AddProcess(theFastSimulationManagerProcess, -1, 0, 0); |
---|
| 3851 | } |
---|
| 3852 | } |
---|
| 3853 | </programlisting> |
---|
| 3854 | </informalexample> |
---|
| 3855 | </para> |
---|
| 3856 | |
---|
| 3857 | </sect3> |
---|
| 3858 | |
---|
| 3859 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 3860 | <sect3 id="sect.PhysProc.Param.FastSimManSing"> |
---|
| 3861 | <title> |
---|
| 3862 | The <literal>G4GlobalFastSimulationManager</literal> Singleton Class |
---|
| 3863 | </title> |
---|
| 3864 | |
---|
| 3865 | <para> |
---|
| 3866 | This class is a singleton which can be accessed as follows: |
---|
| 3867 | |
---|
| 3868 | <informalexample> |
---|
| 3869 | <programlisting> |
---|
| 3870 | #include "G4GlobalFastSimulationManager.hh" |
---|
| 3871 | ... |
---|
| 3872 | ... |
---|
| 3873 | G4GlobalFastSimulationManager* globalFSM; |
---|
| 3874 | globalFSM = G4GlobalFastSimulationManager::getGlobalFastSimulationManager(); |
---|
| 3875 | ... |
---|
| 3876 | ... |
---|
| 3877 | </programlisting> |
---|
| 3878 | </informalexample> |
---|
| 3879 | </para> |
---|
| 3880 | |
---|
| 3881 | <para> |
---|
| 3882 | Presently, you will mainly need to use the |
---|
| 3883 | GlobalFastSimulationManager if you use ghost geometries. |
---|
| 3884 | </para> |
---|
| 3885 | |
---|
| 3886 | </sect3> |
---|
| 3887 | |
---|
| 3888 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 3889 | <sect3 id="sect.PhysProc.Param.Ghost"> |
---|
| 3890 | <title> |
---|
| 3891 | Parameterisation Using Ghost Geometries |
---|
| 3892 | </title> |
---|
| 3893 | |
---|
| 3894 | <para> |
---|
| 3895 | In some cases, volumes of the tracking geometry do not allow |
---|
| 3896 | envelopes to be defined. This may be the case with a geometry |
---|
| 3897 | coming from a CAD system. Since such a geometry is flat, a parallel |
---|
| 3898 | geometry must be used to define the envelopes. |
---|
| 3899 | </para> |
---|
| 3900 | |
---|
| 3901 | <para> |
---|
| 3902 | Another interesting case involves defining an envelope which groups |
---|
| 3903 | the electromagnetic and hadronic calorimeters of a detector into |
---|
| 3904 | one volume. This may be useful when parameterizing the interaction |
---|
| 3905 | of charged pions. You will very likely not want electrons to see |
---|
| 3906 | this envelope, which means that ghost geometries have to be |
---|
| 3907 | organized by particle flavours. |
---|
| 3908 | </para> |
---|
| 3909 | |
---|
| 3910 | <para> |
---|
| 3911 | Using ghost geometries implies some more overhead in the |
---|
| 3912 | parameterisation mechanism for the particles sensitive to ghosts, |
---|
| 3913 | since navigation is provided in the ghost geometry by the |
---|
| 3914 | G4FastSimulationManagerProcess. Usually, however, only a few |
---|
| 3915 | volumes will be placed in this ghost world, so that the geometry |
---|
| 3916 | computations will remain rather cheap. |
---|
| 3917 | </para> |
---|
| 3918 | |
---|
| 3919 | <para> |
---|
| 3920 | In the existing implementation (temporary implementation with |
---|
| 3921 | G4Region but before parallel geometry implementation), you may only |
---|
| 3922 | consider ghost G4Regions with just one root G4LogicalVolume. The |
---|
| 3923 | G4GlobalFastSimulationManager provides the construction of the |
---|
| 3924 | ghost geometry by making first an empty "clone" of the world for |
---|
| 3925 | tracking provided by the construct() method of your |
---|
| 3926 | G4VUserDetectorConstruction concrete class. You provide the |
---|
| 3927 | placement of the G4Region root G4LogicalVolume relative to the |
---|
| 3928 | ghost world coordinates in the G4FastSimulationManager objects. A |
---|
| 3929 | ghost G4Region is recognized by the fact that its associated |
---|
| 3930 | G4FastSimulationManager retains a non-empty list of placements. |
---|
| 3931 | </para> |
---|
| 3932 | |
---|
| 3933 | <para> |
---|
| 3934 | The G4GlobalFastSimulationManager will then use both those |
---|
| 3935 | placements and the IsApplicable() methods of the models attached to |
---|
| 3936 | the G4FastSimulationManager objects to build the flavour-dependant |
---|
| 3937 | ghost geometries. |
---|
| 3938 | </para> |
---|
| 3939 | |
---|
| 3940 | <para> |
---|
| 3941 | Then at the beginning of the tracking of a particle, the |
---|
| 3942 | appropriate ghost world, if any, will be selected. |
---|
| 3943 | </para> |
---|
| 3944 | |
---|
| 3945 | <para> |
---|
| 3946 | The steps required to build one ghost G4Region are: |
---|
| 3947 | |
---|
| 3948 | <orderedlist spacing="compact"> |
---|
| 3949 | <listitem><para> |
---|
| 3950 | built the ghost G4Region : myGhostRegion; |
---|
| 3951 | </para></listitem> |
---|
| 3952 | <listitem><para> |
---|
| 3953 | build the root G4LogicalVolume: myGhostLogical, set it to |
---|
| 3954 | myGhostRegion; |
---|
| 3955 | </para></listitem> |
---|
| 3956 | <listitem><para> |
---|
| 3957 | build a G4FastSimulationManager object, myGhostFSManager, |
---|
| 3958 | giving myGhostRegion as argument of the constructor; |
---|
| 3959 | </para></listitem> |
---|
| 3960 | <listitem><para> |
---|
| 3961 | <para> |
---|
| 3962 | give to the G4FastSimulationManager the placement of the |
---|
| 3963 | myGhostLogical, by invoking for the G4FastSimulationManager method: |
---|
| 3964 | <informalexample> |
---|
| 3965 | <programlisting> |
---|
| 3966 | AddGhostPlacement(G4RotationMatrix*, const G4ThreeVector&); |
---|
| 3967 | </programlisting> |
---|
| 3968 | </informalexample> |
---|
| 3969 | or: |
---|
| 3970 | <informalexample> |
---|
| 3971 | <programlisting> |
---|
| 3972 | AddGhostPlacement(G4Transform3D*); |
---|
| 3973 | </programlisting> |
---|
| 3974 | </informalexample> |
---|
| 3975 | |
---|
| 3976 | where the rotation matrix and translation vector of the 3-D |
---|
| 3977 | transformation describe the placement relative to the ghost world |
---|
| 3978 | coordinates. |
---|
| 3979 | </para> |
---|
| 3980 | </para></listitem> |
---|
| 3981 | <listitem><para> |
---|
| 3982 | build your G4VFastSimulationModel objects and add them to the |
---|
| 3983 | myGhostFSManager. |
---|
| 3984 | <emphasis>The IsApplicable() methods of your models will be used by the |
---|
| 3985 | G4GlobalFastSimulationManager to build the ghost geometries |
---|
| 3986 | corresponding to a given particle type.</emphasis> |
---|
| 3987 | </para></listitem> |
---|
| 3988 | <listitem><para> |
---|
| 3989 | <para> |
---|
| 3990 | Invoke the G4GlobalFastSimulationManager method: |
---|
| 3991 | |
---|
| 3992 | <informalexample> |
---|
| 3993 | <programlisting> |
---|
| 3994 | G4GlobalFastSimulationManager::getGlobalFastSimulationManager()-> |
---|
| 3995 | |
---|
| 3996 | CloseFastSimulation(); |
---|
| 3997 | </programlisting> |
---|
| 3998 | </informalexample> |
---|
| 3999 | </para> |
---|
| 4000 | </para></listitem> |
---|
| 4001 | </orderedlist> |
---|
| 4002 | </para> |
---|
| 4003 | |
---|
| 4004 | <para> |
---|
| 4005 | This last call will cause the G4GlobalFastSimulationManager to |
---|
| 4006 | build the flavour-dependent ghost geometries. This call must be |
---|
| 4007 | done before the RunManager closes the geometry. (It is foreseen |
---|
| 4008 | that the run manager in the future will invoke the |
---|
| 4009 | CloseFastSimulation() to synchronize properly with the closing of |
---|
| 4010 | the geometry). |
---|
| 4011 | </para> |
---|
| 4012 | |
---|
| 4013 | <para> |
---|
| 4014 | Visualization facilities are provided for ghosts geometries. After |
---|
| 4015 | the CloseFastSimulation() invocation, it is possible to ask for the |
---|
| 4016 | drawing of ghosts in an interactive session. The basic commands |
---|
| 4017 | are: |
---|
| 4018 | |
---|
| 4019 | <itemizedlist spacing="compact"> |
---|
| 4020 | <listitem><para> |
---|
| 4021 | <para> |
---|
| 4022 | /vis/draw/Ghosts particle_name |
---|
| 4023 | </para> |
---|
| 4024 | <para> |
---|
| 4025 | which makes the drawing of the ghost geometry associated with the |
---|
| 4026 | particle specified by name in the command line. |
---|
| 4027 | </para> |
---|
| 4028 | </para></listitem> |
---|
| 4029 | <listitem><para> |
---|
| 4030 | /vis/draw/Ghosts |
---|
| 4031 | <para> |
---|
| 4032 | which draws all the ghost geometries. |
---|
| 4033 | </para> |
---|
| 4034 | </para></listitem> |
---|
| 4035 | </itemizedlist> |
---|
| 4036 | </para> |
---|
| 4037 | |
---|
| 4038 | </sect3> |
---|
| 4039 | |
---|
| 4040 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 4041 | <sect3 id="sect.PhysProc.Param.GFlash"> |
---|
| 4042 | <title> |
---|
| 4043 | Gflash Parameterization |
---|
| 4044 | </title> |
---|
| 4045 | |
---|
| 4046 | <para> |
---|
| 4047 | This section describes how to use the Gflash library. Gflash is a |
---|
| 4048 | concrete parameterization which is based on the equations and |
---|
| 4049 | parameters of the original Gflash package from H1(hep-ex/0001020, |
---|
| 4050 | Grindhammer & Peters, see physics manual) and uses the "fast |
---|
| 4051 | simulation" facilities of GEANT4 described above. Briefly, whenever |
---|
| 4052 | a e-/e+ particle enters the calorimeter, it is parameterized if it |
---|
| 4053 | has a minimum energy and the shower is expected to be contained in |
---|
| 4054 | the calorimeter (or " parameterization envelope"). If this is |
---|
| 4055 | fulfilled the particle is killed, as well as all secondaries, and |
---|
| 4056 | the energy is deposited according to the Gflash equations. An |
---|
| 4057 | example, provided in |
---|
| 4058 | <emphasis role="bold">examples/extended/parametrisation/gflash/</emphasis>, |
---|
| 4059 | shows how to interface Gflash to your application. The simulation time is |
---|
| 4060 | measured, so the user can immediately see the speed increase |
---|
| 4061 | resulting from the use of Gflash. |
---|
| 4062 | </para> |
---|
| 4063 | |
---|
| 4064 | </sect3> |
---|
| 4065 | |
---|
| 4066 | <!-- ******************* Section (Level#3) ****************** --> |
---|
| 4067 | <sect3 id="sect.PhysProc.Param.UsingGFlash"> |
---|
| 4068 | <title> |
---|
| 4069 | Using the Gflash Parameterisation |
---|
| 4070 | </title> |
---|
| 4071 | |
---|
| 4072 | <para> |
---|
| 4073 | To use Gflash "out of the box" the following steps are necessary: |
---|
| 4074 | |
---|
| 4075 | <itemizedlist spacing="compact"> |
---|
| 4076 | <listitem><para> |
---|
| 4077 | The user must add the fast simulation process to his process |
---|
| 4078 | manager: |
---|
| 4079 | |
---|
| 4080 | <informalexample> |
---|
| 4081 | <programlisting> |
---|
| 4082 | void MyPhysicsList::addParameterisation() |
---|
| 4083 | { |
---|
| 4084 | G4FastSimulationManagerProcess* |
---|
| 4085 | theFastSimulationManagerProcess = new G4FastSimulationManagerProcess(); |
---|
| 4086 | theParticleIterator->reset(); |
---|
| 4087 | while( (*theParticleIterator)() ) |
---|
| 4088 | { |
---|
| 4089 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
| 4090 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
| 4091 | pmanager->AddProcess(theFastSimulationManagerProcess, -1, 0, 0); |
---|
| 4092 | } |
---|
| 4093 | } |
---|
| 4094 | </programlisting> |
---|
| 4095 | </informalexample> |
---|
| 4096 | </para></listitem> |
---|
| 4097 | <listitem><para> |
---|
| 4098 | <para> |
---|
| 4099 | The envelope in which the parameterization should be performed |
---|
| 4100 | must be specified (below: G4Region m_calo_region) and the |
---|
| 4101 | GFlashShowerModel must be assigned to this region. Furthermore, the |
---|
| 4102 | classes GFlashParticleBounds (which provides thresholds for the |
---|
| 4103 | parameterization like minimal energy etc.), GflashHitMaker(a helper |
---|
| 4104 | class to generate hits in the sensitive detector) and |
---|
| 4105 | GFlashHomoShowerParamterisation (which does the computations) must |
---|
| 4106 | be constructed (by the user at the moment) and assigned to the |
---|
| 4107 | GFlashShowerModel. Please note that at the moment only homogeneous |
---|
| 4108 | calorimeters are supported. |
---|
| 4109 | </para> |
---|
| 4110 | <para> |
---|
| 4111 | <informalexample> |
---|
| 4112 | <programlisting> |
---|
| 4113 | m_theFastShowerModel = new GFlashShowerModel("fastShowerModel",m_calo_region); |
---|
| 4114 | m_theParametrisation = new GFlashHomoShowerParamterisation(matManager->getMaterial(mat)); |
---|
| 4115 | m_theParticleBounds = new GFlashParticleBounds(); |
---|
| 4116 | m_theHMaker = new GFlashHitMaker(); |
---|
| 4117 | m_theFastShowerModel->SetParametrisation(*m_theParametrisation); |
---|
| 4118 | m_theFastShowerModel->SetParticleBounds(*m_theParticleBounds) ; |
---|
| 4119 | m_theFastShowerModel->SetHitMaker(*m_theHMaker); |
---|
| 4120 | </programlisting> |
---|
| 4121 | </informalexample> |
---|
| 4122 | </para> |
---|
| 4123 | <para> |
---|
| 4124 | The user must also set the material of the calorimeter, since the |
---|
| 4125 | computation depends on the material. |
---|
| 4126 | </para> |
---|
| 4127 | </para></listitem> |
---|
| 4128 | <listitem><para> |
---|
| 4129 | <para> |
---|
| 4130 | It is mandatory to use G4VGFlashSensitiveDetector as |
---|
| 4131 | (additional) base class for the sensitive detector. |
---|
| 4132 | </para> |
---|
| 4133 | <para> |
---|
| 4134 | <informalexample> |
---|
| 4135 | <programlisting> |
---|
| 4136 | class ExGflashSensitiveDetector: public G4VSensitiveDetector ,public G4VGFlashSensitiveDetector |
---|
| 4137 | </programlisting> |
---|
| 4138 | </informalexample> |
---|
| 4139 | </para> |
---|
| 4140 | <para> |
---|
| 4141 | Here it is necessary to implement a separate interface, where the |
---|
| 4142 | GFlash spots are processed. |
---|
| 4143 | </para> |
---|
| 4144 | <para> |
---|
| 4145 | <informalexample> |
---|
| 4146 | <programlisting> |
---|
| 4147 | (ProcessHits(G4GFlashSpot*aSpot ,G4TouchableHistory* ROhist)) |
---|
| 4148 | </programlisting> |
---|
| 4149 | </informalexample> |
---|
| 4150 | </para> |
---|
| 4151 | <para> |
---|
| 4152 | A separate interface is used, because the Gflash spots naturally |
---|
| 4153 | contain less information than the full simulation. |
---|
| 4154 | </para> |
---|
| 4155 | </para></listitem> |
---|
| 4156 | </itemizedlist> |
---|
| 4157 | </para> |
---|
| 4158 | |
---|
| 4159 | <para> |
---|
| 4160 | Since the parameters in the Gflash package are taken from fits to |
---|
| 4161 | full simulations with Geant3, some retuning might be necessary for |
---|
| 4162 | good agreement with Geant4 showers. For experiment-specific |
---|
| 4163 | geometries some retuning might be necessary anyway. The tuning is |
---|
| 4164 | quite complicated since there are many parameters (some correlated) |
---|
| 4165 | and cannot be described here (see again hep-ex/0001020). For brave |
---|
| 4166 | users the Gflash framework already forsees the possibility of |
---|
| 4167 | passing a class with the (users) |
---|
| 4168 | parameters,<emphasis role="bold">GVFlashHomoShowerTuning</emphasis>, |
---|
| 4169 | to the GFlashHomoShowerParamterisation constructor. |
---|
| 4170 | The default parameters are the original Gflash parameters: |
---|
| 4171 | |
---|
| 4172 | <informalexample> |
---|
| 4173 | <programlisting> |
---|
| 4174 | GFlashHomoShowerParameterisation(G4Material * aMat, GVFlashHomoShowerTuning * aPar = 0); |
---|
| 4175 | </programlisting> |
---|
| 4176 | </informalexample> |
---|
| 4177 | </para> |
---|
| 4178 | |
---|
| 4179 | <para> |
---|
| 4180 | Now there is also a preliminary implemenation of a parameterization |
---|
| 4181 | for sampling calorimeters. |
---|
| 4182 | </para> |
---|
| 4183 | |
---|
| 4184 | <para> |
---|
| 4185 | The user must specify the active and passive material, as well as |
---|
| 4186 | the thickness of the active and passive layer. |
---|
| 4187 | </para> |
---|
| 4188 | |
---|
| 4189 | <para> |
---|
| 4190 | The sampling structure of the calorimeter is taken into account by |
---|
| 4191 | using an "effective medium" to compute the shower shape. |
---|
| 4192 | </para> |
---|
| 4193 | |
---|
| 4194 | <para> |
---|
| 4195 | All material properties needed are calculated automatically. If |
---|
| 4196 | tuning is required, the user can pass his own parameter set in |
---|
| 4197 | the class |
---|
| 4198 | <emphasis role="bold">GFlashSamplingShowerTuning</emphasis>. |
---|
| 4199 | Here the user can also set his calorimeter resolution. |
---|
| 4200 | </para> |
---|
| 4201 | |
---|
| 4202 | <para> |
---|
| 4203 | All in all the constructor looks the following: |
---|
| 4204 | |
---|
| 4205 | <informalexample> |
---|
| 4206 | <programlisting> |
---|
| 4207 | GFlashSamplingShowerParamterisation(G4Material * Mat1, G4Material * Mat2,G4double d1,G4double d2, |
---|
| 4208 | GVFlashSamplingShowerTuning * aPar = 0); |
---|
| 4209 | </programlisting> |
---|
| 4210 | </informalexample> |
---|
| 4211 | </para> |
---|
| 4212 | |
---|
| 4213 | <para> |
---|
| 4214 | An implementation of some tools that should help the user to tune |
---|
| 4215 | the parameterization is forseen. |
---|
| 4216 | </para> |
---|
| 4217 | |
---|
| 4218 | </sect3> |
---|
| 4219 | </sect2> |
---|
| 4220 | |
---|
| 4221 | |
---|
| 4222 | <!-- ******************* Section (Level#2) ****************** --> |
---|
| 4223 | <sect2 id="sect.PhysProc.Trans"> |
---|
| 4224 | <title> |
---|
| 4225 | Transportation Process |
---|
| 4226 | </title> |
---|
| 4227 | |
---|
| 4228 | <para> |
---|
| 4229 | To be delivered by J. Apostolakis (<email>John.Apostolakis@cern.ch</email>). |
---|
| 4230 | </para> |
---|
| 4231 | |
---|
| 4232 | |
---|
| 4233 | </sect2> |
---|
| 4234 | </sect1> |
---|