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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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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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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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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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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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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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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439 | Multiple scattering (class name <emphasis>G4MuMultipleScattering</emphasis>) |
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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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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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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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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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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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463 | Multiple scattering (class name <emphasis>G4hMultipleScattering</emphasis>) |
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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 | Alternative process for simulation of single Coulomb scattering |
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480 | of all charged particles (class name <emphasis>G4CoulombScattering</emphasis>) |
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481 | </para></listitem> |
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482 | <listitem><para> |
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483 | Alternative process for simulation of single Coulomb scattering |
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484 | of ions (class name <emphasis>G4ScreenedNuclearRecoil</emphasis>) |
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485 | </para></listitem> |
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486 | </itemizedlist> |
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487 | </para></listitem> |
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488 | <listitem><para> |
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489 | Processes for simulation of polarized electron and gamma beams |
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490 | <itemizedlist spacing="compact"> |
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491 | <listitem><para> |
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492 | Compton scattering of circularly polarized gamma beam on |
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493 | polarized target (class name <emphasis>G4PolarizedCompton</emphasis>) |
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494 | </para></listitem> |
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495 | <listitem><para> |
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496 | Pair production induced by circularly polarized gamma beam |
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497 | (class name <emphasis>G4PolarizedGammaConversion</emphasis>) |
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498 | </para></listitem> |
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499 | <listitem><para> |
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500 | Photo-electric effect induced by circularly polarized gamma beam |
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501 | (class name <emphasis>G4PolarizedPhotoElectricEffect</emphasis>) |
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502 | </para></listitem> |
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503 | <listitem><para> |
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504 | Bremsstrahlung of polarized electrons and positrons |
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505 | (class name <emphasis>G4ePolarizedBremsstrahlung</emphasis>) |
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506 | </para></listitem> |
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507 | <listitem><para> |
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508 | Ionisation of polarized electron and positron beam |
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509 | (class name <emphasis>G4ePolarizedIonisation</emphasis>) |
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510 | </para></listitem> |
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511 | <listitem><para> |
---|
512 | Annihilation of polarized positrons |
---|
513 | (class name <emphasis>G4eplusPolarizedAnnihilation</emphasis>) |
---|
514 | </para></listitem> |
---|
515 | </itemizedlist> |
---|
516 | </para></listitem> |
---|
517 | <listitem><para> |
---|
518 | Processes for simulation of X-rays and optical protons production by charged particles |
---|
519 | <itemizedlist spacing="compact"> |
---|
520 | <listitem><para> |
---|
521 | Synchrotron radiation (class name <emphasis>G4SynchrotronRadiation</emphasis>) |
---|
522 | </para></listitem> |
---|
523 | <listitem><para> |
---|
524 | Transition radiation |
---|
525 | (class name <emphasis>G4TransitionRadiation</emphasis>) |
---|
526 | </para></listitem> |
---|
527 | <listitem><para> |
---|
528 | Cerenkov radiation |
---|
529 | (class name <emphasis>G4Cerenkov</emphasis>) |
---|
530 | </para></listitem> |
---|
531 | <listitem><para> |
---|
532 | Scintillations |
---|
533 | (class name <emphasis>G4Scintillation</emphasis>) |
---|
534 | </para></listitem> |
---|
535 | </itemizedlist> |
---|
536 | </para></listitem> |
---|
537 | <listitem><para> |
---|
538 | The processes described above use physics model classes, which |
---|
539 | may be combined according to particle energy. It is possible to |
---|
540 | change the energy range over which different models are valid, and |
---|
541 | to apply other models specific to particle type, energy range, and |
---|
542 | G4Region. The following alternative models are available: |
---|
543 | <itemizedlist spacing="compact"> |
---|
544 | <listitem><para> |
---|
545 | Ionisation in thin absorbers (class name <emphasis>G4PAIModel</emphasis>) |
---|
546 | </para></listitem> |
---|
547 | </itemizedlist> |
---|
548 | </para></listitem> |
---|
549 | </itemizedlist> |
---|
550 | </para> |
---|
551 | |
---|
552 | <para> |
---|
553 | It is recommended to use physics constructor classes provided |
---|
554 | with rederence physics lists ($G4INSTALL/source/physics_lists/builders): |
---|
555 | <itemizedlist spacing="compact"> |
---|
556 | <listitem><para> |
---|
557 | default EM physics (class name <emphasis>G4EmStandardPhysics</emphasis>) |
---|
558 | </para></listitem> |
---|
559 | <listitem><para> |
---|
560 | optional EM physics providing fast but less acurate electron transport due to |
---|
561 | "Simple" method of step limitation by multiple scattering, reduced |
---|
562 | step limitation by ionisation process and enabled "ApplyCuts" option |
---|
563 | (class name <emphasis>G4EmStandardPhysics_option1</emphasis>) |
---|
564 | </para></listitem> |
---|
565 | <listitem><para> |
---|
566 | Experimental EM physics with enabled "ApplyCuts" option, <emphasis>G4WentzelVIModel</emphasis> |
---|
567 | for muon multiple scattering |
---|
568 | (class name <emphasis>G4EmStandardPhysics_option2</emphasis>) |
---|
569 | </para></listitem> |
---|
570 | <listitem><para> |
---|
571 | EM physics for simulation with high accuracy due to "UseDistanceToBoundary" multiple |
---|
572 | scattering step limitation, reduced <emphasis>finalRange</emphasis> parameter of stepping function |
---|
573 | optimized per particle type, <emphasis>G4WentzelVIModel</emphasis> |
---|
574 | for muon multiple scattering and <emphasis>G4IonParameterisedLossModel</emphasis> for ion ionisation |
---|
575 | (class name <emphasis>G4EmStandardPhysics_option3</emphasis>) |
---|
576 | </para></listitem> |
---|
577 | <listitem><para> |
---|
578 | Combined Standard and Low-energy EM physics constructors based on the Option3 constructor; |
---|
579 | low-energy models are applied below 1 GeV: |
---|
580 | <itemizedlist spacing="compact"> |
---|
581 | <listitem><para> |
---|
582 | Models based on Livermore data bases for electrons and gamma (<emphasis>G4EmLivermorePhysics</emphasis>); |
---|
583 | </para></listitem> |
---|
584 | <listitem><para> |
---|
585 | Polarized models based on Livermore data bases for electrons and gamma (<emphasis>G4EmLivermorePolarizedPhysics</emphasis>); |
---|
586 | </para></listitem> |
---|
587 | <listitem><para> |
---|
588 | Penelope models for electrons, positrons and gamma (<emphasis>G4EmPenelopePhysics</emphasis>); |
---|
589 | </para></listitem> |
---|
590 | <listitem><para> |
---|
591 | Low-energy DNA physics (<emphasis>G4EmDNAPhysics</emphasis>). |
---|
592 | </para></listitem> |
---|
593 | </itemizedlist> |
---|
594 | </para></listitem> </itemizedlist> |
---|
595 | Examples of the registration of these physics constructor and |
---|
596 | construction of alternative combinations of options are shown |
---|
597 | in novice, extended and advanced examples ($G4INSTALL/examples/extended/electromagnetic and $G4INSTALL/examples/advanced). |
---|
598 | Examples illustrating the use |
---|
599 | of electromagnetic processes are available as part of the Geant4 |
---|
600 | <ulink url="http://geant4.web.cern.ch/geant4/support/download.shtml"> |
---|
601 | release</ulink>. |
---|
602 | </para> |
---|
603 | |
---|
604 | <para> |
---|
605 | <emphasis role="bold">Options</emphasis> are available for steering of |
---|
606 | electromagnetic processes. These options may be invoked either by |
---|
607 | UI commands or by the interface class G4EmProcessOptions. This |
---|
608 | class has the following public methods: |
---|
609 | |
---|
610 | <itemizedlist spacing="compact"> |
---|
611 | <listitem><para> |
---|
612 | SetLossFluctuations(G4bool) |
---|
613 | </para></listitem> |
---|
614 | <listitem><para> |
---|
615 | SetSubCutoff(G4bool, const G4Region* r=0) |
---|
616 | </para></listitem> |
---|
617 | <listitem><para> |
---|
618 | SetIntegral(G4bool) |
---|
619 | </para></listitem> |
---|
620 | <listitem><para> |
---|
621 | SetMinSubRange(G4double) |
---|
622 | </para></listitem> |
---|
623 | <listitem><para> |
---|
624 | SetMinEnergy(G4double) |
---|
625 | </para></listitem> |
---|
626 | <listitem><para> |
---|
627 | SetMaxEnergy(G4double) |
---|
628 | </para></listitem> |
---|
629 | <listitem><para> |
---|
630 | SetMaxEnergyForCSDARange(G4double) |
---|
631 | </para></listitem> |
---|
632 | <listitem><para> |
---|
633 | SetMaxEnergyForMuons(G4double) |
---|
634 | </para></listitem> |
---|
635 | <listitem><para> |
---|
636 | SetDEDXBinning(G4int) |
---|
637 | </para></listitem> |
---|
638 | <listitem><para> |
---|
639 | SetDEDXBinningForCSDARange(G4int) |
---|
640 | </para></listitem> |
---|
641 | <listitem><para> |
---|
642 | SetLambdaBinning(G4int) |
---|
643 | </para></listitem> |
---|
644 | <listitem><para> |
---|
645 | SetStepFunction(G4double, G4double) |
---|
646 | </para></listitem> |
---|
647 | <listitem><para> |
---|
648 | SetRandomStep(G4bool) |
---|
649 | </para></listitem> |
---|
650 | <listitem><para> |
---|
651 | SetApplyCuts(G4bool) |
---|
652 | </para></listitem> |
---|
653 | <listitem><para> |
---|
654 | SetSpline(G4bool) |
---|
655 | </para></listitem> |
---|
656 | <listitem><para> |
---|
657 | SetBuildCSDARange(G4bool) |
---|
658 | </para></listitem> |
---|
659 | <listitem><para> |
---|
660 | SetVerbose(G4int, const G4String name= "all") |
---|
661 | </para></listitem> |
---|
662 | <listitem><para> |
---|
663 | SetLambdaFactor(G4double) |
---|
664 | </para></listitem> |
---|
665 | <listitem><para> |
---|
666 | SetLinearLossLimit(G4double) |
---|
667 | </para></listitem> |
---|
668 | <listitem><para> |
---|
669 | ActivateDeexcitation(G4bool val, const G4Region* r = 0) |
---|
670 | </para></listitem> |
---|
671 | <listitem><para> |
---|
672 | SetMscStepLimitation(G4MscStepLimitType val) |
---|
673 | </para></listitem> |
---|
674 | <listitem><para> |
---|
675 | SetMscLateralDisplacement(G4bool val) |
---|
676 | </para></listitem> |
---|
677 | <listitem><para> |
---|
678 | SetSkin(G4double) |
---|
679 | </para></listitem> |
---|
680 | <listitem><para> |
---|
681 | SetMscRangeFactor(G4double) |
---|
682 | </para></listitem> |
---|
683 | <listitem><para> |
---|
684 | SetMscGeomFactor(G4double) |
---|
685 | </para></listitem> |
---|
686 | <listitem><para> |
---|
687 | SetLPMFlag(G4bool) |
---|
688 | </para></listitem> |
---|
689 | <listitem><para> |
---|
690 | SetBremsstrahlungTh(G4double) |
---|
691 | </para></listitem> |
---|
692 | <listitem><para> |
---|
693 | SetPolarAngleLimit(G4double) |
---|
694 | </para></listitem> |
---|
695 | <listitem><para> |
---|
696 | SetFactorForAngleLimit(G4double) |
---|
697 | </para></listitem> |
---|
698 | </itemizedlist> |
---|
699 | </para> |
---|
700 | |
---|
701 | <para> |
---|
702 | The corresponding UI command can be accessed in the UI subdirectory |
---|
703 | "/process/eLoss". The following types of step limitation by multiple scattering |
---|
704 | are available: |
---|
705 | |
---|
706 | <itemizedlist spacing="compact"> |
---|
707 | <listitem><para> |
---|
708 | fSimple - simplified step limitation as in g4 7.1 version (used in QGSP_BERT_EMV Physics List) |
---|
709 | </para></listitem> |
---|
710 | <listitem><para> |
---|
711 | fUseSafety - default |
---|
712 | </para></listitem> |
---|
713 | <listitem><para> |
---|
714 | fUseDistanceToBoundary - advance method of step limitation used in EM examples, |
---|
715 | required parameter <emphasis>skin > 0</emphasis>, should be used for |
---|
716 | setup without magnetic field |
---|
717 | </para></listitem> |
---|
718 | </itemizedlist> |
---|
719 | </para> |
---|
720 | |
---|
721 | <para> |
---|
722 | <emphasis role="bold">G4EmCalculator</emphasis> is a class which provides |
---|
723 | access to cross sections and stopping powers. This class can be used |
---|
724 | anywhere in the user code provided the physics list has already been |
---|
725 | initialised (G4State_Idle). G4EmCalculator has "Get" methods which |
---|
726 | can be applied to materials for which physics tables are already |
---|
727 | built, and "Compute" methods which can be applied to any material |
---|
728 | defined in the application or existing in the Geant4 internal |
---|
729 | database. The public methods of this class are: |
---|
730 | |
---|
731 | <itemizedlist spacing="compact"> |
---|
732 | <listitem><para> |
---|
733 | GetDEDX(kinEnergy,particle,material,G4Region region=0) |
---|
734 | </para></listitem> |
---|
735 | <listitem><para> |
---|
736 | GetRangeFromRestrictedDEDX(kinEnergy,particle,material,G4Region* region=0) |
---|
737 | </para></listitem> |
---|
738 | <listitem><para> |
---|
739 | GetCSDARange(kinEnergy,particle,material,G4Region* region=0) |
---|
740 | </para></listitem> |
---|
741 | <listitem><para> |
---|
742 | GetRange(kinEnergy,particle,material,G4Region* region=0) |
---|
743 | </para></listitem> |
---|
744 | <listitem><para> |
---|
745 | GetKinEnergy(range,particle,material,G4Region* region=0) |
---|
746 | </para></listitem> |
---|
747 | <listitem><para> |
---|
748 | GetCrosSectionPerVolume(kinEnergy,particle,material,G4Region* region=0) |
---|
749 | </para></listitem> |
---|
750 | <listitem><para> |
---|
751 | GetMeanFreePath(kinEnergy,particle,material,G4Region* region=0) |
---|
752 | </para></listitem> |
---|
753 | <listitem><para> |
---|
754 | PrintDEDXTable(particle) |
---|
755 | </para></listitem> |
---|
756 | <listitem><para> |
---|
757 | PrintRangeTable(particle) |
---|
758 | </para></listitem> |
---|
759 | <listitem><para> |
---|
760 | PrintInverseRangeTable(particle) |
---|
761 | </para></listitem> |
---|
762 | <listitem><para> |
---|
763 | ComputeDEDX(kinEnergy,particle,process,material,cut=DBL_MAX) |
---|
764 | </para></listitem> |
---|
765 | <listitem><para> |
---|
766 | ComputeElectronicDEDX(kinEnergy,particle,material,cut=DBL_MAX) |
---|
767 | </para></listitem> |
---|
768 | <listitem><para> |
---|
769 | ComputeNuclearDEDX(kinEnergy,particle,material,cut=DBL_MAX) |
---|
770 | </para></listitem> |
---|
771 | <listitem><para> |
---|
772 | ComputeTotalDEDX(kinEnergy,particle,material,cut=DBL_MAX) |
---|
773 | </para></listitem> |
---|
774 | <listitem><para> |
---|
775 | ComputeCrosSectionPerVolume(kinEnergy,particle,process,material,cut=0) |
---|
776 | </para></listitem> |
---|
777 | <listitem><para> |
---|
778 | ComputeCrosSectionPerAtom(kinEnergy,particle,process,Z,A,cut=0) |
---|
779 | </para></listitem> |
---|
780 | <listitem><para> |
---|
781 | ComputeMeanFreePath(kinEnergy,particle,process,material,cut=0) |
---|
782 | </para></listitem> |
---|
783 | <listitem><para> |
---|
784 | ComputeEnergyCutFromRangeCut(range,particle,material) |
---|
785 | </para></listitem> |
---|
786 | <listitem><para> |
---|
787 | FindParticle(const G4String&) |
---|
788 | </para></listitem> |
---|
789 | <listitem><para> |
---|
790 | FindIon(G4int Z, G4int A) |
---|
791 | </para></listitem> |
---|
792 | <listitem><para> |
---|
793 | FindMaterial(const G4String&) |
---|
794 | </para></listitem> |
---|
795 | <listitem><para> |
---|
796 | FindRegion(const G4String&) |
---|
797 | </para></listitem> |
---|
798 | <listitem><para> |
---|
799 | FindCouple(const G4Material*, const G4Region* region=0) |
---|
800 | </para></listitem> |
---|
801 | <listitem><para> |
---|
802 | SetVerbose(G4int) |
---|
803 | </para></listitem> |
---|
804 | </itemizedlist> |
---|
805 | </para> |
---|
806 | |
---|
807 | <para> |
---|
808 | For these interfaces, particles, materials, or processes may be |
---|
809 | pointers or strings with names. |
---|
810 | </para> |
---|
811 | |
---|
812 | </sect3> |
---|
813 | |
---|
814 | |
---|
815 | <!-- ******************* Section (Level#3) ****************** --> |
---|
816 | <sect3 id="sect.PhysProc.EleMag.LowE"> |
---|
817 | <title> |
---|
818 | Low Energy Electromagnetic Processes |
---|
819 | </title> |
---|
820 | |
---|
821 | <para> |
---|
822 | A physical interaction is described by a process class which can handle |
---|
823 | physics models, described by model classes. The following is a summary |
---|
824 | of the Low Energy Electromagnetic physics models available in Geant4. |
---|
825 | Further information is available in the web pages of the |
---|
826 | Geant4 Low Energy Electromagnetic Physics Working Group, accessible |
---|
827 | from the Geant4 web site, “who we are” section, then “working groups”. |
---|
828 | </para> |
---|
829 | |
---|
830 | <para> |
---|
831 | The physics content of these models is documented in the Geant4 |
---|
832 | <ulink url="http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/PhysicsReferenceManual/html/PhysicsReferenceManual.html"> |
---|
833 | Physics Reference Manual. |
---|
834 | </ulink> |
---|
835 | They are based on the Livermore data library, on the |
---|
836 | ICRU73 data tables or on the Penelope Monte Carlo code. They adopt the |
---|
837 | same software design as the "standard" Geant4 electromagnetic models. |
---|
838 | </para> |
---|
839 | |
---|
840 | <para> |
---|
841 | Examples of the registration of physics constructor with low-energy |
---|
842 | electromagnetic models are shown in Geant4 extended examples |
---|
843 | (<literal>$G4INSTALL/examples/extended/electromagnetic</literal>). |
---|
844 | Advanced examples (<literal>$G4INSTALL/examples/advanced</literal>) |
---|
845 | illustrate alternative instantiation of these processes. |
---|
846 | Both are available as part of the Geant4 release. |
---|
847 | </para> |
---|
848 | |
---|
849 | <para> |
---|
850 | To use the low energy electromagnetic models, data files need to be |
---|
851 | copied by the user to his/her code repository. These files are |
---|
852 | distributed together with Geant4. The user should set the environment |
---|
853 | variable G4LEDATA to the directory where he/she has copied the files. |
---|
854 | </para> |
---|
855 | |
---|
856 | <!-- ******************* Section (Level#4) ****************** --> |
---|
857 | <sect4 id="sect.PhysProc.EleMag.LowE.Livemore"> |
---|
858 | <title> |
---|
859 | Livermore based models |
---|
860 | </title> |
---|
861 | |
---|
862 | <para> |
---|
863 | <itemizedlist spacing="compact"> |
---|
864 | <listitem><para> |
---|
865 | <emphasis role="bold">Photon models</emphasis> |
---|
866 | <itemizedlist spacing="compact"> |
---|
867 | <listitem><para> |
---|
868 | Photo-electric effect (class <emphasis>G4LivermorePhotoElectricModel</emphasis>) |
---|
869 | </para></listitem> |
---|
870 | <listitem><para> |
---|
871 | Polarized Photo-electric effect (class <emphasis>G4LivermorePolarizedPhotoElectricModel</emphasis>) |
---|
872 | </para></listitem> |
---|
873 | <listitem><para> |
---|
874 | Compton scattering (class <emphasis>G4LivermoreComptonModel</emphasis>) |
---|
875 | </para></listitem> |
---|
876 | <listitem><para> |
---|
877 | Polarized Compton scattering (class <emphasis>G4LivermorePolarizedComptonModel</emphasis>) |
---|
878 | </para></listitem> |
---|
879 | <listitem><para> |
---|
880 | Rayleigh scattering (class <emphasis>G4LivermoreRayleighModel</emphasis>) |
---|
881 | </para></listitem> |
---|
882 | <listitem><para> |
---|
883 | Polarized Rayleigh scattering (class <emphasis>G4LivermorePolarizedRayleighModel</emphasis>) |
---|
884 | </para></listitem> |
---|
885 | <listitem><para> |
---|
886 | Gamma conversion (also called pair production, class <emphasis>G4LivermoreGammaConversionModel</emphasis>) |
---|
887 | </para></listitem> |
---|
888 | <listitem><para> |
---|
889 | Polarized gamma conversion (class <emphasis>G4LivermorePolarizedGammaConversionModel</emphasis>) |
---|
890 | </para></listitem> |
---|
891 | </itemizedlist> |
---|
892 | </para></listitem> |
---|
893 | <listitem><para> |
---|
894 | <emphasis role="bold">Electron models</emphasis> |
---|
895 | <itemizedlist spacing="compact"> |
---|
896 | <listitem><para> |
---|
897 | Bremsstrahlung (class <emphasis>G4LivermoreBremsstrahlungModel</emphasis>) |
---|
898 | </para></listitem> |
---|
899 | <listitem><para> |
---|
900 | Ionisation and delta ray production (class <emphasis>G4LivermoreIonisationModel</emphasis>) |
---|
901 | </para></listitem> |
---|
902 | </itemizedlist> |
---|
903 | </para></listitem> |
---|
904 | </itemizedlist> |
---|
905 | </para> |
---|
906 | |
---|
907 | <para> |
---|
908 | Options can be set in the G4LivermorePhotoElectricModel class, that allow |
---|
909 | the use of alternative photoelectron angular generators: |
---|
910 | |
---|
911 | <itemizedlist spacing="compact"> |
---|
912 | <listitem><para> |
---|
913 | SetAngularGenerator(G4VPhotoElectricAngularDistribution* distribution); |
---|
914 | </para></listitem> |
---|
915 | <listitem><para> |
---|
916 | SetAngularGenerator(const G4String& name); |
---|
917 | </para></listitem> |
---|
918 | </itemizedlist> |
---|
919 | </para> |
---|
920 | |
---|
921 | <para> |
---|
922 | Currently three angular generators are available: |
---|
923 | G4PhotoElectricAngularGeneratorSimple, G4PhotoElectricAngularGeneratorSauterGavrilla |
---|
924 | and G4PhotoElectricAngularGeneratorPolarized. |
---|
925 | G4PhotoElectricAngularGeneratorSauterGavrilla is selected by default. |
---|
926 | G4PhotoElectricAngularGeneratorSimple, G4PhotoElectricAngularGeneratorSauterGavrilla |
---|
927 | and G4PhotoElectricAngularGeneratorPolarized can be set using respectively the |
---|
928 | strings "default", "standard" and "polarized". |
---|
929 | </para> |
---|
930 | |
---|
931 | <para> |
---|
932 | Options are available in the G4LivermoreBremsstrahlungModel class, that allow |
---|
933 | the use of alternative bremsstrahlung angular generators: |
---|
934 | <itemizedlist spacing="compact"> |
---|
935 | <listitem><para> |
---|
936 | SetAngularGenerator(G4VBremAngularDistribution* distribution); |
---|
937 | </para></listitem> |
---|
938 | <listitem><para> |
---|
939 | SetAngularGenerator(const G4String& name); |
---|
940 | </para></listitem> |
---|
941 | </itemizedlist> |
---|
942 | </para> |
---|
943 | |
---|
944 | <para> |
---|
945 | Currently three angular generators are available: G4ModifiedTsai, |
---|
946 | 2BNGenerator and 2BSGenerator. G4ModifiedTsai is set by default, but it |
---|
947 | can be forced using the string "tsai". 2BNGenerator and 2BSGenerator |
---|
948 | can be set using the strings "2bs" and "2bn". Information regarding |
---|
949 | conditions of use, performance and energy |
---|
950 | limits of different models are available in the Physics Reference Manual . |
---|
951 | </para> |
---|
952 | |
---|
953 | <para> |
---|
954 | Other options G4LivermoreBremsstrahlungModel class are: |
---|
955 | |
---|
956 | <itemizedlist spacing="compact"> |
---|
957 | <listitem><para> |
---|
958 | SetCutForLowEnSecPhotons(G4double) |
---|
959 | </para></listitem> |
---|
960 | </itemizedlist> |
---|
961 | </para> |
---|
962 | |
---|
963 | <para> |
---|
964 | Options are available in the G4LivermoreIonisationModel class: |
---|
965 | |
---|
966 | <itemizedlist spacing="compact"> |
---|
967 | <listitem><para> |
---|
968 | ActivateAuger(G4bool) |
---|
969 | </para></listitem> |
---|
970 | <listitem><para> |
---|
971 | SetCutForLowEnSecPhotons(G4double) |
---|
972 | </para></listitem> |
---|
973 | <listitem><para> |
---|
974 | SetCutForLowEnSecElectrons(G4double) |
---|
975 | </para></listitem> |
---|
976 | </itemizedlist> |
---|
977 | </para> |
---|
978 | |
---|
979 | </sect4> |
---|
980 | |
---|
981 | |
---|
982 | <!-- ******************* Section (Level#4) ****************** --> |
---|
983 | <sect4 id="sect.PhysProc.EleMag.LowE.ICRU73"> |
---|
984 | <title> |
---|
985 | ICRU73 based ion model |
---|
986 | </title> |
---|
987 | |
---|
988 | <para> |
---|
989 | Ionisation and delta ray production (class G4IonParametrisedLossModel) |
---|
990 | </para> |
---|
991 | |
---|
992 | <para> |
---|
993 | The ion model uses ICRU 73 stopping powers, if corresponding ion-material |
---|
994 | combinations are covered by the ICRU 73 report (up to 1 GeV/nucleon), and |
---|
995 | otherwise applies a Bethe-Bloch based formalism. For compounds, ICRU 73 |
---|
996 | stopping powers are employed if the material name coincides with the name |
---|
997 | of Geant4 NIST materials (e.g. G4_WATER). Elemental materials are matched |
---|
998 | to the corresponding ICRU 73 stopping powers by means of the atomic number |
---|
999 | of the material. The material name may be arbitrary in this case. For a |
---|
1000 | list of applicable materials, the user is referred to the ICRU 73 report. |
---|
1001 | </para> |
---|
1002 | |
---|
1003 | <para> |
---|
1004 | The model requires data files to be copied by the user to his/her code |
---|
1005 | repository. These files are distributed together with the Geant4 release. |
---|
1006 | The user should set the environment variable G4LEDATA to the directory where |
---|
1007 | he/she has copied the files. |
---|
1008 | </para> |
---|
1009 | |
---|
1010 | <para> |
---|
1011 | The model is dedicated to be used with the G4ionIonisation process and its |
---|
1012 | applicability is restricted to G4GenericIon particles. The ion model is |
---|
1013 | not used by default by this process and must be instantiated and registered |
---|
1014 | by the user: |
---|
1015 | |
---|
1016 | <informalexample> |
---|
1017 | <programlisting> |
---|
1018 | G4ionIonisation* ionIoni = new G4ionIonisation(); |
---|
1019 | ionIoni -> SetEmModel(new G4IonParametrisedLossModel()); |
---|
1020 | </programlisting> |
---|
1021 | </informalexample> |
---|
1022 | </para> |
---|
1023 | |
---|
1024 | </sect4> |
---|
1025 | |
---|
1026 | <!-- ******************* Section (Level#4) ****************** --> |
---|
1027 | <sect4 id="sect.PhysProc.EleMag.LowE.Penelope"> |
---|
1028 | <title> |
---|
1029 | Penelope based models |
---|
1030 | </title> |
---|
1031 | |
---|
1032 | <para> |
---|
1033 | <itemizedlist spacing="compact"> |
---|
1034 | <listitem><para> |
---|
1035 | <emphasis role="bold">Photon models</emphasis> |
---|
1036 | <itemizedlist spacing="compact"> |
---|
1037 | <listitem><para> |
---|
1038 | Compton scattering (class <emphasis>G4PenelopeComptonModel</emphasis>) |
---|
1039 | </para></listitem> |
---|
1040 | <listitem><para> |
---|
1041 | Rayleigh scattering (class <emphasis>G4PenelopeRayleighModel</emphasis>) |
---|
1042 | </para></listitem> |
---|
1043 | <listitem><para> |
---|
1044 | Gamma conversion (also called pair production, class <emphasis>GPenelopeGammaConversionModel</emphasis>) |
---|
1045 | </para></listitem> |
---|
1046 | <listitem><para> |
---|
1047 | Photo-electric effect (class <emphasis>G4PenelopePhotoElectricModel</emphasis>) |
---|
1048 | </para></listitem> |
---|
1049 | </itemizedlist> |
---|
1050 | </para></listitem> |
---|
1051 | <listitem><para> |
---|
1052 | <emphasis role="bold">Electron models</emphasis> |
---|
1053 | <itemizedlist spacing="compact"> |
---|
1054 | <listitem><para> |
---|
1055 | Bremsstrahlung (class <emphasis>G4PenelopeBremsstrahlungModel</emphasis>) |
---|
1056 | </para></listitem> |
---|
1057 | <listitem><para> |
---|
1058 | Ionisation and delta ray production (class <emphasis>G4PenelopeIonisationModel</emphasis>) |
---|
1059 | </para></listitem> |
---|
1060 | </itemizedlist> |
---|
1061 | </para></listitem> |
---|
1062 | <listitem><para> |
---|
1063 | <emphasis role="bold">Positron models</emphasis> |
---|
1064 | <itemizedlist spacing="compact"> |
---|
1065 | <listitem><para> |
---|
1066 | Bremsstrahlung (class <emphasis>G4PenelopeBremsstrahlungModel</emphasis>) |
---|
1067 | </para></listitem> |
---|
1068 | <listitem><para> |
---|
1069 | Ionisation and delta ray production (class <emphasis>G4PenelopeIonisationModel</emphasis>) |
---|
1070 | </para></listitem> |
---|
1071 | <listitem><para> |
---|
1072 | Positron annihilation (class <emphasis>class G4PenelopeAnnihilationModel</emphasis>) |
---|
1073 | </para></listitem> |
---|
1074 | </itemizedlist> |
---|
1075 | </para></listitem> |
---|
1076 | </itemizedlist> |
---|
1077 | </para> |
---|
1078 | |
---|
1079 | <para> |
---|
1080 | All Penelope models can be applied up to a maximum energy of 100 GeV, |
---|
1081 | although it is advisable not to use them above a few hundreds of MeV. |
---|
1082 | </para> |
---|
1083 | |
---|
1084 | <para> |
---|
1085 | Options are available in the all Penelope Models, allowing to set |
---|
1086 | (and retrieve) the verbosity level of the model, namely the amount of |
---|
1087 | information which is printed on the screen. |
---|
1088 | |
---|
1089 | <itemizedlist spacing="compact"> |
---|
1090 | <listitem><para> |
---|
1091 | SetVerbosityLevel(G4int) |
---|
1092 | </para></listitem> |
---|
1093 | <listitem><para> |
---|
1094 | GetVerbosityLevel() |
---|
1095 | </para></listitem> |
---|
1096 | </itemizedlist> |
---|
1097 | </para> |
---|
1098 | |
---|
1099 | <para> |
---|
1100 | The default verbosity level is 0 (namely, no textual output on the screen). |
---|
1101 | The default value should be used in general for normal runs. Higher |
---|
1102 | verbosity levels are suggested only for testing and debugging purposes. |
---|
1103 | </para> |
---|
1104 | |
---|
1105 | <para> |
---|
1106 | The verbosity scale defined for all Penelope processes is the following: |
---|
1107 | |
---|
1108 | <itemizedlist spacing="compact"> |
---|
1109 | <listitem><para> |
---|
1110 | 0 = no printout on the screen (default) |
---|
1111 | </para></listitem> |
---|
1112 | <listitem><para> |
---|
1113 | 1 = issue warnings only in the case of energy non-conservation in the final state (should never happen) |
---|
1114 | </para></listitem> |
---|
1115 | <listitem><para> |
---|
1116 | 2 = reports full details on the energy budget in the final state |
---|
1117 | </para></listitem> |
---|
1118 | <listitem><para> |
---|
1119 | 3 = writes also informations on cross section calculation, data file opening and sampling of atoms |
---|
1120 | </para></listitem> |
---|
1121 | <listitem><para> |
---|
1122 | 4 = issues messages when entering in methods |
---|
1123 | </para></listitem> |
---|
1124 | </itemizedlist> |
---|
1125 | </para> |
---|
1126 | |
---|
1127 | <para> |
---|
1128 | Options are available in G4PenelopeComptonModel, G4PenelopePhotoElectricModel |
---|
1129 | and G4PenelopeIonisationModel to enable or disable the usage of atomic |
---|
1130 | de-excitation via the G4AtomicDeexcitation module. |
---|
1131 | |
---|
1132 | <itemizedlist spacing="compact"> |
---|
1133 | <listitem><para> |
---|
1134 | SetDeexcitationFlag(G4bool) |
---|
1135 | </para></listitem> |
---|
1136 | <listitem><para> |
---|
1137 | DeexcitationFlag() |
---|
1138 | </para></listitem> |
---|
1139 | </itemizedlist> |
---|
1140 | </para> |
---|
1141 | |
---|
1142 | <para> |
---|
1143 | The default is “true”, namely vacancies in atomic shells produced by the |
---|
1144 | interaction are handled by the G4AtomicDeexcitation module, possibly with |
---|
1145 | the subsequent emission of fluorescence x-rays. If is set to “false” |
---|
1146 | by the user, the energy released in the re-arrangement of atomic vacancies |
---|
1147 | is treated in the model as a local energy deposit, without emission of |
---|
1148 | secondary particles. The methods are actually inherited from G4VEmModel, |
---|
1149 | so they work for all Penelope models; by the way, they have effect only |
---|
1150 | in G4PenelopeComptonModel, G4PenelopePhotoElectricModel and |
---|
1151 | G4PenelopeIonisationModel. |
---|
1152 | </para> |
---|
1153 | |
---|
1154 | <para> |
---|
1155 | An option is also available in these models to enable the production of |
---|
1156 | Auger electrons by the G4AtomicDeexcitation module ActivateAuger(G4bool). |
---|
1157 | The default (coming from G4AtomicDeexcitation) is “false”, namely only |
---|
1158 | fluorescence x-rays are emitted but not Auger electrons. One should |
---|
1159 | notice that this option has effect only if the usage of the atomic |
---|
1160 | deexcitation is enabled. A warning message is printed if one tries to |
---|
1161 | enable the emission of the Auger electrons after having disabled the |
---|
1162 | atomic deexcitation via SetDeexcitationFlag(false). |
---|
1163 | </para> |
---|
1164 | |
---|
1165 | </sect4> |
---|
1166 | </sect3> |
---|
1167 | |
---|
1168 | |
---|
1169 | |
---|
1170 | <!-- ******************* Section (Level#3) ****************** --> |
---|
1171 | <sect3 id="sect.PhysProc.EleMag.VeryLowE"> |
---|
1172 | <title> |
---|
1173 | Very Low energy Electromagnetic Processes (Geant4-DNA extension) |
---|
1174 | </title> |
---|
1175 | |
---|
1176 | <para> |
---|
1177 | The Geant4 low energy electromagnetic Physics package has been extended |
---|
1178 | down to energies of a few electronVolts suitable for the simulation of |
---|
1179 | radiation effects in liquid water for applications in microdosimetry at |
---|
1180 | the cellular and sub-cellular level. These developments take place in |
---|
1181 | the framework of the on-going Geant4-DNA project (see the web pages |
---|
1182 | of the |
---|
1183 | <ulink url="http://geant4.web.cern.ch/geant4/collaboration/working_groups/LEelectromagnetic/">Geant4 Low Energy Electromagnetic Physics Working Group</ulink>). |
---|
1184 | </para> |
---|
1185 | |
---|
1186 | <para> |
---|
1187 | The Geant4-DNA process and model classes apply to electrons, protons, |
---|
1188 | hydrogen, alpha particles and their charge states. |
---|
1189 | </para> |
---|
1190 | |
---|
1191 | |
---|
1192 | <!-- ******* Bridgehead ******* --> |
---|
1193 | <bridgehead renderas='sect4'> |
---|
1194 | Electron processes and models |
---|
1195 | </bridgehead> |
---|
1196 | <para> |
---|
1197 | <itemizedlist spacing="compact"> |
---|
1198 | <listitem><para> |
---|
1199 | Elastic scattering : |
---|
1200 | <itemizedlist spacing="compact"> |
---|
1201 | <listitem><para> |
---|
1202 | process class is G4DNAElastic |
---|
1203 | </para></listitem> |
---|
1204 | <listitem><para> |
---|
1205 | two alternative model classes are : G4DNAScreenedRutherfordElasticModel |
---|
1206 | or G4DNAChampionElasticModel |
---|
1207 | </para></listitem> |
---|
1208 | </itemizedlist> |
---|
1209 | </para></listitem> |
---|
1210 | |
---|
1211 | <listitem><para> |
---|
1212 | Excitation |
---|
1213 | <itemizedlist spacing="compact"> |
---|
1214 | <listitem><para> |
---|
1215 | process class is G4DNAExcitation |
---|
1216 | </para></listitem> |
---|
1217 | <listitem><para> |
---|
1218 | model class is G4DNAEmfietzoglouExcitationModel |
---|
1219 | </para></listitem> |
---|
1220 | </itemizedlist> |
---|
1221 | </para></listitem> |
---|
1222 | |
---|
1223 | <listitem><para> |
---|
1224 | Ionisation |
---|
1225 | <itemizedlist spacing="compact"> |
---|
1226 | <listitem><para> |
---|
1227 | process class is G4DNAIonisation |
---|
1228 | </para></listitem> |
---|
1229 | <listitem><para> |
---|
1230 | model class is G4DNABornIonisationModel |
---|
1231 | </para></listitem> |
---|
1232 | </itemizedlist> |
---|
1233 | </para></listitem> |
---|
1234 | </itemizedlist> |
---|
1235 | </para> |
---|
1236 | |
---|
1237 | <!-- ******* Bridgehead ******* --> |
---|
1238 | <bridgehead renderas='sect4'> |
---|
1239 | Proton processes and models |
---|
1240 | </bridgehead> |
---|
1241 | <para> |
---|
1242 | <itemizedlist spacing="compact"> |
---|
1243 | <listitem><para> |
---|
1244 | Excitation |
---|
1245 | <itemizedlist spacing="compact"> |
---|
1246 | <listitem><para> |
---|
1247 | process class is G4DNAExcitation |
---|
1248 | </para></listitem> |
---|
1249 | <listitem><para> |
---|
1250 | two complementary model classes are G4DNAMillerGreenExcitationModel |
---|
1251 | (below 500 keV) and G4DNABornExcitationModel (above) |
---|
1252 | </para></listitem> |
---|
1253 | </itemizedlist> |
---|
1254 | </para></listitem> |
---|
1255 | |
---|
1256 | <listitem><para> |
---|
1257 | Ionisation |
---|
1258 | <itemizedlist spacing="compact"> |
---|
1259 | <listitem><para> |
---|
1260 | process class is G4DNAIonisation |
---|
1261 | </para></listitem> |
---|
1262 | <listitem><para> |
---|
1263 | two complementary model classes are G4DNARuddIonisationModel |
---|
1264 | (below 500 keV) and G4DNABornIonisationModel (above) |
---|
1265 | </para></listitem> |
---|
1266 | </itemizedlist> |
---|
1267 | </para></listitem> |
---|
1268 | |
---|
1269 | <listitem><para> |
---|
1270 | Charge decrease |
---|
1271 | <itemizedlist spacing="compact"> |
---|
1272 | <listitem><para> |
---|
1273 | process class is G4DNAChargeDecrease |
---|
1274 | </para></listitem> |
---|
1275 | <listitem><para> |
---|
1276 | model class is G4DNADingfelderChargeDecreaseModel |
---|
1277 | </para></listitem> |
---|
1278 | </itemizedlist> |
---|
1279 | </para></listitem> |
---|
1280 | </itemizedlist> |
---|
1281 | </para> |
---|
1282 | |
---|
1283 | <!-- ******* Bridgehead ******* --> |
---|
1284 | <bridgehead renderas='sect4'> |
---|
1285 | Hydrogen processes and models |
---|
1286 | </bridgehead> |
---|
1287 | <para> |
---|
1288 | <itemizedlist spacing="compact"> |
---|
1289 | <listitem><para> |
---|
1290 | Ionisation |
---|
1291 | <itemizedlist spacing="compact"> |
---|
1292 | <listitem><para> |
---|
1293 | process class is G4DNAIonisation |
---|
1294 | </para></listitem> |
---|
1295 | <listitem><para> |
---|
1296 | model class is G4DNARuddIonisationModel |
---|
1297 | </para></listitem> |
---|
1298 | </itemizedlist> |
---|
1299 | </para></listitem> |
---|
1300 | |
---|
1301 | <listitem><para> |
---|
1302 | Charge increase |
---|
1303 | <itemizedlist spacing="compact"> |
---|
1304 | <listitem><para> |
---|
1305 | process class is G4DNAChargeIncrease |
---|
1306 | </para></listitem> |
---|
1307 | <listitem><para> |
---|
1308 | model class is G4DNADingfelderChargeIncreaseModel |
---|
1309 | </para></listitem> |
---|
1310 | </itemizedlist> |
---|
1311 | </para></listitem> |
---|
1312 | </itemizedlist> |
---|
1313 | </para> |
---|
1314 | |
---|
1315 | <!-- ******* Bridgehead ******* --> |
---|
1316 | <bridgehead renderas='sect4'> |
---|
1317 | Helium (neutral) processes and models |
---|
1318 | </bridgehead> |
---|
1319 | <para> |
---|
1320 | <itemizedlist spacing="compact"> |
---|
1321 | <listitem><para> |
---|
1322 | Excitation |
---|
1323 | <itemizedlist spacing="compact"> |
---|
1324 | <listitem><para> |
---|
1325 | process class is G4DNAExcitation |
---|
1326 | </para></listitem> |
---|
1327 | <listitem><para> |
---|
1328 | model class is G4DNAMillerGreenExcitationModel |
---|
1329 | </para></listitem> |
---|
1330 | </itemizedlist> |
---|
1331 | </para></listitem> |
---|
1332 | |
---|
1333 | <listitem><para> |
---|
1334 | Ionisation |
---|
1335 | <itemizedlist spacing="compact"> |
---|
1336 | <listitem><para> |
---|
1337 | process class is G4DNAIonisation |
---|
1338 | </para></listitem> |
---|
1339 | <listitem><para> |
---|
1340 | model class is G4DNARuddIonisationModel |
---|
1341 | </para></listitem> |
---|
1342 | </itemizedlist> |
---|
1343 | </para></listitem> |
---|
1344 | |
---|
1345 | <listitem><para> |
---|
1346 | Charge increase |
---|
1347 | <itemizedlist spacing="compact"> |
---|
1348 | <listitem><para> |
---|
1349 | process class is G4DNAChargeIncrease |
---|
1350 | </para></listitem> |
---|
1351 | <listitem><para> |
---|
1352 | model class is G4DNADingfelderChargeIncreaseModel |
---|
1353 | </para></listitem> |
---|
1354 | </itemizedlist> |
---|
1355 | </para></listitem> |
---|
1356 | </itemizedlist> |
---|
1357 | </para> |
---|
1358 | |
---|
1359 | <!-- ******* Bridgehead ******* --> |
---|
1360 | <bridgehead renderas='sect4'> |
---|
1361 | Helium+ (ionized once) processes and models |
---|
1362 | </bridgehead> |
---|
1363 | <para> |
---|
1364 | <itemizedlist spacing="compact"> |
---|
1365 | <listitem><para> |
---|
1366 | Excitation |
---|
1367 | <itemizedlist spacing="compact"> |
---|
1368 | <listitem><para> |
---|
1369 | process class is G4DNAExcitation |
---|
1370 | </para></listitem> |
---|
1371 | <listitem><para> |
---|
1372 | model class is G4DNAMillerGreenExcitationModel |
---|
1373 | </para></listitem> |
---|
1374 | </itemizedlist> |
---|
1375 | </para></listitem> |
---|
1376 | |
---|
1377 | <listitem><para> |
---|
1378 | Ionisation |
---|
1379 | <itemizedlist spacing="compact"> |
---|
1380 | <listitem><para> |
---|
1381 | process class is G4DNAIonisation |
---|
1382 | </para></listitem> |
---|
1383 | <listitem><para> |
---|
1384 | model classes is G4DNARuddIonisationModel |
---|
1385 | </para></listitem> |
---|
1386 | </itemizedlist> |
---|
1387 | </para></listitem> |
---|
1388 | |
---|
1389 | <listitem><para> |
---|
1390 | Charge increase |
---|
1391 | <itemizedlist spacing="compact"> |
---|
1392 | <listitem><para> |
---|
1393 | process class is G4DNAChargeIncrease |
---|
1394 | </para></listitem> |
---|
1395 | <listitem><para> |
---|
1396 | model classes is G4DNADingfelderChargeIncreaseModel |
---|
1397 | </para></listitem> |
---|
1398 | </itemizedlist> |
---|
1399 | </para></listitem> |
---|
1400 | |
---|
1401 | <listitem><para> |
---|
1402 | Charge decrease |
---|
1403 | <itemizedlist spacing="compact"> |
---|
1404 | <listitem><para> |
---|
1405 | process class is G4DNAChargeDecrease |
---|
1406 | </para></listitem> |
---|
1407 | <listitem><para> |
---|
1408 | model classes is G4DNADingfelderChargeDecreaseModel |
---|
1409 | </para></listitem> |
---|
1410 | </itemizedlist> |
---|
1411 | </para></listitem> |
---|
1412 | </itemizedlist> |
---|
1413 | </para> |
---|
1414 | |
---|
1415 | <!-- ******* Bridgehead ******* --> |
---|
1416 | <bridgehead renderas='sect4'> |
---|
1417 | Helium++ (ionised twice) processes and models |
---|
1418 | </bridgehead> |
---|
1419 | <para> |
---|
1420 | <itemizedlist spacing="compact"> |
---|
1421 | <listitem><para> |
---|
1422 | Excitation |
---|
1423 | <itemizedlist spacing="compact"> |
---|
1424 | <listitem><para> |
---|
1425 | process class is G4DNAExcitation |
---|
1426 | </para></listitem> |
---|
1427 | <listitem><para> |
---|
1428 | model classes is G4DNAMillerGreenExcitationModel |
---|
1429 | </para></listitem> |
---|
1430 | </itemizedlist> |
---|
1431 | </para></listitem> |
---|
1432 | |
---|
1433 | <listitem><para> |
---|
1434 | Ionisation |
---|
1435 | <itemizedlist spacing="compact"> |
---|
1436 | <listitem><para> |
---|
1437 | process class is G4DNAIonisation |
---|
1438 | </para></listitem> |
---|
1439 | <listitem><para> |
---|
1440 | model classes is G4DNARuddIonisationModel |
---|
1441 | </para></listitem> |
---|
1442 | </itemizedlist> |
---|
1443 | </para></listitem> |
---|
1444 | |
---|
1445 | <listitem><para> |
---|
1446 | Charge decrease |
---|
1447 | <itemizedlist spacing="compact"> |
---|
1448 | <listitem><para> |
---|
1449 | process class is G4DNAChargeDecrease |
---|
1450 | </para></listitem> |
---|
1451 | <listitem><para> |
---|
1452 | model classes is G4DNADingfelderChargeDecreaseModel |
---|
1453 | </para></listitem> |
---|
1454 | </itemizedlist> |
---|
1455 | </para></listitem> |
---|
1456 | </itemizedlist> |
---|
1457 | </para> |
---|
1458 | |
---|
1459 | <para> |
---|
1460 | An example of the registration of these processes in a physics list is |
---|
1461 | given here below and may be found in the microdosimetry advanced example. |
---|
1462 | |
---|
1463 | |
---|
1464 | <informalexample> |
---|
1465 | <programlisting> |
---|
1466 | #include "G4DNAElastic.hh" |
---|
1467 | #include "G4DNAChampionElasticModel.hh" |
---|
1468 | #include "G4DNAScreenedRutherfordElasticModel.hh" |
---|
1469 | |
---|
1470 | #include "G4DNAExcitation.hh" |
---|
1471 | #include "G4DNAEmfietzoglouExcitationModel.hh" |
---|
1472 | #include "G4DNAMillerGreenExcitationModel.hh" |
---|
1473 | #include "G4DNABornExcitationModel.hh" |
---|
1474 | |
---|
1475 | #include "G4DNAIonisation.hh" |
---|
1476 | #include "G4DNABornIonisationModel.hh" |
---|
1477 | #include "G4DNARuddIonisationModel.hh" |
---|
1478 | |
---|
1479 | #include "G4DNAChargeDecrease.hh" |
---|
1480 | #include "G4DNADingfelderChargeDecreaseModel.hh" |
---|
1481 | |
---|
1482 | #include "G4DNAChargeIncrease.hh" |
---|
1483 | #include "G4DNADingfelderChargeIncreaseModel.hh" |
---|
1484 | |
---|
1485 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
---|
1486 | |
---|
1487 | void PhysicsList::ConstructEM() |
---|
1488 | { |
---|
1489 | theParticleIterator->reset(); |
---|
1490 | |
---|
1491 | while( (*theParticleIterator)() ) |
---|
1492 | { |
---|
1493 | |
---|
1494 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
1495 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
1496 | G4String particleName = particle->GetParticleName(); |
---|
1497 | |
---|
1498 | // DNA processes per particle type |
---|
1499 | |
---|
1500 | if (particleName == "e-") { |
---|
1501 | |
---|
1502 | G4DNAElastic* theDNAElasticProcess = new G4DNAElastic("e-_G4DNAElastic"); |
---|
1503 | theDNAElasticProcess->SetModel(new G4DNAChampionElasticModel()); |
---|
1504 | // or alternative model |
---|
1505 | // theDNAElasticProcess->SetModel(new G4DNAScreenedRutherfordElasticModel()); |
---|
1506 | pmanager->AddDiscreteProcess(theDNAElasticProcess); |
---|
1507 | |
---|
1508 | pmanager->AddDiscreteProcess(new G4DNAExcitation("e-_G4DNAExcitation")); |
---|
1509 | pmanager->AddDiscreteProcess(new G4DNAIonisation("e-_G4DNAIonisation")); |
---|
1510 | |
---|
1511 | } else if ( particleName == "proton" ) { |
---|
1512 | |
---|
1513 | pmanager->AddDiscreteProcess(new G4DNAExcitation("proton_G4DNAExcitation")); |
---|
1514 | pmanager->AddDiscreteProcess(new G4DNAIonisation("proton_G4DNAIonisation")); |
---|
1515 | pmanager->AddDiscreteProcess(new G4DNAChargeDecrease("proton_G4DNAChargeDecrease")); |
---|
1516 | |
---|
1517 | } else if ( particleName == "hydrogen" ) { |
---|
1518 | |
---|
1519 | pmanager->AddDiscreteProcess(new G4DNAIonisation("hydrogen_G4DNAIonisation")); |
---|
1520 | pmanager->AddDiscreteProcess(new G4DNAChargeIncrease("hydrogen_G4DNAChargeIncrease")); |
---|
1521 | |
---|
1522 | } else if ( particleName == "alpha" ) { |
---|
1523 | |
---|
1524 | pmanager->AddDiscreteProcess(new G4DNAExcitation("alpha_G4DNAExcitation")); |
---|
1525 | pmanager->AddDiscreteProcess(new G4DNAIonisation("alpha_G4DNAIonisation")); |
---|
1526 | pmanager->AddDiscreteProcess(new G4DNAChargeDecrease("alpha_G4DNAChargeDecrease")); |
---|
1527 | |
---|
1528 | } else if ( particleName == "alpha+" ) { |
---|
1529 | |
---|
1530 | pmanager->AddDiscreteProcess(new G4DNAExcitation("alpha+_G4DNAExcitation")); |
---|
1531 | pmanager->AddDiscreteProcess(new G4DNAIonisation("alpha+_G4DNAIonisation")); |
---|
1532 | pmanager->AddDiscreteProcess(new G4DNAChargeDecrease("alpha+_G4DNAChargeDecrease")); |
---|
1533 | pmanager->AddDiscreteProcess(new G4DNAChargeIncrease("alpha+_G4DNAChargeIncrease")); |
---|
1534 | |
---|
1535 | } else if ( particleName == "helium" ) { |
---|
1536 | |
---|
1537 | pmanager->AddDiscreteProcess(new G4DNAExcitation("helium_G4DNAExcitation")); |
---|
1538 | pmanager->AddDiscreteProcess(new G4DNAIonisation("helium_G4DNAIonisation")); |
---|
1539 | pmanager->AddDiscreteProcess(new G4DNAChargeIncrease("helium_G4DNAChargeIncrease")); |
---|
1540 | |
---|
1541 | } |
---|
1542 | |
---|
1543 | } // Loop on particles |
---|
1544 | } |
---|
1545 | |
---|
1546 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
---|
1547 | </programlisting> |
---|
1548 | </informalexample> |
---|
1549 | </para> |
---|
1550 | |
---|
1551 | <para> |
---|
1552 | Note that in the above example, "alpha" particles are helium atoms ionised |
---|
1553 | twice and "helium" particles are neutral helium atoms. The definition of |
---|
1554 | particles in the physics list may be for example implemented as follows : |
---|
1555 | |
---|
1556 | <informalexample> |
---|
1557 | <programlisting> |
---|
1558 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
1559 | |
---|
1560 | #include "G4DNAGenericIonsManager.hh" |
---|
1561 | void PhysicsList::ConstructBaryons() |
---|
1562 | { |
---|
1563 | // construct baryons --- |
---|
1564 | // Geant4 DNA particles |
---|
1565 | G4GenericIon::GenericIonDefinition() ; |
---|
1566 | G4DNAGenericIonsManager * genericIonsManager; |
---|
1567 | genericIonsManager=G4DNAGenericIonsManager::Instance(); |
---|
1568 | genericIonsManager->GetIon("alpha++"); |
---|
1569 | genericIonsManager->GetIon("alpha+"); |
---|
1570 | genericIonsManager->GetIon("helium"); |
---|
1571 | genericIonsManager->GetIon("hydrogen"); |
---|
1572 | } |
---|
1573 | |
---|
1574 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
1575 | </programlisting> |
---|
1576 | </informalexample> |
---|
1577 | </para> |
---|
1578 | |
---|
1579 | <para> |
---|
1580 | To run the Geant4-DNA extension, data files need to be copied by the |
---|
1581 | user to his/her code repository. These files are distributed together |
---|
1582 | with the Geant4 release. The user should set the environment variable |
---|
1583 | G4LEDATA to the directory where he/she has copied the files. |
---|
1584 | </para> |
---|
1585 | |
---|
1586 | </sect3> |
---|
1587 | </sect2> |
---|
1588 | |
---|
1589 | |
---|
1590 | <!-- ******************* Section (Level#2) ****************** --> |
---|
1591 | <sect2 id="sect.PhysProc.Had"> |
---|
1592 | <title> |
---|
1593 | Hadronic Interactions |
---|
1594 | </title> |
---|
1595 | |
---|
1596 | <para> |
---|
1597 | This section briefly introduces the hadronic physics processes |
---|
1598 | installed in Geant4. For details of the implementation of hadronic |
---|
1599 | interactions available in Geant4, please refer to the |
---|
1600 | <ulink url="http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/PhysicsReferenceManual/html/PhysicsReferenceManual.html"> |
---|
1601 | <emphasis role="bold">Physics Reference Manual</emphasis></ulink>. |
---|
1602 | </para> |
---|
1603 | |
---|
1604 | <!-- ******************* Section (Level#3) ****************** --> |
---|
1605 | <sect3 id="sect.PhysProc.Had.TreatCross"> |
---|
1606 | <title> |
---|
1607 | Treatment of Cross Sections |
---|
1608 | </title> |
---|
1609 | |
---|
1610 | <!-- ******* Bridgehead ******* --> |
---|
1611 | <bridgehead renderas='sect4'> |
---|
1612 | Cross section data sets |
---|
1613 | </bridgehead> |
---|
1614 | |
---|
1615 | <para> |
---|
1616 | Each hadronic process object (derived from |
---|
1617 | <emphasis>G4HadronicProcess</emphasis>) may have one or more cross section data |
---|
1618 | sets associated with it. The term "data set" is meant, in a broad |
---|
1619 | sense, to be an object that encapsulates methods and data for |
---|
1620 | calculating total cross sections for a given process. The methods |
---|
1621 | and data may take many forms, from a simple equation using a few |
---|
1622 | hard-wired numbers to a sophisticated parameterisation using large |
---|
1623 | data tables. Cross section data sets are derived from the abstract |
---|
1624 | class <emphasis>G4VCrossSectionDataSet</emphasis>, and are required to implement |
---|
1625 | the following methods: |
---|
1626 | |
---|
1627 | <informalexample> |
---|
1628 | <programlisting> |
---|
1629 | G4bool IsApplicable( const G4DynamicParticle*, const G4Element* ) |
---|
1630 | </programlisting> |
---|
1631 | </informalexample> |
---|
1632 | </para> |
---|
1633 | |
---|
1634 | <para> |
---|
1635 | This method must return <literal>True</literal> if the data set is able to |
---|
1636 | calculate a total cross section for the given particle and |
---|
1637 | material, and <literal>False</literal> otherwise. |
---|
1638 | |
---|
1639 | <informalexample> |
---|
1640 | <programlisting> |
---|
1641 | G4double GetCrossSection( const G4DynamicParticle*, const G4Element* ) |
---|
1642 | </programlisting> |
---|
1643 | </informalexample> |
---|
1644 | </para> |
---|
1645 | |
---|
1646 | <para> |
---|
1647 | This method, which will be invoked only if <literal>True</literal> was |
---|
1648 | returned by <literal>IsApplicable</literal>, must return a cross section, in |
---|
1649 | Geant4 default units, for the given particle and material. |
---|
1650 | |
---|
1651 | <informalexample> |
---|
1652 | <programlisting> |
---|
1653 | void BuildPhysicsTable( const G4ParticleDefinition& ) |
---|
1654 | </programlisting> |
---|
1655 | </informalexample> |
---|
1656 | </para> |
---|
1657 | |
---|
1658 | <para> |
---|
1659 | This method may be invoked to request the data set to recalculate |
---|
1660 | its internal database or otherwise reset its state after a change |
---|
1661 | in the cuts or other parameters of the given particle type. |
---|
1662 | |
---|
1663 | |
---|
1664 | <informalexample> |
---|
1665 | <programlisting> |
---|
1666 | void DumpPhysicsTable( const G4ParticleDefinition& ) = 0 |
---|
1667 | </programlisting> |
---|
1668 | </informalexample> |
---|
1669 | </para> |
---|
1670 | |
---|
1671 | <para> |
---|
1672 | This method may be invoked to request the data set to print its |
---|
1673 | internal database and/or other state information, for the given |
---|
1674 | particle type, to the standard output stream. |
---|
1675 | </para> |
---|
1676 | |
---|
1677 | <!-- ******* Bridgehead ******* --> |
---|
1678 | <bridgehead renderas='sect4'> |
---|
1679 | Cross section data store |
---|
1680 | </bridgehead> |
---|
1681 | |
---|
1682 | <para> |
---|
1683 | Cross section data sets are used by the process for the |
---|
1684 | calculation of the physical interaction length. A given cross |
---|
1685 | section data set may only apply to a certain energy range, or may |
---|
1686 | only be able to calculate cross sections for a particular type of |
---|
1687 | particle. The class <emphasis>G4CrossSectionDataStore</emphasis> has been |
---|
1688 | provided to allow the user to specify, if desired, a series of data |
---|
1689 | sets for a process, and to arrange the priority of data sets so |
---|
1690 | that the appropriate one is used for a given energy range, |
---|
1691 | particle, and material. It implements the following public |
---|
1692 | methods: |
---|
1693 | |
---|
1694 | <informalexample> |
---|
1695 | <programlisting> |
---|
1696 | G4CrossSectionDataStore() |
---|
1697 | |
---|
1698 | ~G4CrossSectionDataStore() |
---|
1699 | </programlisting> |
---|
1700 | </informalexample> |
---|
1701 | |
---|
1702 | and |
---|
1703 | |
---|
1704 | <informalexample> |
---|
1705 | <programlisting> |
---|
1706 | G4double GetCrossSection( const G4DynamicParticle*, const G4Element* ) |
---|
1707 | </programlisting> |
---|
1708 | </informalexample> |
---|
1709 | </para> |
---|
1710 | |
---|
1711 | <para> |
---|
1712 | For a given particle and material, this method returns a cross |
---|
1713 | section value provided by one of the collection of cross section |
---|
1714 | data sets listed in the data store object. If there are no known |
---|
1715 | data sets, a <literal>G4Exception</literal> is thrown and <literal>DBL_MIN</literal> is |
---|
1716 | returned. Otherwise, each data set in the list is queried, in |
---|
1717 | reverse list order, by invoking its <literal>IsApplicable</literal> method |
---|
1718 | for the given particle and material. The first data set object that |
---|
1719 | responds positively will then be asked to return a cross section |
---|
1720 | value via its <literal>GetCrossSection</literal> method. If no data set |
---|
1721 | responds positively, a <literal>G4Exception</literal> is thrown and |
---|
1722 | <literal>DBL_MIN</literal> is returned. |
---|
1723 | </para> |
---|
1724 | |
---|
1725 | <para> |
---|
1726 | <informalexample> |
---|
1727 | <programlisting> |
---|
1728 | void AddDataSet( G4VCrossSectionDataSet* aDataSet ) |
---|
1729 | </programlisting> |
---|
1730 | </informalexample> |
---|
1731 | |
---|
1732 | This method adds the given cross section data set to the end of the |
---|
1733 | list of data sets in the data store. For the evaluation of cross |
---|
1734 | sections, the list has a LIFO (Last In First Out) priority, meaning |
---|
1735 | that data sets added later to the list will have priority over |
---|
1736 | those added earlier to the list. Another way of saying this, is |
---|
1737 | that the data store, when given a <literal>GetCrossSection</literal> request, |
---|
1738 | does the <literal>IsApplicable</literal> queries in the reverse list order, |
---|
1739 | starting with the last data set in the list and proceeding to the |
---|
1740 | first, and the first data set that responds positively is used to |
---|
1741 | calculate the cross section. |
---|
1742 | </para> |
---|
1743 | |
---|
1744 | <para> |
---|
1745 | <informalexample> |
---|
1746 | <programlisting> |
---|
1747 | void BuildPhysicsTable( const G4ParticleDefinition& aParticleType ) |
---|
1748 | </programlisting> |
---|
1749 | </informalexample> |
---|
1750 | |
---|
1751 | This method may be invoked to indicate to the data store that there |
---|
1752 | has been a change in the cuts or other parameters of the given |
---|
1753 | particle type. In response, the data store will invoke the |
---|
1754 | <literal>BuildPhysicsTable</literal> of each of its data sets. |
---|
1755 | </para> |
---|
1756 | |
---|
1757 | <para> |
---|
1758 | <informalexample> |
---|
1759 | <programlisting> |
---|
1760 | void DumpPhysicsTable( const G4ParticleDefinition& ) |
---|
1761 | </programlisting> |
---|
1762 | </informalexample> |
---|
1763 | |
---|
1764 | This method may be used to request the data store to invoke the |
---|
1765 | <literal>DumpPhysicsTable</literal> method of each of its data sets. |
---|
1766 | </para> |
---|
1767 | |
---|
1768 | <!-- ******* Bridgehead ******* --> |
---|
1769 | <bridgehead renderas='sect4'> |
---|
1770 | Default cross sections |
---|
1771 | </bridgehead> |
---|
1772 | |
---|
1773 | <para> |
---|
1774 | The defaults for total cross section data and calculations have |
---|
1775 | been encapsulated in the singleton class |
---|
1776 | <emphasis>G4HadronCrossSections</emphasis>. Each hadronic process: |
---|
1777 | <emphasis>G4HadronInelasticProcess</emphasis>, |
---|
1778 | <emphasis>G4HadronElasticProcess</emphasis>, |
---|
1779 | <emphasis>G4HadronFissionProcess</emphasis>, |
---|
1780 | and <emphasis>G4HadronCaptureProcess</emphasis>, |
---|
1781 | comes already equipped with a cross section data store and a |
---|
1782 | default cross section data set. The data set objects are really |
---|
1783 | just shells that invoke the singleton <emphasis>G4HadronCrossSections</emphasis> |
---|
1784 | to do the real work of calculating cross sections. |
---|
1785 | </para> |
---|
1786 | |
---|
1787 | <para> |
---|
1788 | The default cross sections can be overridden in whole or in part |
---|
1789 | by the user. To this end, the base class <emphasis>G4HadronicProcess</emphasis> |
---|
1790 | has a ``get'' method: |
---|
1791 | |
---|
1792 | <informalexample> |
---|
1793 | <programlisting> |
---|
1794 | G4CrossSectionDataStore* GetCrossSectionDataStore() |
---|
1795 | </programlisting> |
---|
1796 | </informalexample> |
---|
1797 | |
---|
1798 | which gives public access to the data store for each process. The |
---|
1799 | user's cross section data sets can be added to the data store |
---|
1800 | according to the following framework: |
---|
1801 | |
---|
1802 | <informalexample> |
---|
1803 | <programlisting> |
---|
1804 | G4Hadron...Process aProcess(...) |
---|
1805 | |
---|
1806 | MyCrossSectionDataSet myDataSet(...) |
---|
1807 | |
---|
1808 | aProcess.GetCrossSectionDataStore()->AddDataSet( &MyDataSet ) |
---|
1809 | </programlisting> |
---|
1810 | </informalexample> |
---|
1811 | </para> |
---|
1812 | |
---|
1813 | <para> |
---|
1814 | The added data set will override the default cross section data |
---|
1815 | whenever so indicated by its <literal>IsApplicable</literal> method. |
---|
1816 | </para> |
---|
1817 | |
---|
1818 | <para> |
---|
1819 | In addition to the ``get'' method, <emphasis>G4HadronicProcess</emphasis> also |
---|
1820 | has the method |
---|
1821 | |
---|
1822 | <informalexample> |
---|
1823 | <programlisting> |
---|
1824 | void SetCrossSectionDataStore( G4CrossSectionDataStore* ) |
---|
1825 | </programlisting> |
---|
1826 | </informalexample> |
---|
1827 | |
---|
1828 | which allows the user to completely replace the default data |
---|
1829 | store with a new data store. |
---|
1830 | </para> |
---|
1831 | |
---|
1832 | <para> |
---|
1833 | It should be noted that a process does not send any information |
---|
1834 | about itself to its associated data store (and hence data set) |
---|
1835 | objects. Thus, each data set is assumed to be formulated to |
---|
1836 | calculate cross sections for one and only one type of process. Of |
---|
1837 | course, this does not prevent different data sets from sharing |
---|
1838 | common data and/or calculation methods, as in the case of the |
---|
1839 | <emphasis>G4HadronCrossSections</emphasis> class mentioned above. Indeed, |
---|
1840 | <emphasis>G4VCrossSectionDataSet</emphasis> specifies only the abstract interface |
---|
1841 | between physics processes and their data sets, and leaves the user |
---|
1842 | free to implement whatever sort of underlying structure is |
---|
1843 | appropriate. |
---|
1844 | </para> |
---|
1845 | |
---|
1846 | <para> |
---|
1847 | The current implementation of the data set |
---|
1848 | <emphasis>G4HadronCrossSections</emphasis> reuses the total cross-sections for |
---|
1849 | inelastic and elastic scattering, radiative capture and fission as |
---|
1850 | used with <emphasis role="bold">GHEISHA</emphasis> to provide cross-sections |
---|
1851 | for calculation |
---|
1852 | of the respective mean free paths of a given particle in a given |
---|
1853 | material. |
---|
1854 | </para> |
---|
1855 | |
---|
1856 | <!-- ******* Bridgehead ******* --> |
---|
1857 | <bridgehead renderas='sect4'> |
---|
1858 | Cross-sections for low energy neutron transport |
---|
1859 | </bridgehead> |
---|
1860 | |
---|
1861 | <para> |
---|
1862 | The cross section data for low energy neutron transport are |
---|
1863 | organized in a set of files that are read in by the corresponding |
---|
1864 | data set classes at time zero. Hereby the file system is used, in |
---|
1865 | order to allow highly granular access to the data. The ``root'' |
---|
1866 | directory of the cross-section directory structure is accessed |
---|
1867 | through an environment variable, <literal>NeutronHPCrossSections</literal>, |
---|
1868 | which is to be set by the user. The classes accessing the total |
---|
1869 | cross-sections of the individual processes, i.e., the cross-section |
---|
1870 | data set classes for low energy neutron transport, are |
---|
1871 | <emphasis>G4NeutronHPElasticData</emphasis>, |
---|
1872 | <emphasis>G4NeutronHPCaptureData</emphasis>, |
---|
1873 | <emphasis>G4NeutronHPFissionData</emphasis>, |
---|
1874 | and <emphasis>G4NeutronHPInelasticData</emphasis>. |
---|
1875 | </para> |
---|
1876 | |
---|
1877 | <para> |
---|
1878 | For detailed descriptions of the low energy neutron total |
---|
1879 | cross-sections, they may be registered by the user as described |
---|
1880 | above with the data stores of the corresponding processes for |
---|
1881 | neutron interactions. |
---|
1882 | </para> |
---|
1883 | |
---|
1884 | <para> |
---|
1885 | It should be noted that using these total cross section classes |
---|
1886 | does not require that the neutron_hp models also be used. It is up |
---|
1887 | to the user to decide whethee this is desirable or not for his |
---|
1888 | particular problem. |
---|
1889 | </para> |
---|
1890 | |
---|
1891 | <para> |
---|
1892 | A prototype of the compact version of neutron cross sections derived from HP database |
---|
1893 | are provided with new classes <emphasis>G4NeutronHPElasticData</emphasis>, |
---|
1894 | <emphasis>G4NeutronCaptureXS</emphasis>, |
---|
1895 | <emphasis>G4NeutronElasticXS</emphasis>, |
---|
1896 | and <emphasis>G4NeutronInelasticXS</emphasis>. |
---|
1897 | </para> |
---|
1898 | |
---|
1899 | </sect3> |
---|
1900 | |
---|
1901 | <!-- ******************* Section (Level#3) ****************** --> |
---|
1902 | <sect3 id="sect.PhysProc.Had.AtRest"> |
---|
1903 | <title> |
---|
1904 | Hadrons at Rest |
---|
1905 | </title> |
---|
1906 | |
---|
1907 | <!-- ******* Bridgehead ******* --> |
---|
1908 | <bridgehead renderas='sect4'> |
---|
1909 | List of implemented "Hadron at Rest" processes |
---|
1910 | </bridgehead> |
---|
1911 | |
---|
1912 | <para> |
---|
1913 | The following process classes have been implemented: |
---|
1914 | |
---|
1915 | <itemizedlist spacing="compact"> |
---|
1916 | <listitem><para> |
---|
1917 | pi- absorption (class name <emphasis>G4PionMinusAbsorptionAtRest</emphasis> |
---|
1918 | or <emphasis>G4PiMinusAbsorptionAtRest</emphasis>) |
---|
1919 | </para></listitem> |
---|
1920 | <listitem><para> |
---|
1921 | kaon- absorption (class name <emphasis>G4KaonMinusAbsorptionAtRest</emphasis> |
---|
1922 | or <emphasis>G4KaonMinusAbsorption</emphasis>) |
---|
1923 | </para></listitem> |
---|
1924 | <listitem><para> |
---|
1925 | neutron capture (class name <emphasis>G4NeutronCaptureAtRest</emphasis>) |
---|
1926 | </para></listitem> |
---|
1927 | <listitem><para> |
---|
1928 | anti-proton annihilation (class name |
---|
1929 | <emphasis>G4AntiProtonAnnihilationAtRest</emphasis>) |
---|
1930 | </para></listitem> |
---|
1931 | <listitem><para> |
---|
1932 | anti-neutron annihilation (class name |
---|
1933 | <emphasis>G4AntiNeutronAnnihilationAtRest</emphasis>) |
---|
1934 | </para></listitem> |
---|
1935 | <listitem><para> |
---|
1936 | mu- capture (class name <emphasis>G4MuonMinusCaptureAtRest</emphasis>) |
---|
1937 | </para></listitem> |
---|
1938 | <listitem><para> |
---|
1939 | alternative CHIPS model for any negativly charged particle |
---|
1940 | (class name <emphasis>G4QCaptureAtRest</emphasis>) |
---|
1941 | </para></listitem> |
---|
1942 | </itemizedlist> |
---|
1943 | </para> |
---|
1944 | |
---|
1945 | <para> |
---|
1946 | Obviously the last process does not, strictly speaking, deal with a |
---|
1947 | ``hadron at rest''. It does, nonetheless, share common features |
---|
1948 | with the others in the above list because of the implementation |
---|
1949 | model chosen. The differences between the alternative |
---|
1950 | implementation for kaon and pion absorption concern the fast part |
---|
1951 | of the emitted particle spectrum. G4PiMinusAbsorptionAtRest, and |
---|
1952 | G4KaonMinusAbsorptionAtRest focus especially on a good description |
---|
1953 | of this part of the spectrum. |
---|
1954 | </para> |
---|
1955 | |
---|
1956 | <!-- ******* Bridgehead ******* --> |
---|
1957 | <bridgehead renderas='sect4'> |
---|
1958 | Implementation Interface to Geant4 |
---|
1959 | </bridgehead> |
---|
1960 | |
---|
1961 | <para> |
---|
1962 | All of these classes are derived from the abstract class |
---|
1963 | <emphasis>G4VRestProcess</emphasis>. In addition to the constructor and |
---|
1964 | destructor methods, the following public methods of the abstract |
---|
1965 | class have been implemented for each of the above six |
---|
1966 | processes: |
---|
1967 | |
---|
1968 | <itemizedlist spacing="compact"> |
---|
1969 | <listitem><para> |
---|
1970 | <para> |
---|
1971 | <literal>AtRestGetPhysicalInteractionLength( const G4Track&, |
---|
1972 | G4ForceCondition* )</literal> |
---|
1973 | </para> |
---|
1974 | <para> |
---|
1975 | This method returns the time taken before the interaction actually |
---|
1976 | occurs. In all processes listed above, except for muon capture, a |
---|
1977 | value of zero is returned. For the muon capture process the muon |
---|
1978 | capture lifetime is returned. |
---|
1979 | </para> |
---|
1980 | </para></listitem> |
---|
1981 | <listitem><para> |
---|
1982 | <para> |
---|
1983 | <literal>AtRestDoIt( const G4Track&, const G4Step&)</literal> |
---|
1984 | </para> |
---|
1985 | <para> |
---|
1986 | This method generates the secondary particles produced by the |
---|
1987 | process. |
---|
1988 | </para> |
---|
1989 | </para></listitem> |
---|
1990 | <listitem><para> |
---|
1991 | <para> |
---|
1992 | <literal>IsApplicable( const G4ParticleDefinition& )</literal> |
---|
1993 | </para> |
---|
1994 | <para> |
---|
1995 | This method returns the result of a check to see if the process is |
---|
1996 | possible for a given particle. |
---|
1997 | </para> |
---|
1998 | </para></listitem> |
---|
1999 | </itemizedlist> |
---|
2000 | </para> |
---|
2001 | |
---|
2002 | |
---|
2003 | <!-- ******* Bridgehead ******* --> |
---|
2004 | <bridgehead renderas='sect4'> |
---|
2005 | Example of how to use a hadron at rest process |
---|
2006 | </bridgehead> |
---|
2007 | |
---|
2008 | <para> |
---|
2009 | Including a ``hadron at rest'' process for a particle, a pi- for |
---|
2010 | example, into the Geant4 system is straightforward and can be done |
---|
2011 | in the following way: |
---|
2012 | |
---|
2013 | <itemizedlist spacing="compact"> |
---|
2014 | <listitem><para> |
---|
2015 | create a process: |
---|
2016 | <informalexample> |
---|
2017 | <programlisting> |
---|
2018 | theProcess = new G4PionMinusAbsorptionAtRest(); |
---|
2019 | </programlisting> |
---|
2020 | </informalexample> |
---|
2021 | </para></listitem> |
---|
2022 | <listitem><para> |
---|
2023 | register the process with the particle's process manager: |
---|
2024 | <informalexample> |
---|
2025 | <programlisting> |
---|
2026 | theParticleDef = G4PionMinus::PionMinus(); |
---|
2027 | G4ProcessManager* pman = theParticleDef->GetProcessManager(); |
---|
2028 | pman->AddRestProcess( theProcess ); |
---|
2029 | </programlisting> |
---|
2030 | </informalexample> |
---|
2031 | </para></listitem> |
---|
2032 | </itemizedlist> |
---|
2033 | </para> |
---|
2034 | |
---|
2035 | </sect3> |
---|
2036 | |
---|
2037 | <!-- ******************* Section (Level#3) ****************** --> |
---|
2038 | <sect3 id="sect.PhysProc.Had.Flight"> |
---|
2039 | <title> |
---|
2040 | Hadrons in Flight |
---|
2041 | </title> |
---|
2042 | |
---|
2043 | <!-- ******* Bridgehead ******* --> |
---|
2044 | <bridgehead renderas='sect4'> |
---|
2045 | What processes do you need? |
---|
2046 | </bridgehead> |
---|
2047 | |
---|
2048 | <para> |
---|
2049 | For hadrons in motion, there are four physics process classes. |
---|
2050 | <xref linkend="table.PhysProc_1" /> shows each process and the |
---|
2051 | particles for which it is relevant. |
---|
2052 | |
---|
2053 | <table id="table.PhysProc_1"> |
---|
2054 | <title> |
---|
2055 | Hadronic processes and relevant particles. |
---|
2056 | </title> |
---|
2057 | |
---|
2058 | <tgroup cols="2"> |
---|
2059 | <tbody> |
---|
2060 | <row> |
---|
2061 | <entry> |
---|
2062 | <emphasis>G4HadronElasticProcess</emphasis> |
---|
2063 | </entry> |
---|
2064 | <entry> |
---|
2065 | pi+, pi-, K<superscript>+</superscript>, |
---|
2066 | K<superscript>0</superscript><subscript>S</subscript>, |
---|
2067 | K<superscript>0</superscript><subscript>L</subscript>, |
---|
2068 | K<superscript>-</superscript>, |
---|
2069 | p, p-bar, n, n-bar, lambda, lambda-bar, |
---|
2070 | Sigma<superscript>+</superscript>, Sigma<superscript>-</superscript>, |
---|
2071 | Sigma<superscript>+</superscript>-bar, |
---|
2072 | Sigma<superscript>-</superscript>-bar, |
---|
2073 | Xi<superscript>0</superscript>, Xi<superscript>-</superscript>, |
---|
2074 | Xi<superscript>0</superscript>-bar, Xi<superscript>-</superscript>-bar |
---|
2075 | </entry> |
---|
2076 | </row> |
---|
2077 | <row> |
---|
2078 | <entry> |
---|
2079 | <emphasis>G4HadronInelasticProcess</emphasis> |
---|
2080 | </entry> |
---|
2081 | <entry> |
---|
2082 | pi+, pi-, K<superscript>+</superscript>, |
---|
2083 | K<superscript>0</superscript><subscript>S</subscript>, |
---|
2084 | K<superscript>0</superscript><subscript>L</subscript>, |
---|
2085 | K<superscript>-</superscript>, |
---|
2086 | p, p-bar, n, n-bar, lambda, lambda-bar, |
---|
2087 | Sigma<superscript>+</superscript>, Sigma<superscript>-</superscript>, |
---|
2088 | Sigma<superscript>+</superscript>-bar, |
---|
2089 | Sigma<superscript>-</superscript>-bar, Xi<superscript>0</superscript>, |
---|
2090 | Xi<superscript>-</superscript>, Xi<superscript>0</superscript>-bar, |
---|
2091 | Xi<superscript>-</superscript>-bar |
---|
2092 | </entry> |
---|
2093 | </row> |
---|
2094 | <row> |
---|
2095 | <entry> |
---|
2096 | <emphasis>G4HadronFissionProcess</emphasis> |
---|
2097 | </entry> |
---|
2098 | <entry> |
---|
2099 | all |
---|
2100 | </entry> |
---|
2101 | </row> |
---|
2102 | <row> |
---|
2103 | <entry> |
---|
2104 | <emphasis>G4CaptureProcess</emphasis> |
---|
2105 | </entry> |
---|
2106 | <entry> |
---|
2107 | n, n-bar |
---|
2108 | </entry> |
---|
2109 | </row> |
---|
2110 | </tbody> |
---|
2111 | </tgroup> |
---|
2112 | </table> |
---|
2113 | </para> |
---|
2114 | |
---|
2115 | <!-- ******* Bridgehead ******* --> |
---|
2116 | <bridgehead renderas='sect4'> |
---|
2117 | How to register Models |
---|
2118 | </bridgehead> |
---|
2119 | |
---|
2120 | <para> |
---|
2121 | To register an inelastic process model for a particle, a proton |
---|
2122 | for example, first get the pointer to the particle's process |
---|
2123 | manager: |
---|
2124 | |
---|
2125 | <informalexample> |
---|
2126 | <programlisting> |
---|
2127 | G4ParticleDefinition *theProton = G4Proton::ProtonDefinition(); |
---|
2128 | G4ProcessManager *theProtonProcMan = theProton->GetProcessManager(); |
---|
2129 | </programlisting> |
---|
2130 | </informalexample> |
---|
2131 | </para> |
---|
2132 | |
---|
2133 | <para> |
---|
2134 | Create an instance of the particle's inelastic process: |
---|
2135 | |
---|
2136 | <informalexample> |
---|
2137 | <programlisting> |
---|
2138 | G4ProtonInelasticProcess *theProtonIEProc = new G4ProtonInelasticProcess(); |
---|
2139 | </programlisting> |
---|
2140 | </informalexample> |
---|
2141 | </para> |
---|
2142 | |
---|
2143 | <para> |
---|
2144 | Create an instance of the model which determines the secondaries |
---|
2145 | produced in the interaction, and calculates the momenta of the |
---|
2146 | particles: |
---|
2147 | |
---|
2148 | <informalexample> |
---|
2149 | <programlisting> |
---|
2150 | G4LEProtonInelastic *theProtonIE = new G4LEProtonInelastic(); |
---|
2151 | </programlisting> |
---|
2152 | </informalexample> |
---|
2153 | </para> |
---|
2154 | |
---|
2155 | <para> |
---|
2156 | Register the model with the particle's inelastic process: |
---|
2157 | |
---|
2158 | <informalexample> |
---|
2159 | <programlisting> |
---|
2160 | theProtonIEProc->RegisterMe( theProtonIE ); |
---|
2161 | </programlisting> |
---|
2162 | </informalexample> |
---|
2163 | </para> |
---|
2164 | |
---|
2165 | <para> |
---|
2166 | Finally, add the particle's inelastic process to the list of |
---|
2167 | discrete processes: |
---|
2168 | |
---|
2169 | <informalexample> |
---|
2170 | <programlisting> |
---|
2171 | theProtonProcMan->AddDiscreteProcess( theProtonIEProc ); |
---|
2172 | </programlisting> |
---|
2173 | </informalexample> |
---|
2174 | </para> |
---|
2175 | |
---|
2176 | <para> |
---|
2177 | The particle's inelastic process class, |
---|
2178 | <emphasis>G4ProtonInelasticProcess</emphasis> in the example above, derives from |
---|
2179 | the <emphasis>G4HadronicInelasticProcess</emphasis> class, and simply defines the |
---|
2180 | process name and calls the <emphasis>G4HadronicInelasticProcess</emphasis> |
---|
2181 | constructor. All of the specific particle inelastic processes |
---|
2182 | derive from the <emphasis>G4HadronicInelasticProcess</emphasis> class, which |
---|
2183 | calls the <literal>PostStepDoIt</literal> function, which returns the |
---|
2184 | particle change object from the <emphasis>G4HadronicProcess</emphasis> function |
---|
2185 | <literal>GeneralPostStepDoIt</literal>. This class also gets the mean free |
---|
2186 | path, builds the physics table, and gets the microscopic cross |
---|
2187 | section. The <emphasis>G4HadronicInelasticProcess</emphasis> class derives from |
---|
2188 | the <emphasis>G4HadronicProcess</emphasis> class, which is the top level hadronic |
---|
2189 | process class. The <emphasis>G4HadronicProcess</emphasis> class derives from the |
---|
2190 | <emphasis>G4VDiscreteProcess</emphasis> class. The inelastic, elastic, capture, |
---|
2191 | and fission processes derive from the <emphasis>G4HadronicProcess</emphasis> |
---|
2192 | class. This pure virtual class also provides the energy range |
---|
2193 | manager object and the <literal>RegisterMe</literal> access function. |
---|
2194 | </para> |
---|
2195 | |
---|
2196 | <para> |
---|
2197 | A sample case for the proton's inelastic interaction model class |
---|
2198 | is shown in <xref linkend="programlist_PhysProc_3" />, where |
---|
2199 | <literal>G4LEProtonInelastic.hh</literal> is the name of the include |
---|
2200 | file: |
---|
2201 | |
---|
2202 | <example id="programlist_PhysProc_3"> |
---|
2203 | <title> |
---|
2204 | An example of a proton inelastic interaction model class. |
---|
2205 | </title> |
---|
2206 | |
---|
2207 | <programlisting> |
---|
2208 | ----------------------------- include file ------------------------------------------ |
---|
2209 | |
---|
2210 | #include "G4InelasticInteraction.hh" |
---|
2211 | class G4LEProtonInelastic : public G4InelasticInteraction |
---|
2212 | { |
---|
2213 | public: |
---|
2214 | G4LEProtonInelastic() : G4InelasticInteraction() |
---|
2215 | { |
---|
2216 | SetMinEnergy( 0.0 ); |
---|
2217 | SetMaxEnergy( 25.*GeV ); |
---|
2218 | } |
---|
2219 | ~G4LEProtonInelastic() { } |
---|
2220 | G4ParticleChange *ApplyYourself( const G4Track &aTrack, |
---|
2221 | G4Nucleus &targetNucleus ); |
---|
2222 | private: |
---|
2223 | void CascadeAndCalculateMomenta( required arguments ); |
---|
2224 | }; |
---|
2225 | |
---|
2226 | ----------------------------- source file ------------------------------------------ |
---|
2227 | |
---|
2228 | #include "G4LEProtonInelastic.hh" |
---|
2229 | G4ParticleChange * |
---|
2230 | G4LEProton Inelastic::ApplyYourself( const G4Track &aTrack, |
---|
2231 | G4Nucleus &targetNucleus ) |
---|
2232 | { |
---|
2233 | theParticleChange.Initialize( aTrack ); |
---|
2234 | const G4DynamicParticle *incidentParticle = aTrack.GetDynamicParticle(); |
---|
2235 | // create the target particle |
---|
2236 | G4DynamicParticle *targetParticle = targetNucleus.ReturnTargetParticle(); |
---|
2237 | CascadeAndCalculateMomenta( required arguments ) |
---|
2238 | { ... } |
---|
2239 | return &theParticleChange; |
---|
2240 | } |
---|
2241 | </programlisting> |
---|
2242 | </example> |
---|
2243 | </para> |
---|
2244 | |
---|
2245 | <para> |
---|
2246 | The <literal>CascadeAndCalculateMomenta</literal> function is the bulk of |
---|
2247 | the model and is to be provided by the model's creator. It should |
---|
2248 | determine what secondary particles are produced in the interaction, |
---|
2249 | calculate the momenta for all the particles, and put this |
---|
2250 | information into the <emphasis>ParticleChange</emphasis> object which is |
---|
2251 | returned. |
---|
2252 | </para> |
---|
2253 | |
---|
2254 | <para> |
---|
2255 | The <emphasis>G4LEProtonInelastic</emphasis> class derives from the |
---|
2256 | <emphasis>G4InelasticInteraction</emphasis> class, which is an abstract base |
---|
2257 | class since the pure virtual function <literal>ApplyYourself</literal> is not |
---|
2258 | defined there. <emphasis>G4InelasticInteraction</emphasis> itself derives from |
---|
2259 | the <emphasis>G4HadronicInteraction</emphasis> abstract base class. This class is |
---|
2260 | the base class for all the model classes. It sorts out the energy |
---|
2261 | range for the models and provides class utilities. The |
---|
2262 | <emphasis>G4HadronicInteraction</emphasis> class provides the |
---|
2263 | <literal>Set/GetMinEnergy</literal> and the <literal>Set/GetMaxEnergy</literal> |
---|
2264 | functions which determine the minimum and maximum energy range for |
---|
2265 | the model. An energy range can be set for a specific element, a |
---|
2266 | specific material, or for general applicability: |
---|
2267 | |
---|
2268 | <informalexample> |
---|
2269 | <programlisting> |
---|
2270 | void SetMinEnergy( G4double anEnergy, G4Element *anElement ) |
---|
2271 | void SetMinEnergy( G4double anEnergy, G4Material *aMaterial ) |
---|
2272 | void SetMinEnergy( const G4double anEnergy ) |
---|
2273 | void SetMaxEnergy( G4double anEnergy, G4Element *anElement ) |
---|
2274 | void SetMaxEnergy( G4double anEnergy, G4Material *aMaterial ) |
---|
2275 | void SetMaxEnergy( const G4double anEnergy ) |
---|
2276 | </programlisting> |
---|
2277 | </informalexample> |
---|
2278 | </para> |
---|
2279 | |
---|
2280 | <!-- ******* Bridgehead ******* --> |
---|
2281 | <bridgehead renderas='sect4'> |
---|
2282 | Which models are there, and what are the defaults |
---|
2283 | </bridgehead> |
---|
2284 | |
---|
2285 | <para> |
---|
2286 | In Geant4, any model can be run together with any other model |
---|
2287 | without the need for the implementation of a special interface, or |
---|
2288 | batch suite, and the ranges of applicability for the different |
---|
2289 | models can be steered at initialisation time. This way, highly |
---|
2290 | specialised models (valid only for one material and particle, and |
---|
2291 | applicable only in a very restricted energy range) can be used in |
---|
2292 | the same application, together with more general code, in a |
---|
2293 | coherent fashion. |
---|
2294 | </para> |
---|
2295 | |
---|
2296 | <para> |
---|
2297 | Each model has an intrinsic range of applicability, and the |
---|
2298 | model chosen for a simulation depends very much on the use-case. |
---|
2299 | Consequently, there are no ``defaults''. However, physics lists are |
---|
2300 | provided which specify sets of models for various purposes. |
---|
2301 | </para> |
---|
2302 | |
---|
2303 | <para> |
---|
2304 | Three types of hadronic shower models have been implemented: |
---|
2305 | parametrisation driven models, data driven models, and theory |
---|
2306 | driven models. |
---|
2307 | |
---|
2308 | <itemizedlist spacing="compact"> |
---|
2309 | <listitem><para> |
---|
2310 | Parametrisation driven models are used for all processes |
---|
2311 | pertaining to particles coming to rest, and interacting with the |
---|
2312 | nucleus. For particles in flight, two sets of models exist for |
---|
2313 | inelastic scattering; low energy, and high energy models. Both sets |
---|
2314 | are based originally on the <emphasis role="bold">GHEISHA</emphasis> |
---|
2315 | package of Geant3.21, |
---|
2316 | and the original approaches to primary interaction, nuclear |
---|
2317 | excitation, intra-nuclear cascade and evaporation is kept. The |
---|
2318 | models are located in the sub-directories |
---|
2319 | <literal>hadronics/models/low_energy</literal> and |
---|
2320 | <literal>hadronics/models/high_energy</literal>. The low energy models are |
---|
2321 | targeted towards energies below 20 GeV; the high energy models |
---|
2322 | cover the energy range from 20 GeV to O(TeV). Fission, capture and |
---|
2323 | coherent elastic scattering are also modeled through parametrised |
---|
2324 | models. |
---|
2325 | </para></listitem> |
---|
2326 | <listitem><para> |
---|
2327 | Data driven models are available for the transport of low |
---|
2328 | energy neutrons in matter in sub-directory |
---|
2329 | <literal>hadronics/models/neutron_hp</literal>. The modeling is based |
---|
2330 | on the data formats of <emphasis role="bold">ENDF/B-VI</emphasis>, |
---|
2331 | and all distributions of this standard data format are implemented. |
---|
2332 | The data sets used are selected from data libraries that conform to |
---|
2333 | these standard formats. The file system is used in order to allow granular |
---|
2334 | access to, and flexibility in, the use of the cross sections for different |
---|
2335 | isotopes, and channels. The energy coverage of these models is from |
---|
2336 | thermal energies to 20 MeV. |
---|
2337 | </para></listitem> |
---|
2338 | <listitem><para> |
---|
2339 | Theory driven models are available for inelastic scattering in |
---|
2340 | a first implementation, covering the full energy range of LHC |
---|
2341 | experiments. They are located in sub-directory |
---|
2342 | <literal>hadronics/models/generator</literal>. The current philosophy |
---|
2343 | implies the usage of parton string models at high energies, of |
---|
2344 | intra-nuclear transport models at intermediate energies, and of |
---|
2345 | statistical break-up models for de-excitation. |
---|
2346 | </para></listitem> |
---|
2347 | </itemizedlist> |
---|
2348 | </para> |
---|
2349 | |
---|
2350 | </sect3> |
---|
2351 | </sect2> |
---|
2352 | |
---|
2353 | <!-- ******************* Section (Level#2) ****************** --> |
---|
2354 | <sect2 id="sect.PhysProc.Decay"> |
---|
2355 | <title> |
---|
2356 | Particle Decay Process |
---|
2357 | </title> |
---|
2358 | |
---|
2359 | <para> |
---|
2360 | This section briefly introduces decay processes installed in |
---|
2361 | Geant4. For details of the implementation of particle decays, |
---|
2362 | please refer to the |
---|
2363 | <ulink url="http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/PhysicsReferenceManual/html/PhysicsReferenceManual.html"> |
---|
2364 | <emphasis role="bold">Physics Reference Manual</emphasis></ulink>. |
---|
2365 | </para> |
---|
2366 | |
---|
2367 | <!-- ******************* Section (Level#3) ****************** --> |
---|
2368 | <sect3 id="sect.PhysProc.Decay.Class"> |
---|
2369 | <title> |
---|
2370 | Particle Decay Class |
---|
2371 | </title> |
---|
2372 | |
---|
2373 | <para> |
---|
2374 | Geant4 provides a <emphasis>G4Decay</emphasis> class for both ``at rest'' and |
---|
2375 | ``in flight'' particle decays. <emphasis>G4Decay</emphasis> can be applied to all |
---|
2376 | particles except: |
---|
2377 | |
---|
2378 | <variablelist> |
---|
2379 | <varlistentry> |
---|
2380 | <term> |
---|
2381 | massless particles, i.e., |
---|
2382 | </term> |
---|
2383 | <listitem> |
---|
2384 | <literal>G4ParticleDefinition::thePDGMass <= 0</literal> |
---|
2385 | </listitem> |
---|
2386 | </varlistentry> |
---|
2387 | <varlistentry> |
---|
2388 | <term> |
---|
2389 | particles with ``negative'' life time, i.e., |
---|
2390 | </term> |
---|
2391 | <listitem> |
---|
2392 | <literal>G4ParticleDefinition::thePDGLifeTime < 0</literal> |
---|
2393 | </listitem> |
---|
2394 | </varlistentry> |
---|
2395 | <varlistentry> |
---|
2396 | <term> |
---|
2397 | shortlived particles, i.e., |
---|
2398 | </term> |
---|
2399 | <listitem> |
---|
2400 | <literal>G4ParticleDefinition::fShortLivedFlag = True</literal> |
---|
2401 | </listitem> |
---|
2402 | </varlistentry> |
---|
2403 | </variablelist> |
---|
2404 | </para> |
---|
2405 | |
---|
2406 | <para> |
---|
2407 | Decay for some particles may be switched on or off by using |
---|
2408 | <literal>G4ParticleDefinition::SetPDGStable()</literal> as well as |
---|
2409 | <literal>ActivateProcess()</literal> and <literal>InActivateProcess()</literal> |
---|
2410 | methods of <emphasis>G4ProcessManager</emphasis>. |
---|
2411 | </para> |
---|
2412 | |
---|
2413 | <para> |
---|
2414 | <emphasis>G4Decay</emphasis> proposes the step length (or step time for |
---|
2415 | <literal>AtRest</literal>) according to the lifetime of the particle unless |
---|
2416 | <literal>PreAssignedDecayProperTime</literal> is defined in |
---|
2417 | <emphasis>G4DynamicParticle</emphasis>. |
---|
2418 | </para> |
---|
2419 | |
---|
2420 | <para> |
---|
2421 | The <emphasis>G4Decay</emphasis> class itself does not define decay modes of |
---|
2422 | the particle. Geant4 provides two ways of doing this: |
---|
2423 | |
---|
2424 | <itemizedlist spacing="compact"> |
---|
2425 | <listitem><para> |
---|
2426 | using <emphasis>G4DecayChannel</emphasis> in <emphasis>G4DecayTable</emphasis>, |
---|
2427 | and |
---|
2428 | </para></listitem> |
---|
2429 | <listitem><para> |
---|
2430 | using <literal>thePreAssignedDecayProducts</literal> of |
---|
2431 | <emphasis>G4DynamicParticle</emphasis> |
---|
2432 | </para></listitem> |
---|
2433 | </itemizedlist> |
---|
2434 | </para> |
---|
2435 | |
---|
2436 | <para> |
---|
2437 | The <emphasis>G4Decay</emphasis> class calculates the |
---|
2438 | <literal>PhysicalInteractionLength</literal> and boosts decay products |
---|
2439 | created by <emphasis>G4VDecayChannel</emphasis> or event generators. See below |
---|
2440 | for information on the determination of the decay modes. |
---|
2441 | </para> |
---|
2442 | |
---|
2443 | <para> |
---|
2444 | An object of <emphasis>G4Decay</emphasis> can be shared by particles. |
---|
2445 | Registration of the decay process to particles in the |
---|
2446 | <literal>ConstructPhysics</literal> method of <emphasis>PhysicsList</emphasis> |
---|
2447 | (see <xref linkend="sect.HowToSpecPhysProc.SpecPhysProc" />) |
---|
2448 | is shown in <xref linkend="programlist_PhysProc_4" />. |
---|
2449 | |
---|
2450 | <example id="programlist_PhysProc_4"> |
---|
2451 | <title> |
---|
2452 | Registration of the decay process to particles in the |
---|
2453 | <literal>ConstructPhysics</literal> method of <emphasis>PhysicsList</emphasis>. |
---|
2454 | </title> |
---|
2455 | |
---|
2456 | <programlisting> |
---|
2457 | #include "G4Decay.hh" |
---|
2458 | void ExN02PhysicsList::ConstructGeneral() |
---|
2459 | { |
---|
2460 | // Add Decay Process |
---|
2461 | G4Decay* theDecayProcess = new G4Decay(); |
---|
2462 | theParticleIterator->reset(); |
---|
2463 | while( (*theParticleIterator)() ){ |
---|
2464 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
2465 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
2466 | if (theDecayProcess->IsApplicable(*particle)) { |
---|
2467 | pmanager ->AddProcess(theDecayProcess); |
---|
2468 | // set ordering for PostStepDoIt and AtRestDoIt |
---|
2469 | pmanager ->SetProcessOrdering(theDecayProcess, idxPostStep); |
---|
2470 | pmanager ->SetProcessOrdering(theDecayProcess, idxAtRest); |
---|
2471 | } |
---|
2472 | } |
---|
2473 | } |
---|
2474 | </programlisting> |
---|
2475 | </example> |
---|
2476 | </para> |
---|
2477 | |
---|
2478 | </sect3> |
---|
2479 | |
---|
2480 | <!-- ******************* Section (Level#3) ****************** --> |
---|
2481 | <sect3 id="sect.PhysProc.Decay.Table"> |
---|
2482 | <title> |
---|
2483 | Decay Table |
---|
2484 | </title> |
---|
2485 | |
---|
2486 | <para> |
---|
2487 | Each particle has its <emphasis>G4DecayTable</emphasis>, which stores information |
---|
2488 | on the decay modes of the particle. Each decay mode, with its |
---|
2489 | branching ratio, corresponds to an object of various ``decay |
---|
2490 | channel'' classes derived from <emphasis>G4VDecayChannel</emphasis>. Default |
---|
2491 | decay modes are created in the constructors of particle classes. |
---|
2492 | For example, the decay table of the neutral pion has |
---|
2493 | <emphasis>G4PhaseSpaceDecayChannel</emphasis> and |
---|
2494 | <emphasis>G4DalitzDecayChannel</emphasis> as follows: |
---|
2495 | |
---|
2496 | <informalexample> |
---|
2497 | <programlisting> |
---|
2498 | // create a decay channel |
---|
2499 | G4VDecayChannel* mode; |
---|
2500 | // pi0 -> gamma + gamma |
---|
2501 | mode = new G4PhaseSpaceDecayChannel("pi0",0.988,2,"gamma","gamma"); |
---|
2502 | table->Insert(mode); |
---|
2503 | // pi0 -> gamma + e+ + e- |
---|
2504 | mode = new G4DalitzDecayChannel("pi0",0.012,"e-","e+"); |
---|
2505 | table->Insert(mode); |
---|
2506 | </programlisting> |
---|
2507 | </informalexample> |
---|
2508 | </para> |
---|
2509 | |
---|
2510 | <para> |
---|
2511 | Decay modes and branching ratios defined in Geant4 are listed in |
---|
2512 | <xref linkend="sect.Parti.Def" />. |
---|
2513 | </para> |
---|
2514 | |
---|
2515 | <para> |
---|
2516 | Branching ratios and life time can be set in tracking time. |
---|
2517 | <informalexample> |
---|
2518 | <programlisting> |
---|
2519 | // set lifetime |
---|
2520 | G4Neutron::Neutron()->SetPDGLifeTime(885.7*second); |
---|
2521 | // allow neutron decay |
---|
2522 | G4Neutron::Neutron()->SetPDGStable(false); |
---|
2523 | </programlisting> |
---|
2524 | </informalexample> |
---|
2525 | </para> |
---|
2526 | |
---|
2527 | <para> |
---|
2528 | Branching ratios and life time can be modified by using user commands, also. |
---|
2529 | </para> |
---|
2530 | |
---|
2531 | <para> |
---|
2532 | <emphasis role="bold">Example: Set 100% br for dalitz decay of pi0</emphasis> |
---|
2533 | |
---|
2534 | <informalexample> |
---|
2535 | <programlisting> |
---|
2536 | Idle> /particle/select pi0 |
---|
2537 | Idle> /particle/property/decay/select 0 |
---|
2538 | Idle> /particle/property/decay/br 0 |
---|
2539 | Idle> /particle/property/decay/select 1 |
---|
2540 | Idle> /particle/property/decay/br 1 |
---|
2541 | Idle> /particle/property/decay/dump |
---|
2542 | G4DecayTable: pi0 |
---|
2543 | 0: BR: 0 [Phase Space] : gamma gamma |
---|
2544 | 1: BR: 1 [Dalitz Decay] : gamma e- e+ |
---|
2545 | </programlisting> |
---|
2546 | </informalexample> |
---|
2547 | |
---|
2548 | </para> |
---|
2549 | |
---|
2550 | </sect3> |
---|
2551 | |
---|
2552 | <!-- ******************* Section (Level#3) ****************** --> |
---|
2553 | <sect3 id="sect.PhysProc.Decay.PreAssgn"> |
---|
2554 | <title> |
---|
2555 | Pre-assigned Decay Modes by Event Generators |
---|
2556 | </title> |
---|
2557 | |
---|
2558 | <para> |
---|
2559 | Decays of heavy flavor particles such as B mesons are very complex, |
---|
2560 | with many varieties of decay modes and decay mechanisms. There are |
---|
2561 | many models for heavy particle decay provided by various event |
---|
2562 | generators and it is impossible to define all the decay modes of |
---|
2563 | heavy particles by using <emphasis>G4VDecayChannel</emphasis>. In other words, |
---|
2564 | decays of heavy particles cannot be defined by the Geant4 decay |
---|
2565 | process, but should be defined by event generators or other |
---|
2566 | external packages. Geant4 provides two ways to do this: |
---|
2567 | <literal>pre-assigned decay mode</literal> and <literal>external decayer</literal>. |
---|
2568 | </para> |
---|
2569 | |
---|
2570 | <para> |
---|
2571 | In the latter approach, the class <emphasis>G4VExtDecayer</emphasis> is used |
---|
2572 | for the interface to an external package which defines decay modes |
---|
2573 | for a particle. If an instance of <emphasis>G4VExtDecayer</emphasis> is attached |
---|
2574 | to <emphasis>G4Decay</emphasis>, daughter particles will be generated by the |
---|
2575 | external decay handler. |
---|
2576 | </para> |
---|
2577 | |
---|
2578 | <para> |
---|
2579 | In the former case, decays of heavy particles are simulated by |
---|
2580 | an event generator and the primary event contains the decay |
---|
2581 | information. <emphasis>G4VPrimaryGenerator</emphasis> automatically attaches any |
---|
2582 | daughter particles to the parent particle as the |
---|
2583 | PreAssignedDecayProducts member of <emphasis>G4DynamicParticle</emphasis>. |
---|
2584 | <emphasis>G4Decay</emphasis> adopts these pre-assigned daughter particles instead |
---|
2585 | of asking <emphasis>G4VDecayChannel</emphasis> to generate decay products. |
---|
2586 | </para> |
---|
2587 | |
---|
2588 | <para> |
---|
2589 | In addition, the user may assign a <literal>pre-assigned</literal> decay |
---|
2590 | time for a specific track in its rest frame (i.e. decay time is |
---|
2591 | defined in the proper time) by using the |
---|
2592 | <emphasis>G4PrimaryParticle::SetProperTime()</emphasis> method. |
---|
2593 | <emphasis>G4VPrimaryGenerator</emphasis> sets the PreAssignedDecayProperTime |
---|
2594 | member of <emphasis>G4DynamicParticle</emphasis>. <emphasis>G4Decay</emphasis> |
---|
2595 | uses this decay time instead of the life time of the particle type. |
---|
2596 | </para> |
---|
2597 | |
---|
2598 | </sect3> |
---|
2599 | </sect2> |
---|
2600 | |
---|
2601 | |
---|
2602 | <!-- ******************* Section (Level#2) ****************** --> |
---|
2603 | <sect2 id="sect.PhysProc.PhotoHad"> |
---|
2604 | <title> |
---|
2605 | Photolepton-hadron Processes |
---|
2606 | </title> |
---|
2607 | |
---|
2608 | <para> |
---|
2609 | To be delivered. |
---|
2610 | </para> |
---|
2611 | |
---|
2612 | </sect2> |
---|
2613 | |
---|
2614 | |
---|
2615 | <!-- ******************* Section (Level#2) ****************** --> |
---|
2616 | <sect2 id="sect.PhysProc.Photo"> |
---|
2617 | <title> |
---|
2618 | Optical Photon Processes |
---|
2619 | </title> |
---|
2620 | |
---|
2621 | <para> |
---|
2622 | A photon is considered to be <emphasis>optical</emphasis> when its wavelength |
---|
2623 | is much greater than the typical atomic spacing. In GEANT4 optical |
---|
2624 | photons are treated as a class of particle distinct from their |
---|
2625 | higher energy <emphasis>gamma</emphasis> cousins. This implementation allows the |
---|
2626 | wave-like properties of electromagnetic radiation to be |
---|
2627 | incorporated into the optical photon process. Because this |
---|
2628 | theoretical description breaks down at higher energies, there is no |
---|
2629 | smooth transition as a function of energy between the optical |
---|
2630 | photon and gamma particle classes. |
---|
2631 | </para> |
---|
2632 | |
---|
2633 | <para> |
---|
2634 | For the simulation of optical photons to work correctly in |
---|
2635 | GEANT4, they must be imputed a linear polarization. This is unlike |
---|
2636 | most other particles in GEANT4 but is automatically and correctly |
---|
2637 | done for optical photons that are generated as secondaries by |
---|
2638 | existing processes in GEANT4. Not so, if the user wishes to start |
---|
2639 | optical photons as primary particles. In this case, the user must |
---|
2640 | set the linear polarization using particle gun methods, the General |
---|
2641 | Particle Source, or his/her PrimaryGeneratorAction. For an |
---|
2642 | unpolarized source, the linear polarization should be sampled |
---|
2643 | randomly for each new primary photon. |
---|
2644 | </para> |
---|
2645 | |
---|
2646 | <para> |
---|
2647 | The GEANT4 catalogue of processes at optical wavelengths |
---|
2648 | includes refraction and reflection at medium boundaries, bulk |
---|
2649 | absorption and Rayleigh scattering. Processes which produce optical |
---|
2650 | photons include the Cerenkov effect, transition radiation and |
---|
2651 | scintillation. Optical photons are generated in GEANT4 without |
---|
2652 | energy conservation and their energy must therefore not be tallied |
---|
2653 | as part of the energy balance of an event. |
---|
2654 | </para> |
---|
2655 | |
---|
2656 | <para> |
---|
2657 | The optical properties of the medium which are key to the |
---|
2658 | implementation of these types of processes are stored as entries in |
---|
2659 | a <literal>G4MaterialPropertiesTable</literal> which is linked to the |
---|
2660 | <literal>G4Material</literal> in question. These properties may be constants |
---|
2661 | or they may be expressed as a function of the photon's wavelength. |
---|
2662 | This table is a private data member of the <literal>G4Material</literal> |
---|
2663 | class. The <literal>G4MaterialPropertiesTable</literal> is implemented as a |
---|
2664 | hash directory, in which each entry consists of a <emphasis>value</emphasis> and |
---|
2665 | a <emphasis>key</emphasis>. The key is used to quickly and efficiently retrieve |
---|
2666 | the corresponding value. All values in the dictionary are either |
---|
2667 | instantiations of <literal>G4double</literal> or the class |
---|
2668 | <literal>G4MaterialPropertyVector</literal>, and all keys are of type |
---|
2669 | <literal>G4String</literal>. |
---|
2670 | </para> |
---|
2671 | |
---|
2672 | <para> |
---|
2673 | A <literal>G4MaterialPropertyVector</literal> is composed of |
---|
2674 | instantiations of the class <literal>G4MPVEntry</literal>. The |
---|
2675 | <literal>G4MPVEntry</literal> is a pair of numbers, which in the case of an |
---|
2676 | optical property, are the photon momentum and corresponding |
---|
2677 | property value. The <literal>G4MaterialPropertyVector</literal> is |
---|
2678 | implemented as a <literal>G4std::vector</literal>, with the sorting operation |
---|
2679 | defined as |
---|
2680 | MPVEntry<subscript>1</subscript> < MPVEntry<subscript>2</subscript> == |
---|
2681 | photon_momentum<subscript>1</subscript> < photon_momentum<subscript>2</subscript>. |
---|
2682 | This results in all <literal>G4MaterialPropertyVector</literal>s being sorted in |
---|
2683 | ascending order of photon momenta. It is possible for the user to |
---|
2684 | add as many material (optical) properties to the material as he |
---|
2685 | wishes using the methods supplied by the |
---|
2686 | <literal>G4MaterialPropertiesTable</literal> class. An example of this is |
---|
2687 | shown in <xref linkend="programlist_PhysProc_5" />. |
---|
2688 | |
---|
2689 | <example id="programlist_PhysProc_5"> |
---|
2690 | <title> |
---|
2691 | Optical properties added to a <literal>G4MaterialPropertiesTable</literal> |
---|
2692 | and linked to a <literal>G4Material</literal> |
---|
2693 | </title> |
---|
2694 | |
---|
2695 | <programlisting> |
---|
2696 | const G4int NUMENTRIES = 32; |
---|
2697 | |
---|
2698 | G4double ppckov[NUMENTRIES] = {2.034*eV, ......, 4.136*eV}; |
---|
2699 | G4double rindex[NUMENTRIES] = {1.3435, ......, 1.3608}; |
---|
2700 | G4double absorption[NUMENTRIES] = {344.8*cm, ......, 1450.0*cm]; |
---|
2701 | |
---|
2702 | G4MaterialPropertiesTable *MPT = new G4MaterialPropertiesTable(); |
---|
2703 | |
---|
2704 | MPT -> AddConstProperty("SCINTILLATIONYIELD",100./MeV); |
---|
2705 | |
---|
2706 | MPT -> AddProperty("RINDEX",ppckov,rindex,NUMENTRIES}; |
---|
2707 | MPT -> AddProperty("ABSLENGTH",ppckov,absorption,NUMENTRIES}; |
---|
2708 | |
---|
2709 | scintillator -> SetMaterialPropertiesTable(MPT); |
---|
2710 | </programlisting> |
---|
2711 | </example> |
---|
2712 | </para> |
---|
2713 | |
---|
2714 | |
---|
2715 | <!-- ******************* Section (Level#3) ****************** --> |
---|
2716 | <sect3 id="sect.PhysProc.Photo.Cerenkov"> |
---|
2717 | <title> |
---|
2718 | Generation of Photons in |
---|
2719 | <literal>processes/electromagnetic/xrays</literal> - Cerenkov Effect |
---|
2720 | </title> |
---|
2721 | |
---|
2722 | <para> |
---|
2723 | The radiation of Cerenkov light occurs when a charged particle |
---|
2724 | moves through a dispersive medium faster than the group velocity of |
---|
2725 | light in that medium. Photons are emitted on the surface of a cone, |
---|
2726 | whose opening angle with respect to the particle's instantaneous |
---|
2727 | direction decreases as the particle slows down. At the same time, |
---|
2728 | the frequency of the photons emitted increases, and the number |
---|
2729 | produced decreases. When the particle velocity drops below the |
---|
2730 | local speed of light, the radiation ceases and the emission cone |
---|
2731 | angle collapses to zero. The photons produced by this process have |
---|
2732 | an inherent polarization perpendicular to the cone's surface at |
---|
2733 | production. |
---|
2734 | </para> |
---|
2735 | |
---|
2736 | <para> |
---|
2737 | The flux, spectrum, polarization and emission of Cerenkov |
---|
2738 | radiation in the <literal>AlongStepDoIt</literal> method of the class |
---|
2739 | <literal>G4Cerenkov</literal> follow well-known formulae, with two inherent |
---|
2740 | computational limitations. The first arises from step-wise |
---|
2741 | simulation, and the second comes from the requirement that |
---|
2742 | numerical integration calculate the average number of Cerenkov |
---|
2743 | photons per step. The process makes use of a |
---|
2744 | <literal>G4PhysicsTable</literal> which contains incremental integrals to |
---|
2745 | expedite this calculation. |
---|
2746 | </para> |
---|
2747 | |
---|
2748 | <para> |
---|
2749 | The time and position of Cerenkov photon emission are calculated |
---|
2750 | from quantities known at the beginning of a charged particle's |
---|
2751 | step. The step is assumed to be rectilinear even in the presence of |
---|
2752 | a magnetic field. The user may limit the step size by specifying a |
---|
2753 | maximum (average) number of Cerenkov photons created during the |
---|
2754 | step, using the <literal>SetMaxNumPhotonsPerStep(const G4int |
---|
2755 | NumPhotons)</literal> method. The actual number generated will |
---|
2756 | necessarily be different due to the Poissonian nature of the |
---|
2757 | production. In the present implementation, the production density |
---|
2758 | of photons is distributed evenly along the particle's track |
---|
2759 | segment, even if the particle has slowed significantly during the |
---|
2760 | step. |
---|
2761 | </para> |
---|
2762 | |
---|
2763 | <para> |
---|
2764 | The frequently very large number of secondaries produced in a |
---|
2765 | single step (about 300/cm in water), compelled the idea in |
---|
2766 | GEANT3.21 of suspending the primary particle until all its progeny |
---|
2767 | have been tracked. Despite the fact that GEANT4 employs dynamic |
---|
2768 | memory allocation and thus does not suffer from the limitations of |
---|
2769 | GEANT3.21 with its fixed large initial ZEBRA store, GEANT4 |
---|
2770 | nevertheless provides for an analogous functionality with the |
---|
2771 | public method <literal>SetTrackSecondariesFirst</literal>. An example of the |
---|
2772 | registration of the Cerenkov process is given in |
---|
2773 | <xref linkend="programlist_PhysProc_6" />. |
---|
2774 | |
---|
2775 | <example id="programlist_PhysProc_6"> |
---|
2776 | <title> |
---|
2777 | Registration of the Cerenkov process in <literal>PhysicsList</literal>. |
---|
2778 | </title> |
---|
2779 | |
---|
2780 | <programlisting> |
---|
2781 | #include "G4Cerenkov.hh" |
---|
2782 | |
---|
2783 | void ExptPhysicsList::ConstructOp(){ |
---|
2784 | |
---|
2785 | G4Cerenkov* theCerenkovProcess = new G4Cerenkov("Cerenkov"); |
---|
2786 | |
---|
2787 | G4int MaxNumPhotons = 300; |
---|
2788 | |
---|
2789 | theCerenkovProcess->SetTrackSecondariesFirst(true); |
---|
2790 | theCerenkovProcess->SetMaxNumPhotonsPerStep(MaxNumPhotons); |
---|
2791 | |
---|
2792 | theParticleIterator->reset(); |
---|
2793 | while( (*theParticleIterator)() ){ |
---|
2794 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
2795 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
2796 | G4String particleName = particle->GetParticleName(); |
---|
2797 | if (theCerenkovProcess->IsApplicable(*particle)) { |
---|
2798 | pmanager->AddContinuousProcess(theCerenkovProcess); |
---|
2799 | } |
---|
2800 | } |
---|
2801 | } |
---|
2802 | </programlisting> |
---|
2803 | </example> |
---|
2804 | </para> |
---|
2805 | |
---|
2806 | </sect3> |
---|
2807 | |
---|
2808 | |
---|
2809 | <!-- ******************* Section (Level#3) ****************** --> |
---|
2810 | <sect3 id="sect.PhysProc.Photo.Scinti"> |
---|
2811 | <title> |
---|
2812 | Generation of Photons in |
---|
2813 | <literal>processes/electromagnetic/xrays</literal> - Scintillation |
---|
2814 | </title> |
---|
2815 | |
---|
2816 | <para> |
---|
2817 | Every scintillating material has a characteristic light yield, |
---|
2818 | <literal>SCINTILLATIONYIELD</literal>, and an intrinsic resolution, |
---|
2819 | <literal>RESOLUTIONSCALE</literal>, which generally broadens the statistical |
---|
2820 | distribution of generated photons. A wider intrinsic resolution is |
---|
2821 | due to impurities which are typical for doped crystals like NaI(Tl) |
---|
2822 | and CsI(Tl). On the other hand, the intrinsic resolution can also |
---|
2823 | be narrower when the Fano factor plays a role. The actual number of |
---|
2824 | emitted photons during a step fluctuates around the mean number of |
---|
2825 | photons with a width given by |
---|
2826 | <literal>ResolutionScale*sqrt(MeanNumberOfPhotons)</literal>. The average |
---|
2827 | light yield, <literal>MeanNumberOfPhotons</literal>, has a linear dependence |
---|
2828 | on the local energy deposition, but it may be different for minimum |
---|
2829 | ionizing and non-minimum ionizing particles. |
---|
2830 | </para> |
---|
2831 | |
---|
2832 | <para> |
---|
2833 | A scintillator is also characterized by its photon emission |
---|
2834 | spectrum and by the exponential decay of its time spectrum. In |
---|
2835 | GEANT4 the scintillator can have a fast and a slow component. The |
---|
2836 | relative strength of the fast component as a fraction of total |
---|
2837 | scintillation yield is given by the <literal>YIELDRATIO</literal>. |
---|
2838 | Scintillation may be simulated by specifying these empirical |
---|
2839 | parameters for each material. It is sufficient to specify in the |
---|
2840 | user's <literal>DetectorConstruction</literal> class a relative spectral |
---|
2841 | distribution as a function of photon energy for the scintillating |
---|
2842 | material. An example of this is shown in |
---|
2843 | <xref linkend="programlist_PhysProc_7" /> |
---|
2844 | |
---|
2845 | <example id="programlist_PhysProc_7"> |
---|
2846 | <title> |
---|
2847 | Specification of scintillation properties in |
---|
2848 | <literal>DetectorConstruction</literal>. |
---|
2849 | </title> |
---|
2850 | <programlisting> |
---|
2851 | const G4int NUMENTRIES = 9; |
---|
2852 | G4double Scnt_PP[NUMENTRIES] = { 6.6*eV, 6.7*eV, 6.8*eV, 6.9*eV, |
---|
2853 | 7.0*eV, 7.1*eV, 7.2*eV, 7.3*eV, 7.4*eV }; |
---|
2854 | |
---|
2855 | G4double Scnt_FAST[NUMENTRIES] = { 0.000134, 0.004432, 0.053991, 0.241971, |
---|
2856 | 0.398942, 0.000134, 0.004432, 0.053991, |
---|
2857 | 0.241971 }; |
---|
2858 | G4double Scnt_SLOW[NUMENTRIES] = { 0.000010, 0.000020, 0.000030, 0.004000, |
---|
2859 | 0.008000, 0.005000, 0.020000, 0.001000, |
---|
2860 | 0.000010 }; |
---|
2861 | |
---|
2862 | G4Material* Scnt; |
---|
2863 | G4MaterialPropertiesTable* Scnt_MPT = new G4MaterialPropertiesTable(); |
---|
2864 | |
---|
2865 | Scnt_MPT->AddProperty("FASTCOMPONENT", Scnt_PP, Scnt_FAST, NUMENTRIES); |
---|
2866 | Scnt_MPT->AddProperty("SLOWCOMPONENT", Scnt_PP, Scnt_SLOW, NUMENTRIES); |
---|
2867 | |
---|
2868 | Scnt_MPT->AddConstProperty("SCINTILLATIONYIELD", 5000./MeV); |
---|
2869 | Scnt_MPT->AddConstProperty("RESOLUTIONSCALE", 2.0); |
---|
2870 | Scnt_MPT->AddConstProperty("FASTTIMECONSTANT", 1.*ns); |
---|
2871 | Scnt_MPT->AddConstProperty("SLOWTIMECONSTANT", 10.*ns); |
---|
2872 | Scnt_MPT->AddConstProperty("YIELDRATIO", 0.8); |
---|
2873 | |
---|
2874 | Scnt->SetMaterialPropertiesTable(Scnt_MPT); |
---|
2875 | </programlisting> |
---|
2876 | </example> |
---|
2877 | </para> |
---|
2878 | |
---|
2879 | <para> |
---|
2880 | In cases where the scintillation yield of a scintillator depends |
---|
2881 | on the particle type, different scintillation processes may be |
---|
2882 | defined for them. How this yield scales to the one specified for |
---|
2883 | the material is expressed with the |
---|
2884 | <literal>ScintillationYieldFactor</literal> in the user's |
---|
2885 | <literal>PhysicsList</literal> as shown in |
---|
2886 | <xref linkend="programlist_PhysProc_8" />. |
---|
2887 | In those cases where the fast to slow excitation ratio changes with particle |
---|
2888 | type, the method <literal>SetScintillationExcitationRatio</literal> can be |
---|
2889 | called for each scintillation process (see the advanced |
---|
2890 | underground_physics example). This overwrites the |
---|
2891 | <literal>YieldRatio</literal> obtained from the |
---|
2892 | <literal>G4MaterialPropertiesTable</literal>. |
---|
2893 | |
---|
2894 | <example id="programlist_PhysProc_8"> |
---|
2895 | <title> |
---|
2896 | Implementation of the scintillation process in |
---|
2897 | <literal>PhysicsList</literal>. |
---|
2898 | </title> |
---|
2899 | |
---|
2900 | <programlisting> |
---|
2901 | G4Scintillation* theMuonScintProcess = new G4Scintillation("Scintillation"); |
---|
2902 | |
---|
2903 | theMuonScintProcess->SetTrackSecondariesFirst(true); |
---|
2904 | theMuonScintProcess->SetScintillationYieldFactor(0.8); |
---|
2905 | |
---|
2906 | theParticleIterator->reset(); |
---|
2907 | while( (*theParticleIterator)() ){ |
---|
2908 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
2909 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
2910 | G4String particleName = particle->GetParticleName(); |
---|
2911 | if (theMuonScintProcess->IsApplicable(*particle)) { |
---|
2912 | if (particleName == "mu+") { |
---|
2913 | pmanager->AddProcess(theMuonScintProcess); |
---|
2914 | pmanager->SetProcessOrderingToLast(theMuonScintProcess, idxAtRest); |
---|
2915 | pmanager->SetProcessOrderingToLast(theMuonScintProcess, idxPostStep); |
---|
2916 | } |
---|
2917 | } |
---|
2918 | } |
---|
2919 | </programlisting> |
---|
2920 | </example> |
---|
2921 | </para> |
---|
2922 | |
---|
2923 | <para> |
---|
2924 | A Gaussian-distributed number of photons is generated according |
---|
2925 | to the energy lost during the step. A resolution scale of 1.0 |
---|
2926 | produces a statistical fluctuation around the average yield set |
---|
2927 | with <literal>AddConstProperty("SCINTILLATIONYIELD")</literal>, while values |
---|
2928 | > 1 broaden the fluctuation. A value of zero produces no |
---|
2929 | fluctuation. Each photon's frequency is sampled from the empirical |
---|
2930 | spectrum. The photons originate evenly along the track segment and |
---|
2931 | are emitted uniformly into 4π with a random linear polarization |
---|
2932 | and at times characteristic for the scintillation component. |
---|
2933 | </para> |
---|
2934 | |
---|
2935 | </sect3> |
---|
2936 | |
---|
2937 | <!-- ******************* Section (Level#3) ****************** --> |
---|
2938 | <sect3 id="sect.PhysProc.Photo.WaveShift"> |
---|
2939 | <title> |
---|
2940 | Generation of Photons in |
---|
2941 | <literal>processes/optical</literal> - Wavelength Shifting |
---|
2942 | </title> |
---|
2943 | |
---|
2944 | <para> |
---|
2945 | Wavelength Shifting (WLS) fibers are used in many high-energy |
---|
2946 | particle physics experiments. They absorb light at one wavelength |
---|
2947 | and re-emit light at a different wavelength and are used for |
---|
2948 | several reasons. For one, they tend to decrease the self-absorption |
---|
2949 | of the detector so that as much light reaches the PMTs as possible. |
---|
2950 | WLS fibers are also used to match the emission spectrum of the |
---|
2951 | detector with the input spectrum of the PMT. |
---|
2952 | </para> |
---|
2953 | |
---|
2954 | <para> |
---|
2955 | A WLS material is characterized by its photon absorption and |
---|
2956 | photon emission spectrum and by a possible time delay between the |
---|
2957 | absorption and re-emission of the photon. Wavelength Shifting may |
---|
2958 | be simulated by specifying these empirical parameters for each WLS |
---|
2959 | material in the simulation. It is sufficient to specify in the |
---|
2960 | user's <literal>DetectorConstruction</literal> class a relative spectral |
---|
2961 | distribution as a function of photon energy for the WLS material. |
---|
2962 | WLSABSLENGTH is the absorption length of the material as a function |
---|
2963 | of the photon's momentum. WLSCOMPONENT is the relative emission |
---|
2964 | spectrum of the material as a function of the photon's momentum, |
---|
2965 | and WLSTIMECONSTANT accounts for any time delay which may occur |
---|
2966 | between absorption and re-emission of the photon. An example is |
---|
2967 | shown in <xref linkend="programlist_PhysProc_9" />. |
---|
2968 | |
---|
2969 | <example id="programlist_PhysProc_9"> |
---|
2970 | <title> |
---|
2971 | Specification of WLS properties in <literal>DetectorConstruction</literal>. |
---|
2972 | </title> |
---|
2973 | |
---|
2974 | <programlisting> |
---|
2975 | const G4int nEntries = 9; |
---|
2976 | |
---|
2977 | G4double PhotonEnergy[nEntries] = { 6.6*eV, 6.7*eV, 6.8*eV, 6.9*eV, |
---|
2978 | 7.0*eV, 7.1*eV, 7.2*eV, 7.3*eV, 7.4*eV }; |
---|
2979 | |
---|
2980 | G4double RIndexFiber[nEntries] = |
---|
2981 | { 1.60, 1.60, 1.60, 1.60, 1.60, 1.60, 1.60, 1.60, 1.60 }; |
---|
2982 | G4double AbsFiber[nEntries] = |
---|
2983 | {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}; |
---|
2984 | G4double EmissionFiber[nEntries] = |
---|
2985 | {0.0, 0.0, 0.0, 0.1, 0.5, 1.0, 5.0, 10.0, 10.0 }; |
---|
2986 | |
---|
2987 | G4Material* WLSFiber; |
---|
2988 | G4MaterialPropertiesTable* MPTFiber = new G4MaterialPropertiesTable(); |
---|
2989 | |
---|
2990 | MPTFiber->AddProperty("RINDEX",PhotonEnergy,RIndexFiber,nEntries); |
---|
2991 | MPTFiber->AddProperty("WLSABSLENGTH",PhotonEnergy,AbsFiber,nEntries); |
---|
2992 | MPTFiber->AddProperty("WLSCOMPONENT",PhotonEnergy,EmissionFiber,nEntries); |
---|
2993 | MPTFiber->AddConstProperty("WLSTIMECONSTANT", 0.5*ns); |
---|
2994 | |
---|
2995 | WLSFiber->SetMaterialPropertiesTable(MPTFiber); |
---|
2996 | </programlisting> |
---|
2997 | </example> |
---|
2998 | </para> |
---|
2999 | |
---|
3000 | <para> |
---|
3001 | The process is defined in the PhysicsList in the usual way. The |
---|
3002 | process class name is G4OpWLS. It should be instantiated with |
---|
3003 | theWLSProcess = new G4OpWLS("OpWLS") and attached to the process |
---|
3004 | manager of the optical photon as a DiscreteProcess. The way the |
---|
3005 | WLSTIMECONSTANT is used depends on the time profile method chosen |
---|
3006 | by the user. If in the PhysicsList |
---|
3007 | theWLSProcess->UseTimeGenerator("exponential") option is set, |
---|
3008 | the time delay between absorption and re-emission of the photon is |
---|
3009 | sampled from an exponential distribution, with the decay term equal |
---|
3010 | to WLSTIMECONSTANT. If, on the other hand, |
---|
3011 | theWLSProcess->UseTimeGenerator("delta") is chosen, the time |
---|
3012 | delay is a delta function and equal to WLSTIMECONSTANT. The default |
---|
3013 | is "delta" in case the G4OpWLS::UseTimeGenerator(const G4String |
---|
3014 | name) method is not used. |
---|
3015 | </para> |
---|
3016 | |
---|
3017 | </sect3> |
---|
3018 | |
---|
3019 | |
---|
3020 | <!-- ******************* Section (Level#3) ****************** --> |
---|
3021 | <sect3 id="sect.PhysProc.Photo.Track"> |
---|
3022 | <title> |
---|
3023 | Tracking of Photons in <literal>processes/optical</literal> |
---|
3024 | </title> |
---|
3025 | |
---|
3026 | <!-- ******* Bridgehead ******* --> |
---|
3027 | <bridgehead renderas='sect4'> |
---|
3028 | Absorption |
---|
3029 | </bridgehead> |
---|
3030 | |
---|
3031 | <para> |
---|
3032 | The implementation of optical photon bulk absorption, |
---|
3033 | <literal>G4OpAbsorption</literal>, is trivial in that the process merely |
---|
3034 | kills the particle. The procedure requires the user to fill the |
---|
3035 | relevant <literal>G4MaterialPropertiesTable</literal> with empirical data for |
---|
3036 | the absorption length, using <literal>ABSLENGTH</literal> as the property key |
---|
3037 | in the public method <literal>AddProperty</literal>. The absorption length is |
---|
3038 | the average distance traveled by a photon before being absorpted by |
---|
3039 | the medium; i.e. it is the mean free path returned by the |
---|
3040 | <literal>GetMeanFreePath</literal> method. |
---|
3041 | </para> |
---|
3042 | |
---|
3043 | <!-- ******* Bridgehead ******* --> |
---|
3044 | <bridgehead renderas='sect4'> |
---|
3045 | Rayleigh Scattering |
---|
3046 | </bridgehead> |
---|
3047 | |
---|
3048 | <para> |
---|
3049 | The differential cross section in Rayleigh scattering, |
---|
3050 | σ/ω, is proportional |
---|
3051 | to cos<superscript>2</superscript>(&thetas;), |
---|
3052 | where &thetas; is the polar of the new polarization vector with |
---|
3053 | respect to the old polarization vector. The <literal>G4OpRayleigh</literal> |
---|
3054 | scattering process samples this angle accordingly and then |
---|
3055 | calculates the scattered photon's new direction by requiring that |
---|
3056 | it be perpendicular to the photon's new polarization in such a way |
---|
3057 | that the final direction, initial and final polarizations are all |
---|
3058 | in one plane. This process thus depends on the particle's |
---|
3059 | polarization (spin). The photon's polarization is a data member of |
---|
3060 | the <literal>G4DynamicParticle</literal> class. |
---|
3061 | </para> |
---|
3062 | |
---|
3063 | <para> |
---|
3064 | A photon which is not assigned a polarization at production, |
---|
3065 | either via the <literal>SetPolarization</literal> method of the |
---|
3066 | <literal>G4PrimaryParticle</literal> class, or indirectly with the |
---|
3067 | <literal>SetParticlePolarization</literal> method of the |
---|
3068 | <literal>G4ParticleGun</literal> class, may not be Rayleigh scattered. |
---|
3069 | Optical photons produced by the <literal>G4Cerenkov</literal> process have |
---|
3070 | inherently a polarization perpendicular to the cone's surface at |
---|
3071 | production. Scintillation photons have a random linear polarization |
---|
3072 | perpendicular to their direction. |
---|
3073 | </para> |
---|
3074 | |
---|
3075 | <para> |
---|
3076 | The process requires a <literal>G4MaterialPropertiesTable</literal> to be |
---|
3077 | filled by the user with Rayleigh scattering length data. The |
---|
3078 | Rayleigh scattering attenuation length is the average distance |
---|
3079 | traveled by a photon before it is Rayleigh scattered in the medium |
---|
3080 | and it is the distance returned by the <literal>GetMeanFreePath</literal> |
---|
3081 | method. The <literal>G4OpRayleigh</literal> class provides a |
---|
3082 | <literal>RayleighAttenuationLengthGenerator</literal> method which calculates |
---|
3083 | the attenuation coefficient of a medium following the |
---|
3084 | Einstein-Smoluchowski formula whose derivation requires the use of |
---|
3085 | statistical mechanics, includes temperature, and depends on the |
---|
3086 | isothermal compressibility of the medium. This generator is |
---|
3087 | convenient when the Rayleigh attenuation length is not known from |
---|
3088 | measurement but may be calculated from first principles using the |
---|
3089 | above material constants. For a medium named <emphasis>Water</emphasis> and no |
---|
3090 | Rayleigh scattering attenutation length specified by the user, the |
---|
3091 | program automatically calls the |
---|
3092 | <literal>RayleighAttenuationLengthGenerator</literal> |
---|
3093 | which calculates it for 10 degrees Celsius liquid water. |
---|
3094 | </para> |
---|
3095 | |
---|
3096 | <!-- ******* Bridgehead ******* --> |
---|
3097 | <bridgehead renderas='sect4'> |
---|
3098 | Boundary Process |
---|
3099 | </bridgehead> |
---|
3100 | |
---|
3101 | <para> |
---|
3102 | Reference: E. Hecht and A. Zajac, Optics |
---|
3103 | <citation> |
---|
3104 | <xref linkend="biblio.hecht1974" endterm="biblio.hecht1974.abbrev" /> |
---|
3105 | </citation> |
---|
3106 | </para> |
---|
3107 | |
---|
3108 | <para> |
---|
3109 | For the simple case of a perfectly smooth interface between two |
---|
3110 | dielectric materials, all the user needs to provide are the |
---|
3111 | refractive indices of the two materials stored in their respective |
---|
3112 | <literal>G4MaterialPropertiesTable</literal>. In all other cases, the optical |
---|
3113 | boundary process design relies on the concept of <emphasis>surfaces</emphasis>. |
---|
3114 | The information is split into two classes. One class in the |
---|
3115 | material category keeps information about the physical properties |
---|
3116 | of the surface itself, and a second class in the geometry category |
---|
3117 | holds pointers to the relevant physical and logical volumes |
---|
3118 | involved and has an association to the physical class. Surface |
---|
3119 | objects of the second type are stored in a related table and can be |
---|
3120 | retrieved by either specifying the two ordered pairs of physical |
---|
3121 | volumes touching at the surface, or by the logical volume entirely |
---|
3122 | surrounded by this surface. The former is called a <emphasis>border |
---|
3123 | surface</emphasis> while the latter is referred to as the <emphasis>skin |
---|
3124 | surface</emphasis>. This second type of surface is useful in situations |
---|
3125 | where a volume is coded with a reflector and is placed into many |
---|
3126 | different mother volumes. A limitation is that the skin surface can |
---|
3127 | only have one and the same optical property for all of the enclosed |
---|
3128 | volume's sides. The border surface is an ordered pair of physical |
---|
3129 | volumes, so in principle, the user can choose different optical |
---|
3130 | properties for photons arriving from the reverse side of the same |
---|
3131 | interface. For the optical boundary process to use a border |
---|
3132 | surface, the two volumes must have been positioned with |
---|
3133 | <literal>G4PVPlacement</literal>. The ordered combination can exist at many |
---|
3134 | places in the simulation. When the surface concept is not needed, |
---|
3135 | and a perfectly smooth surface exists beteen two dielectic |
---|
3136 | materials, the only relevant property is the index of refraction, a |
---|
3137 | quantity stored with the material, and no restriction exists on how |
---|
3138 | the volumes were positioned. |
---|
3139 | </para> |
---|
3140 | |
---|
3141 | <para> |
---|
3142 | The physical surface object also specifies which model the |
---|
3143 | boundary process should use to simulate interactions with that |
---|
3144 | surface. In addition, the physical surface can have a material |
---|
3145 | property table all its own. The usage of this table allows all |
---|
3146 | specular constants to be wavelength dependent. In case the surface |
---|
3147 | is painted or wrapped (but not a cladding), the table may include |
---|
3148 | the thin layer's index of refraction. This allows the simulation of |
---|
3149 | boundary effects at the intersection between the medium and the |
---|
3150 | surface layer, as well as the Lambertian reflection at the far side |
---|
3151 | of the thin layer. This occurs within the process itself and does |
---|
3152 | not invoke the <literal>G4Navigator</literal>. Combinations of surface finish |
---|
3153 | properties, such as <emphasis>polished</emphasis> or |
---|
3154 | <emphasis>ground</emphasis> and <emphasis>front |
---|
3155 | painted</emphasis> or <emphasis>back painted</emphasis>, enumerate the different |
---|
3156 | situations which can be simulated. |
---|
3157 | </para> |
---|
3158 | |
---|
3159 | <para> |
---|
3160 | When a photon arrives at a medium boundary its behavior depends |
---|
3161 | on the nature of the two materials that join at that boundary. |
---|
3162 | Medium boundaries may be formed between two dielectric materials or |
---|
3163 | a dielectric and a metal. In the case of two dielectric materials, |
---|
3164 | the photon can undergo total internal reflection, refraction or |
---|
3165 | reflection, depending on the photon's wavelength, angle of |
---|
3166 | incidence, and the refractive indices on both sides of the |
---|
3167 | boundary. Furthermore, reflection and transmission probabilites are |
---|
3168 | sensitive to the state of linear polarization. In the case of an |
---|
3169 | interface between a dielectric and a metal, the photon can be |
---|
3170 | absorbed by the metal or reflected back into the dielectric. If the |
---|
3171 | photon is absorbed it can be detected according to the |
---|
3172 | photoelectron efficiency of the metal. |
---|
3173 | </para> |
---|
3174 | |
---|
3175 | <para> |
---|
3176 | As expressed in Maxwell's equations, Fresnel reflection and |
---|
3177 | refraction are intertwined through their relative probabilities of |
---|
3178 | occurrence. Therefore neither of these processes, nor total |
---|
3179 | internal reflection, are viewed as individual processes deserving |
---|
3180 | separate class implementation. Nonetheless, an attempt was made to |
---|
3181 | adhere to the abstraction of having independent processes by |
---|
3182 | splitting the code into different methods where practicable. |
---|
3183 | </para> |
---|
3184 | |
---|
3185 | <para> |
---|
3186 | One implementation of the <literal>G4OpBoundaryProcess</literal> class |
---|
3187 | employs the |
---|
3188 | <ulink url="http://geant4.slac.stanford.edu/UsersWorkshop/G4Lectures/Peter/moisan.ps"> |
---|
3189 | UNIFIED model</ulink> |
---|
3190 | [A. Levin and C. Moisan, A More Physical Approach |
---|
3191 | to Model the Surface Treatment of Scintillation Counters and its |
---|
3192 | Implementation into DETECT, TRIUMF Preprint TRI-PP-96-64, Oct. |
---|
3193 | 1996] of the DETECT program [G.F. Knoll, T.F. Knoll and T.M. |
---|
3194 | Henderson, Light Collection Scintillation Detector Composites for |
---|
3195 | Neutron Detection, IEEE Trans. Nucl. Sci., 35 (1988) 872.]. It |
---|
3196 | applies to dielectric-dielectric interfaces and tries to provide a |
---|
3197 | realistic simulation, which deals with all aspects of surface |
---|
3198 | finish and reflector coating. The surface may be assumed as smooth |
---|
3199 | and covered with a metallized coating representing a specular |
---|
3200 | reflector with given reflection coefficient, or painted with a |
---|
3201 | diffuse reflecting material where Lambertian reflection occurs. The |
---|
3202 | surfaces may or may not be in optical contact with another |
---|
3203 | component and most importantly, one may consider a surface to be |
---|
3204 | made up of micro-facets with normal vectors that follow given |
---|
3205 | distributions around the nominal normal for the volume at the |
---|
3206 | impact point. For very rough surfaces, it is possible for the |
---|
3207 | photon to inversely aim at the same surface again after reflection |
---|
3208 | of refraction and so multiple interactions with the boundary are |
---|
3209 | possible within the process itself and without the need for |
---|
3210 | relocation by <literal>G4Navigator</literal>. |
---|
3211 | </para> |
---|
3212 | |
---|
3213 | <para> |
---|
3214 | The UNIFIED model provides for a range of different reflection |
---|
3215 | mechanisms. The specular lobe constant represents the reflection |
---|
3216 | probability about the normal of a micro facet. The specular spike |
---|
3217 | constant, in turn, illustrates the probability of reflection about |
---|
3218 | the average surface normal. The diffuse lobe constant is for the |
---|
3219 | probability of internal Lambertian reflection, and finally the |
---|
3220 | back-scatter spike constant is for the case of several reflections |
---|
3221 | within a deep groove with the ultimate result of exact |
---|
3222 | back-scattering. The four probabilities must add up to one, with |
---|
3223 | the diffuse lobe constant being implicit. The reader may consult |
---|
3224 | the reference for a thorough description of the model. |
---|
3225 | |
---|
3226 | <example id="programlist_PhysProc_10"> |
---|
3227 | <title> |
---|
3228 | Dielectric-dielectric surface properties |
---|
3229 | defined via the <emphasis>G4OpticalSurface</emphasis>. |
---|
3230 | </title> |
---|
3231 | |
---|
3232 | <programlisting> |
---|
3233 | G4VPhysicalVolume* volume1; |
---|
3234 | G4VPhysicalVolume* volume2; |
---|
3235 | |
---|
3236 | G4OpticalSurface* OpSurface = new G4OpticalSurface("name"); |
---|
3237 | |
---|
3238 | G4LogicalBorderSurface* Surface = new |
---|
3239 | G4LogicalBorderSurface("name",volume1,volume2,OpSurface); |
---|
3240 | |
---|
3241 | G4double sigma_alpha = 0.1; |
---|
3242 | |
---|
3243 | OpSurface -> SetType(dielectric_dielectric); |
---|
3244 | OpSurface -> SetModel(unified); |
---|
3245 | OpSurface -> SetFinish(groundbackpainted); |
---|
3246 | OpSurface -> SetSigmaAlpha(sigma_alpha); |
---|
3247 | |
---|
3248 | const G4int NUM = 2; |
---|
3249 | |
---|
3250 | G4double pp[NUM] = {2.038*eV, 4.144*eV}; |
---|
3251 | G4double specularlobe[NUM] = {0.3, 0.3}; |
---|
3252 | G4double specularspike[NUM] = {0.2, 0.2}; |
---|
3253 | G4double backscatter[NUM] = {0.1, 0.1}; |
---|
3254 | G4double rindex[NUM] = {1.35, 1.40}; |
---|
3255 | G4double reflectivity[NUM] = {0.3, 0.5}; |
---|
3256 | G4double efficiency[NUM] = {0.8, 0.1}; |
---|
3257 | |
---|
3258 | G4MaterialPropertiesTable* SMPT = new G4MaterialPropertiesTable(); |
---|
3259 | |
---|
3260 | SMPT -> AddProperty("RINDEX",pp,rindex,NUM); |
---|
3261 | SMPT -> AddProperty("SPECULARLOBECONSTANT",pp,specularlobe,NUM); |
---|
3262 | SMPT -> AddProperty("SPECULARSPIKECONSTANT",pp,specularspike,NUM); |
---|
3263 | SMPT -> AddProperty("BACKSCATTERCONSTANT",pp,backscatter,NUM); |
---|
3264 | SMPT -> AddProperty("REFLECTIVITY",pp,reflectivity,NUM); |
---|
3265 | SMPT -> AddProperty("EFFICIENCY",pp,efficiency,NUM); |
---|
3266 | |
---|
3267 | OpSurface -> SetMaterialPropertiesTable(SMPT); |
---|
3268 | </programlisting> |
---|
3269 | </example> |
---|
3270 | </para> |
---|
3271 | |
---|
3272 | <para> |
---|
3273 | The original |
---|
3274 | <ulink url="http://wwwasdoc.web.cern.ch/wwwasdoc/geant_html3/node231.html"> |
---|
3275 | GEANT3.21 implementation</ulink> of this process is also available via |
---|
3276 | the GLISUR methods flag. [GEANT Detector Description and Simulation |
---|
3277 | Tool, Application Software Group, Computing and Networks Division, |
---|
3278 | CERN, PHYS260-6 tp 260-7.]. |
---|
3279 | |
---|
3280 | <example id="programlist_PhysProc_11"> |
---|
3281 | <title> |
---|
3282 | Dielectric metal surface properties defined via the |
---|
3283 | <emphasis>G4OpticalSurface</emphasis>. |
---|
3284 | </title> |
---|
3285 | |
---|
3286 | <programlisting> |
---|
3287 | G4LogicalVolume* volume_log; |
---|
3288 | |
---|
3289 | G4OpticalSurface* OpSurface = new G4OpticalSurface("name"); |
---|
3290 | |
---|
3291 | G4LogicalSkinSurface* Surface = new |
---|
3292 | G4LogicalSkinSurface("name",volume_log,OpSurface); |
---|
3293 | |
---|
3294 | OpSurface -> SetType(dielectric_metal); |
---|
3295 | OpSurface -> SetFinish(ground); |
---|
3296 | OpSurface -> SetModel(glisur); |
---|
3297 | |
---|
3298 | G4double polish = 0.8; |
---|
3299 | |
---|
3300 | G4MaterialPropertiesTable *OpSurfaceProperty = new G4MaterialPropertiesTable(); |
---|
3301 | |
---|
3302 | OpSurfaceProperty -> AddProperty("REFLECTIVITY",pp,reflectivity,NUM); |
---|
3303 | OpSurfaceProperty -> AddProperty("EFFICIENCY",pp,efficiency,NUM); |
---|
3304 | |
---|
3305 | OpSurface -> SetMaterialPropertiesTable(OpSurfaceProperty); |
---|
3306 | </programlisting> |
---|
3307 | </example> |
---|
3308 | </para> |
---|
3309 | |
---|
3310 | <para> |
---|
3311 | The reflectivity off a metal surface can also be calculated by way of a complex |
---|
3312 | index of refraction. Instead of storing the REFLECTIVITY directly, the user |
---|
3313 | stores the real part (REALRINDEX) and the imaginary part (IMAGINARYRINDEX) as |
---|
3314 | a function of photon energy separately in the G4MaterialPropertyTable. Geant4 |
---|
3315 | then |
---|
3316 | <ulink url="./AllResources/TrackingAndPhysics/physicsProcessOptical.src/GetReflectivity.pdf"> |
---|
3317 | calculates the reflectivity |
---|
3318 | </ulink> |
---|
3319 | depending on the incident angle, photon energy, degree of TE and TM |
---|
3320 | polarization, and this complex refractive index. |
---|
3321 | </para> |
---|
3322 | |
---|
3323 | <para> |
---|
3324 | The program defaults to the GLISUR model and <emphasis>polished</emphasis> |
---|
3325 | surface finish when no specific model and surface finish is |
---|
3326 | specified by the user. In the case of a dielectric-metal interface, |
---|
3327 | or when the GLISUR model is specified, the only surface finish |
---|
3328 | options available are <emphasis>polished</emphasis> or <emphasis>ground</emphasis>. For |
---|
3329 | dielectric-metal surfaces, the <literal>G4OpBoundaryProcess</literal> also |
---|
3330 | defaults to unit reflectivity and zero detection efficiency. In |
---|
3331 | cases where the user specifies the UNIFIED model, but does not |
---|
3332 | otherwise specify the model reflection probability constants, the |
---|
3333 | default becomes Lambertian reflection. |
---|
3334 | </para> |
---|
3335 | |
---|
3336 | <para> |
---|
3337 | Martin Janecek and Bill Moses (Lawrence Berkeley National Laboratory) |
---|
3338 | built an instrument for measuring the angular reflectivity distribution |
---|
3339 | inside of BGO crystals with common surface treatments and reflectors |
---|
3340 | applied. These results have been incorporate into the Geant4 code. A |
---|
3341 | third class of reflection type besides dielectric_metal and |
---|
3342 | dielectric_dielectric is added: dielectric_LUT. The distributions have |
---|
3343 | been converted to 21 look-up-tables (LUT); so far for 1 scintillator |
---|
3344 | material (BGO) x 3 surface treatments x 7 reflector materials. The |
---|
3345 | modified code allows the user to specify the surface treatment |
---|
3346 | (rough-cut, chemically etched, or mechanically polished), the attached |
---|
3347 | reflector (Lumirror, Teflon, ESR film, Tyvek, or TiO2 paint), and the |
---|
3348 | bonding type (air-coupled or glued). The glue used is MeltMount, and the |
---|
3349 | ESR film used is VM2000. Each LUT consists of measured angular |
---|
3350 | distributions with 4º by 5º resolution in theta and phi, respectively, |
---|
3351 | for incidence angles from 0º to 90º degrees, in 1º-steps. The code might |
---|
3352 | in the future be updated by adding more LUTs, for instance, for other |
---|
3353 | scintillating materials (such as LSO or NaI). To use these LUT the user |
---|
3354 | has to download them from |
---|
3355 | <ulink url="http://geant4.web.cern.ch/geant4/support/download.shtml"> |
---|
3356 | Geant4 Software Download</ulink> and set an environment variable, |
---|
3357 | <literal>G4REALSURFACEDATA</literal>, to the directory of |
---|
3358 | <literal>geant4/data/RealSurface1.0</literal>. For details see: |
---|
3359 | |
---|
3360 | <ulink url="./AllResources/TrackingAndPhysics/physicsProcessOptical.src/Janecek-TNS-00249-2009R1.pdf"> |
---|
3361 | M. Janecek, W. Moses IEEE Transactions on Nuclear Science |
---|
3362 | </ulink>. |
---|
3363 | </para> |
---|
3364 | |
---|
3365 | <para> |
---|
3366 | The enumeration G4OpticalSurfaceFinish has been extended to include |
---|
3367 | (what follows should be a 2 column table): |
---|
3368 | |
---|
3369 | <informalexample> |
---|
3370 | <programlisting> |
---|
3371 | polishedlumirrorair, // mechanically polished surface, with lumirror |
---|
3372 | polishedlumirrorglue, // mechanically polished surface, with lumirror & meltmount |
---|
3373 | polishedair, // mechanically polished surface |
---|
3374 | polishedteflonair, // mechanically polished surface, with teflon |
---|
3375 | polishedtioair, // mechanically polished surface, with tio paint |
---|
3376 | polishedtyvekair, // mechanically polished surface, with tyvek |
---|
3377 | polishedvm2000air, // mechanically polished surface, with esr film |
---|
3378 | polishedvm2000glue, // mechanically polished surface, with esr film & meltmount |
---|
3379 | etchedlumirrorair, // chemically etched surface, with lumirror |
---|
3380 | etchedlumirrorglue, // chemically etched surface, with lumirror & meltmount |
---|
3381 | etchedair, // chemically etched surface |
---|
3382 | etchedteflonair, // chemically etched surface, with teflon |
---|
3383 | etchedtioair, // chemically etched surface, with tio paint |
---|
3384 | etchedtyvekair, // chemically etched surface, with tyvek |
---|
3385 | etchedvm2000air, // chemically etched surface, with esr film |
---|
3386 | etchedvm2000glue, // chemically etched surface, with esr film & meltmount |
---|
3387 | groundlumirrorair, // rough-cut surface, with lumirror |
---|
3388 | groundlumirrorglue, // rough-cut surface, with lumirror & meltmount |
---|
3389 | groundair, // rough-cut surface |
---|
3390 | groundteflonair, // rough-cut surface, with teflon |
---|
3391 | groundtioair, // rough-cut surface, with tio paint |
---|
3392 | groundtyvekair, // rough-cut surface, with tyvek |
---|
3393 | groundvm2000air, // rough-cut surface, with esr film |
---|
3394 | groundvm2000glue // rough-cut surface, with esr film & meltmount |
---|
3395 | </programlisting> |
---|
3396 | </informalexample> |
---|
3397 | </para> |
---|
3398 | |
---|
3399 | <para> |
---|
3400 | To use a look-up-table, all the user needs to specify for an |
---|
3401 | <literal>G4OpticalSurface</literal> is: |
---|
3402 | <literal>SetType(dielectric_LUT), SetModel(LUT)</literal> and for example, |
---|
3403 | <literal>SetFinish(polishedtyvekair)</literal>. |
---|
3404 | </para> |
---|
3405 | |
---|
3406 | </sect3> |
---|
3407 | </sect2> |
---|
3408 | |
---|
3409 | |
---|
3410 | <!-- ******************* Section (Level#2) ****************** --> |
---|
3411 | <sect2 id="sect.PhysProc.Param"> |
---|
3412 | <title> |
---|
3413 | Parameterization |
---|
3414 | </title> |
---|
3415 | |
---|
3416 | <para> |
---|
3417 | In this section we describe how to use the parameterization or |
---|
3418 | "fast simulation" facilities of GEANT4. Examples are provided in |
---|
3419 | the <emphasis role="bold">examples/novice/N05 directory</emphasis>. |
---|
3420 | </para> |
---|
3421 | |
---|
3422 | |
---|
3423 | <!-- ******************* Section (Level#3) ****************** --> |
---|
3424 | <sect3 id="sect.PhysProc.Param.Gene"> |
---|
3425 | <title> |
---|
3426 | Generalities: |
---|
3427 | </title> |
---|
3428 | |
---|
3429 | <para> |
---|
3430 | The Geant4 parameterization facilities allow you to shortcut the |
---|
3431 | detailed tracking in a given volume and for given particle types in |
---|
3432 | order for you to provide your own implementation of the physics and |
---|
3433 | of the detector response. |
---|
3434 | </para> |
---|
3435 | |
---|
3436 | <para> |
---|
3437 | Parameterisations are bound to a |
---|
3438 | <emphasis role="bold"><literal>G4Region</literal></emphasis> |
---|
3439 | object, which, in the case of fast simulation is also called an |
---|
3440 | <emphasis role="bold">envelope</emphasis>. Prior to release 8.0, |
---|
3441 | parameterisations were bound |
---|
3442 | to a <literal>G4LogicalVolume</literal>, the root of a volume hierarchy. |
---|
3443 | These root volumes are now attributes of the <literal>G4Region</literal>. |
---|
3444 | Envelopes often correspond to the volumes of sub-detectors: |
---|
3445 | electromagnetic calorimeters, tracking chambers, etc. With GEANT4 |
---|
3446 | it is also possible to define envelopes by overlaying a parallel or |
---|
3447 | "ghost" geometry as discussed in <xref linkend="sect.PhysProc.Param.Ghost" />. |
---|
3448 | </para> |
---|
3449 | |
---|
3450 | <para> |
---|
3451 | In GEANT4, parameterisations have three main features. You must |
---|
3452 | specify: |
---|
3453 | |
---|
3454 | <itemizedlist spacing="compact"> |
---|
3455 | <listitem><para> |
---|
3456 | the particle types for which your parameterisation is valid; |
---|
3457 | </para></listitem> |
---|
3458 | <listitem><para> |
---|
3459 | the dynamics conditions for which your parameterisation is |
---|
3460 | valid and must be triggered; |
---|
3461 | </para></listitem> |
---|
3462 | <listitem><para> |
---|
3463 | the parameterisation itself: where the primary will be killed |
---|
3464 | or moved, whether or not to create it or create secondaries, etc., |
---|
3465 | and where the detector response will be computed. |
---|
3466 | </para></listitem> |
---|
3467 | </itemizedlist> |
---|
3468 | </para> |
---|
3469 | |
---|
3470 | <para> |
---|
3471 | GEANT4 will message your parameterisation code for each step |
---|
3472 | starting in any root G4LogicalVolume (including daughters. |
---|
3473 | sub-daughters, etc. of this volume) of the <literal>G4Region</literal>. |
---|
3474 | It will proceed by first asking the available parameterisations for |
---|
3475 | the current particle type if one of them (and only one) wants to |
---|
3476 | issue a trigger. If so it will invoke its parameterisation. In this |
---|
3477 | case, the tracking |
---|
3478 | <emphasis role="bold"><emphasis>will not apply physics</emphasis></emphasis> |
---|
3479 | to the particle in the step. Instead, the UserSteppingAction will be |
---|
3480 | invoked. |
---|
3481 | </para> |
---|
3482 | |
---|
3483 | <para> |
---|
3484 | Parameterisations look like a "user stepping action" but are more |
---|
3485 | advanced because: |
---|
3486 | |
---|
3487 | <itemizedlist spacing="compact"> |
---|
3488 | <listitem><para> |
---|
3489 | parameterisation code is messaged only in the |
---|
3490 | <literal>G4Region</literal> to which it is bound; |
---|
3491 | </para></listitem> |
---|
3492 | <listitem><para> |
---|
3493 | parameterisation code is messaged anywhere in the |
---|
3494 | <literal>G4Region</literal>, that is, any volume in which the track is |
---|
3495 | located; |
---|
3496 | </para></listitem> |
---|
3497 | <listitem><para> |
---|
3498 | GEANT4 will provide information to your parameterisation code |
---|
3499 | about the current root volume of the <literal>G4Region</literal> |
---|
3500 | in which the track is travelling. |
---|
3501 | </para></listitem> |
---|
3502 | </itemizedlist> |
---|
3503 | </para> |
---|
3504 | |
---|
3505 | </sect3> |
---|
3506 | |
---|
3507 | |
---|
3508 | <!-- ******************* Section (Level#3) ****************** --> |
---|
3509 | <sect3 id="sect.PhysProc.Param.OvComp"> |
---|
3510 | <title> |
---|
3511 | Overview of Parameterisation Components |
---|
3512 | </title> |
---|
3513 | |
---|
3514 | <para> |
---|
3515 | The GEANT4 components which allow the implementation and control |
---|
3516 | of parameterisations are: |
---|
3517 | |
---|
3518 | <variablelist> |
---|
3519 | <varlistentry> |
---|
3520 | <term> |
---|
3521 | <literal><emphasis role="bold">G4VFastSimulationModel</emphasis></literal> |
---|
3522 | </term> |
---|
3523 | <listitem><para> |
---|
3524 | This is the abstract class for the implementation of parameterisations. |
---|
3525 | You must inherit from it to implement your concrete parameterisation model. |
---|
3526 | </para></listitem> |
---|
3527 | </varlistentry> |
---|
3528 | <varlistentry> |
---|
3529 | <term> |
---|
3530 | <literal><emphasis role="bold">G4FastSimulationManager</emphasis></literal> |
---|
3531 | </term> |
---|
3532 | <listitem><para> |
---|
3533 | The G4VFastSimulationModel objects are attached to the |
---|
3534 | <literal>G4Region</literal> through a G4FastSimulationManager. |
---|
3535 | This object will manage the list of models and will message them at |
---|
3536 | tracking time. |
---|
3537 | </para></listitem> |
---|
3538 | </varlistentry> |
---|
3539 | <varlistentry> |
---|
3540 | <term> |
---|
3541 | <literal><emphasis role="bold">G4Region/Envelope</emphasis></literal> |
---|
3542 | </term> |
---|
3543 | <listitem><para> |
---|
3544 | As mentioned before, an envelope in GEANT4 is a |
---|
3545 | <literal><emphasis role="bold">G4Region</emphasis></literal>. |
---|
3546 | The parameterisation is bound to the <literal>G4Region</literal> by |
---|
3547 | setting a <literal>G4FastSimulationManager</literal> pointer to it. |
---|
3548 | </para> |
---|
3549 | <para> |
---|
3550 | The figure below shows how the <literal>G4VFastSimulationModel</literal> |
---|
3551 | and <literal>G4FastSimulationManager</literal> objects are bound to the |
---|
3552 | <literal>G4Region</literal>. Then for all root G4LogicalVolume's held by |
---|
3553 | the G4Region, the fast simulation code is active. |
---|
3554 | |
---|
3555 | <mediaobject> |
---|
3556 | <imageobject role="fo"> |
---|
3557 | <imagedata fileref="./AllResources/TrackingAndPhysics/physicsProcessPARAM.src/ComponentsWithRegion.jpg" |
---|
3558 | format="JPG" contentwidth="7.0cm" align="center" /> |
---|
3559 | </imageobject> |
---|
3560 | <imageobject role="html"> |
---|
3561 | <imagedata fileref="./AllResources/TrackingAndPhysics/physicsProcessPARAM.src/ComponentsWithRegion.jpg" |
---|
3562 | format="JPG" align="center" /> |
---|
3563 | </imageobject> |
---|
3564 | <caption> |
---|
3565 | </caption> |
---|
3566 | </mediaobject> |
---|
3567 | |
---|
3568 | </para></listitem> |
---|
3569 | </varlistentry> |
---|
3570 | <varlistentry> |
---|
3571 | <term> |
---|
3572 | <literal><emphasis role="bold">G4FastSimulationManagerProcess</emphasis></literal> |
---|
3573 | </term> |
---|
3574 | <listitem><para> |
---|
3575 | This is a <literal>G4VProcess</literal>. It provides the interface |
---|
3576 | between the tracking and the parameterisation. It must be set in the |
---|
3577 | process list of the particles you want to parameterise. |
---|
3578 | </para></listitem> |
---|
3579 | </varlistentry> |
---|
3580 | <varlistentry> |
---|
3581 | <term> |
---|
3582 | <literal><emphasis role="bold">G4GlobalFastSimulationManager</emphasis></literal> |
---|
3583 | </term> |
---|
3584 | <listitem><para> |
---|
3585 | This a singleton class which provides the management of the |
---|
3586 | <literal>G4FastSimulationManager</literal> objects and some ghost |
---|
3587 | facilities. |
---|
3588 | </para></listitem> |
---|
3589 | </varlistentry> |
---|
3590 | </variablelist> |
---|
3591 | </para> |
---|
3592 | |
---|
3593 | </sect3> |
---|
3594 | |
---|
3595 | |
---|
3596 | <!-- ******************* Section (Level#3) ****************** --> |
---|
3597 | <sect3 id="sect.PhysProc.Param.FastSimModel"> |
---|
3598 | <title> |
---|
3599 | The <literal>G4VFastSimulationModel</literal> Abstract Class |
---|
3600 | </title> |
---|
3601 | |
---|
3602 | <!-- ******* Bridgehead ******* --> |
---|
3603 | <bridgehead renderas='sect4'> |
---|
3604 | Constructors: |
---|
3605 | </bridgehead> |
---|
3606 | |
---|
3607 | <para> |
---|
3608 | The <literal>G4VFastSimulationModel</literal> class has two constructors. |
---|
3609 | The second one allows you to get started quickly: |
---|
3610 | |
---|
3611 | <variablelist> |
---|
3612 | <varlistentry> |
---|
3613 | <term> |
---|
3614 | <emphasis role="bold"><literal>G4VFastSimulationModel( |
---|
3615 | const G4String& aName)</literal></emphasis>: |
---|
3616 | </term> |
---|
3617 | <listitem><para> |
---|
3618 | Here <literal>aName</literal> identifies the parameterisation model. |
---|
3619 | </para></listitem> |
---|
3620 | </varlistentry> |
---|
3621 | <varlistentry> |
---|
3622 | <term> |
---|
3623 | <emphasis role="bold"><literal>G4VFastSimulationModel(const G4String& |
---|
3624 | aName, G4Region*, G4bool IsUnique=false):</literal></emphasis> |
---|
3625 | </term> |
---|
3626 | <listitem><para> |
---|
3627 | In addition to the model name, this constructor accepts a G4Region pointer. |
---|
3628 | The needed G4FastSimulationManager object is constructed if necessary, |
---|
3629 | passing to it the G4Region pointer and the boolean value. If it |
---|
3630 | already exists, the model is simply added to this manager. Note |
---|
3631 | that the <emphasis>G4VFastSimulationModel object will not keep track of |
---|
3632 | the G4Region passed in the constructor</emphasis>. |
---|
3633 | The boolean argument is there for optimization purposes: if you |
---|
3634 | know that the G4Region has a unique root G4LogicalVolume, uniquely |
---|
3635 | placed, you can set the boolean value to "true". |
---|
3636 | </para></listitem> |
---|
3637 | </varlistentry> |
---|
3638 | </variablelist> |
---|
3639 | </para> |
---|
3640 | |
---|
3641 | <!-- ******* Bridgehead ******* --> |
---|
3642 | <bridgehead renderas='sect4'> |
---|
3643 | Virtual methods: |
---|
3644 | </bridgehead> |
---|
3645 | |
---|
3646 | <para> |
---|
3647 | The G4VFastSimulationModel has three pure virtual methods which |
---|
3648 | must be overriden in your concrete class: |
---|
3649 | |
---|
3650 | <variablelist> |
---|
3651 | <varlistentry> |
---|
3652 | <term> |
---|
3653 | <emphasis role="bold"><literal>G4VFastSimulationModel( |
---|
3654 | <emphasis>const G4String& aName</emphasis>):</literal></emphasis> |
---|
3655 | </term> |
---|
3656 | <listitem><para> |
---|
3657 | Here aName identifies the parameterisation model. |
---|
3658 | </para></listitem> |
---|
3659 | </varlistentry> |
---|
3660 | <varlistentry> |
---|
3661 | <term> |
---|
3662 | <emphasis role="bold"><literal>G4bool ModelTrigger( |
---|
3663 | <emphasis>const G4FastTrack&</emphasis>):</literal></emphasis> |
---|
3664 | </term> |
---|
3665 | <listitem><para> |
---|
3666 | You must return "true" when the dynamic conditions to trigger your |
---|
3667 | parameterisation are fulfilled. |
---|
3668 | G4FastTrack provides access to the current G4Track, gives simple |
---|
3669 | access to the current root G4LogicalVolume related features (its |
---|
3670 | G4VSolid, and G4AffineTransform references between the global and |
---|
3671 | the root G4LogicalVolume local coordinates systems) and simple |
---|
3672 | access to the position and momentum expressed in the root |
---|
3673 | G4LogicalVolume coordinate system. Using these quantities and the |
---|
3674 | G4VSolid methods, you can for example easily check how far you are |
---|
3675 | from the root G4LogicalVolume boundary. |
---|
3676 | </para></listitem> |
---|
3677 | </varlistentry> |
---|
3678 | <varlistentry> |
---|
3679 | <term> |
---|
3680 | <emphasis role="bold"><literal>G4bool IsApplicable( |
---|
3681 | <emphasis>const G4ParticleDefinition&</emphasis>):</literal></emphasis> |
---|
3682 | </term> |
---|
3683 | <listitem><para> |
---|
3684 | In your implementation, you must return "true" when your model is |
---|
3685 | applicable to the G4ParticleDefinition passed to this method. The |
---|
3686 | G4ParticleDefinition provides all intrinsic particle information |
---|
3687 | (mass, charge, spin, name ...). |
---|
3688 | </para> |
---|
3689 | <para> |
---|
3690 | If you want to implement a model which is valid only for certain |
---|
3691 | particle types, it is recommended for efficiency that you use the |
---|
3692 | static pointer of the corresponding particle classes. |
---|
3693 | </para> |
---|
3694 | <para> |
---|
3695 | As an example, in a model valid for <emphasis>gamma</emphasis>s only, |
---|
3696 | the IsApplicable() method should take the form: |
---|
3697 | |
---|
3698 | <informalexample> |
---|
3699 | <programlisting> |
---|
3700 | #include "G4Gamma.hh" |
---|
3701 | |
---|
3702 | G4bool MyGammaModel::IsApplicable(const G4ParticleDefinition& partDef) |
---|
3703 | { |
---|
3704 | return &partDef == G4Gamma::GammaDefinition(); |
---|
3705 | } |
---|
3706 | </programlisting> |
---|
3707 | </informalexample> |
---|
3708 | </para></listitem> |
---|
3709 | </varlistentry> |
---|
3710 | <varlistentry> |
---|
3711 | <term> |
---|
3712 | <emphasis role="bold"><literal>G4bool ModelTrigger( |
---|
3713 | <emphasis>const G4FastTrack&</emphasis>):</literal></emphasis> |
---|
3714 | </term> |
---|
3715 | <listitem><para> |
---|
3716 | You must return "true" when the dynamic conditions to trigger your |
---|
3717 | parameterisation are fulfilled. |
---|
3718 | The G4FastTrack provides access to the current G4Track, gives |
---|
3719 | simple access to envelope related features (G4LogicalVolume, |
---|
3720 | G4VSolid, and G4AffineTransform references between the global and |
---|
3721 | the envelope local coordinates systems) and simple access to the |
---|
3722 | position and momentum expressed in the envelope coordinate system. |
---|
3723 | Using these quantities and the G4VSolid methods, you can for |
---|
3724 | example easily check how far you are from the envelope boundary. |
---|
3725 | </para></listitem> |
---|
3726 | </varlistentry> |
---|
3727 | <varlistentry> |
---|
3728 | <term> |
---|
3729 | <emphasis role="bold"><literal>void DoIt( |
---|
3730 | <emphasis>const G4FastTrack&, G4FastStep&</emphasis>):</literal></emphasis> |
---|
3731 | </term> |
---|
3732 | <listitem><para> |
---|
3733 | The details of your parameterisation will be implemented in this method. |
---|
3734 | The G4FastTrack reference provides the input information, and the final |
---|
3735 | state of the particles after parameterisation must be returned |
---|
3736 | through the G4FastStep reference. Tracking for the final state |
---|
3737 | particles is requested after your parameterisation has been invoked. |
---|
3738 | </para></listitem> |
---|
3739 | </varlistentry> |
---|
3740 | </variablelist> |
---|
3741 | </para> |
---|
3742 | |
---|
3743 | </sect3> |
---|
3744 | |
---|
3745 | |
---|
3746 | <!-- ******************* Section (Level#3) ****************** --> |
---|
3747 | <sect3 id="sect.PhysProc.Param.FastSimMan"> |
---|
3748 | <title> |
---|
3749 | The <literal>G4FastSimulationManager</literal> Class: |
---|
3750 | </title> |
---|
3751 | |
---|
3752 | <para> |
---|
3753 | G4FastSimulationManager functionnalities regarding the use of ghost |
---|
3754 | volumes are explained in <xref linkend="sect.PhysProc.Param.Ghost" />. |
---|
3755 | </para> |
---|
3756 | |
---|
3757 | <!-- ******* Bridgehead ******* --> |
---|
3758 | <bridgehead renderas='sect4'> |
---|
3759 | Constructor: |
---|
3760 | </bridgehead> |
---|
3761 | |
---|
3762 | <para> |
---|
3763 | <variablelist> |
---|
3764 | <varlistentry> |
---|
3765 | <term> |
---|
3766 | <literal><emphasis role="bold">G4FastSimulationManager( |
---|
3767 | <emphasis>G4Region *anEnvelope, G4bool IsUnique=false</emphasis>): |
---|
3768 | </emphasis></literal> |
---|
3769 | </term> |
---|
3770 | <listitem><para> |
---|
3771 | This is the only constructor. You specify the G4Region by providing |
---|
3772 | its pointer. The G4FastSimulationManager object will bind itself |
---|
3773 | to this G4Region. If you know that this G4Region has a single root |
---|
3774 | G4LogicalVolume, placed only once, you can set the IsUnique boolean |
---|
3775 | to "true" to allow some optimization. |
---|
3776 | </para> |
---|
3777 | <para> |
---|
3778 | Note that if you choose to use the G4VFastSimulationModel(const |
---|
3779 | G4String&, G4Region*, G4bool) constructor for your model, the |
---|
3780 | G4FastSimulationManager will be constructed using the given |
---|
3781 | G4Region* and G4bool values of the model constructor. |
---|
3782 | </para></listitem> |
---|
3783 | </varlistentry> |
---|
3784 | </variablelist> |
---|
3785 | </para> |
---|
3786 | |
---|
3787 | <!-- ******* Bridgehead ******* --> |
---|
3788 | <bridgehead renderas='sect4'> |
---|
3789 | G4VFastSimulationModel object management: |
---|
3790 | </bridgehead> |
---|
3791 | |
---|
3792 | <para> |
---|
3793 | The following two methods provide the usual management |
---|
3794 | functions. |
---|
3795 | |
---|
3796 | <itemizedlist spacing="compact"> |
---|
3797 | <listitem><para> |
---|
3798 | <literal><emphasis role="bold">void AddFastSimulationModel( |
---|
3799 | G4VFastSimulationModel*)</emphasis></literal> |
---|
3800 | </para></listitem> |
---|
3801 | <listitem><para> |
---|
3802 | <literal><emphasis role="bold">RemoveFastSimulationModel( |
---|
3803 | G4VFastSimulationModel*)</emphasis></literal> |
---|
3804 | </para></listitem> |
---|
3805 | </itemizedlist> |
---|
3806 | </para> |
---|
3807 | |
---|
3808 | <!-- ******* Bridgehead ******* --> |
---|
3809 | <bridgehead renderas='sect4'> |
---|
3810 | Interface with the G4FastSimulationManagerProcess: |
---|
3811 | </bridgehead> |
---|
3812 | |
---|
3813 | <para> |
---|
3814 | This is described in the User's Guide for Toolkit Developers |
---|
3815 | ( |
---|
3816 | <!-- !!! xref linkend=""/ or ulink url="" --> |
---|
3817 | section 3.9.6 |
---|
3818 | <!-- !! /ulink (remove this tag for xref) --> |
---|
3819 | ) |
---|
3820 | </para> |
---|
3821 | |
---|
3822 | </sect3> |
---|
3823 | |
---|
3824 | <!-- ******************* Section (Level#3) ****************** --> |
---|
3825 | <sect3 id="sect.PhysProc.Param.FastSimManProc"> |
---|
3826 | <title> |
---|
3827 | The <literal>G4FastSimulationManagerProcess</literal> Class |
---|
3828 | </title> |
---|
3829 | |
---|
3830 | <para> |
---|
3831 | This G4VProcess serves as an interface between the tracking and the |
---|
3832 | parameterisation. At tracking time, it collaborates with the |
---|
3833 | G4FastSimulationManager of the current volume, if any, to allow the |
---|
3834 | models to trigger. If no manager exists or if no model issues a |
---|
3835 | trigger, the tracking goes on normally. |
---|
3836 | </para> |
---|
3837 | |
---|
3838 | <para> |
---|
3839 | <emphasis>In the present implementation, you must set this process in |
---|
3840 | the G4ProcessManager of the particles you parameterise to enable |
---|
3841 | your parameterisation.</emphasis> |
---|
3842 | </para> |
---|
3843 | |
---|
3844 | <para> |
---|
3845 | The processes ordering is: |
---|
3846 | |
---|
3847 | <informalexample> |
---|
3848 | <programlisting> |
---|
3849 | [n-3] ... |
---|
3850 | [n-2] Multiple Scattering |
---|
3851 | [n-1] G4FastSimulationManagerProcess |
---|
3852 | [ n ] G4Transportation |
---|
3853 | </programlisting> |
---|
3854 | </informalexample> |
---|
3855 | </para> |
---|
3856 | |
---|
3857 | <para> |
---|
3858 | This ordering is important if you use ghost geometries, since the |
---|
3859 | G4FastSimulationManagerProcess will provide navigation in the ghost |
---|
3860 | world to limit the step on ghost boundaries. |
---|
3861 | </para> |
---|
3862 | |
---|
3863 | <para> |
---|
3864 | The G4FastSimulationManager must be added to the process list of a |
---|
3865 | particle as a continuous and discrete process if you use ghost |
---|
3866 | geometries for this particle. You can add it as a discrete process |
---|
3867 | if you don't use ghosts. |
---|
3868 | </para> |
---|
3869 | |
---|
3870 | <para> |
---|
3871 | The following code registers the G4FastSimulationManagerProcess |
---|
3872 | with all the particles as a discrete and continuous process: |
---|
3873 | |
---|
3874 | <informalexample> |
---|
3875 | <programlisting> |
---|
3876 | void MyPhysicsList::addParameterisation() |
---|
3877 | { |
---|
3878 | G4FastSimulationManagerProcess* |
---|
3879 | theFastSimulationManagerProcess = new G4FastSimulationManagerProcess(); |
---|
3880 | theParticleIterator->reset(); |
---|
3881 | while( (*theParticleIterator)() ) |
---|
3882 | { |
---|
3883 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
3884 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
3885 | pmanager->AddProcess(theFastSimulationManagerProcess, -1, 0, 0); |
---|
3886 | } |
---|
3887 | } |
---|
3888 | </programlisting> |
---|
3889 | </informalexample> |
---|
3890 | </para> |
---|
3891 | |
---|
3892 | </sect3> |
---|
3893 | |
---|
3894 | <!-- ******************* Section (Level#3) ****************** --> |
---|
3895 | <sect3 id="sect.PhysProc.Param.FastSimManSing"> |
---|
3896 | <title> |
---|
3897 | The <literal>G4GlobalFastSimulationManager</literal> Singleton Class |
---|
3898 | </title> |
---|
3899 | |
---|
3900 | <para> |
---|
3901 | This class is a singleton which can be accessed as follows: |
---|
3902 | |
---|
3903 | <informalexample> |
---|
3904 | <programlisting> |
---|
3905 | #include "G4GlobalFastSimulationManager.hh" |
---|
3906 | ... |
---|
3907 | ... |
---|
3908 | G4GlobalFastSimulationManager* globalFSM; |
---|
3909 | globalFSM = G4GlobalFastSimulationManager::getGlobalFastSimulationManager(); |
---|
3910 | ... |
---|
3911 | ... |
---|
3912 | </programlisting> |
---|
3913 | </informalexample> |
---|
3914 | </para> |
---|
3915 | |
---|
3916 | <para> |
---|
3917 | Presently, you will mainly need to use the |
---|
3918 | GlobalFastSimulationManager if you use ghost geometries. |
---|
3919 | </para> |
---|
3920 | |
---|
3921 | </sect3> |
---|
3922 | |
---|
3923 | <!-- ******************* Section (Level#3) ****************** --> |
---|
3924 | <sect3 id="sect.PhysProc.Param.Ghost"> |
---|
3925 | <title> |
---|
3926 | Parameterisation Using Ghost Geometries |
---|
3927 | </title> |
---|
3928 | |
---|
3929 | <para> |
---|
3930 | In some cases, volumes of the tracking geometry do not allow |
---|
3931 | envelopes to be defined. This may be the case with a geometry |
---|
3932 | coming from a CAD system. Since such a geometry is flat, a parallel |
---|
3933 | geometry must be used to define the envelopes. |
---|
3934 | </para> |
---|
3935 | |
---|
3936 | <para> |
---|
3937 | Another interesting case involves defining an envelope which groups |
---|
3938 | the electromagnetic and hadronic calorimeters of a detector into |
---|
3939 | one volume. This may be useful when parameterizing the interaction |
---|
3940 | of charged pions. You will very likely not want electrons to see |
---|
3941 | this envelope, which means that ghost geometries have to be |
---|
3942 | organized by particle flavours. |
---|
3943 | </para> |
---|
3944 | |
---|
3945 | <para> |
---|
3946 | Using ghost geometries implies some more overhead in the |
---|
3947 | parameterisation mechanism for the particles sensitive to ghosts, |
---|
3948 | since navigation is provided in the ghost geometry by the |
---|
3949 | G4FastSimulationManagerProcess. Usually, however, only a few |
---|
3950 | volumes will be placed in this ghost world, so that the geometry |
---|
3951 | computations will remain rather cheap. |
---|
3952 | </para> |
---|
3953 | |
---|
3954 | <para> |
---|
3955 | In the existing implementation (temporary implementation with |
---|
3956 | G4Region but before parallel geometry implementation), you may only |
---|
3957 | consider ghost G4Regions with just one root G4LogicalVolume. The |
---|
3958 | G4GlobalFastSimulationManager provides the construction of the |
---|
3959 | ghost geometry by making first an empty "clone" of the world for |
---|
3960 | tracking provided by the construct() method of your |
---|
3961 | G4VUserDetectorConstruction concrete class. You provide the |
---|
3962 | placement of the G4Region root G4LogicalVolume relative to the |
---|
3963 | ghost world coordinates in the G4FastSimulationManager objects. A |
---|
3964 | ghost G4Region is recognized by the fact that its associated |
---|
3965 | G4FastSimulationManager retains a non-empty list of placements. |
---|
3966 | </para> |
---|
3967 | |
---|
3968 | <para> |
---|
3969 | The G4GlobalFastSimulationManager will then use both those |
---|
3970 | placements and the IsApplicable() methods of the models attached to |
---|
3971 | the G4FastSimulationManager objects to build the flavour-dependant |
---|
3972 | ghost geometries. |
---|
3973 | </para> |
---|
3974 | |
---|
3975 | <para> |
---|
3976 | Then at the beginning of the tracking of a particle, the |
---|
3977 | appropriate ghost world, if any, will be selected. |
---|
3978 | </para> |
---|
3979 | |
---|
3980 | <para> |
---|
3981 | The steps required to build one ghost G4Region are: |
---|
3982 | |
---|
3983 | <orderedlist spacing="compact"> |
---|
3984 | <listitem><para> |
---|
3985 | built the ghost G4Region : myGhostRegion; |
---|
3986 | </para></listitem> |
---|
3987 | <listitem><para> |
---|
3988 | build the root G4LogicalVolume: myGhostLogical, set it to |
---|
3989 | myGhostRegion; |
---|
3990 | </para></listitem> |
---|
3991 | <listitem><para> |
---|
3992 | build a G4FastSimulationManager object, myGhostFSManager, |
---|
3993 | giving myGhostRegion as argument of the constructor; |
---|
3994 | </para></listitem> |
---|
3995 | <listitem><para> |
---|
3996 | <para> |
---|
3997 | give to the G4FastSimulationManager the placement of the |
---|
3998 | myGhostLogical, by invoking for the G4FastSimulationManager method: |
---|
3999 | <informalexample> |
---|
4000 | <programlisting> |
---|
4001 | AddGhostPlacement(G4RotationMatrix*, const G4ThreeVector&); |
---|
4002 | </programlisting> |
---|
4003 | </informalexample> |
---|
4004 | or: |
---|
4005 | <informalexample> |
---|
4006 | <programlisting> |
---|
4007 | AddGhostPlacement(G4Transform3D*); |
---|
4008 | </programlisting> |
---|
4009 | </informalexample> |
---|
4010 | |
---|
4011 | where the rotation matrix and translation vector of the 3-D |
---|
4012 | transformation describe the placement relative to the ghost world |
---|
4013 | coordinates. |
---|
4014 | </para> |
---|
4015 | </para></listitem> |
---|
4016 | <listitem><para> |
---|
4017 | build your G4VFastSimulationModel objects and add them to the |
---|
4018 | myGhostFSManager. |
---|
4019 | <emphasis>The IsApplicable() methods of your models will be used by the |
---|
4020 | G4GlobalFastSimulationManager to build the ghost geometries |
---|
4021 | corresponding to a given particle type.</emphasis> |
---|
4022 | </para></listitem> |
---|
4023 | <listitem><para> |
---|
4024 | <para> |
---|
4025 | Invoke the G4GlobalFastSimulationManager method: |
---|
4026 | |
---|
4027 | <informalexample> |
---|
4028 | <programlisting> |
---|
4029 | G4GlobalFastSimulationManager::getGlobalFastSimulationManager()-> |
---|
4030 | |
---|
4031 | CloseFastSimulation(); |
---|
4032 | </programlisting> |
---|
4033 | </informalexample> |
---|
4034 | </para> |
---|
4035 | </para></listitem> |
---|
4036 | </orderedlist> |
---|
4037 | </para> |
---|
4038 | |
---|
4039 | <para> |
---|
4040 | This last call will cause the G4GlobalFastSimulationManager to |
---|
4041 | build the flavour-dependent ghost geometries. This call must be |
---|
4042 | done before the RunManager closes the geometry. (It is foreseen |
---|
4043 | that the run manager in the future will invoke the |
---|
4044 | CloseFastSimulation() to synchronize properly with the closing of |
---|
4045 | the geometry). |
---|
4046 | </para> |
---|
4047 | |
---|
4048 | <para> |
---|
4049 | Visualization facilities are provided for ghosts geometries. After |
---|
4050 | the CloseFastSimulation() invocation, it is possible to ask for the |
---|
4051 | drawing of ghosts in an interactive session. The basic commands |
---|
4052 | are: |
---|
4053 | |
---|
4054 | <itemizedlist spacing="compact"> |
---|
4055 | <listitem><para> |
---|
4056 | <para> |
---|
4057 | /vis/draw/Ghosts particle_name |
---|
4058 | </para> |
---|
4059 | <para> |
---|
4060 | which makes the drawing of the ghost geometry associated with the |
---|
4061 | particle specified by name in the command line. |
---|
4062 | </para> |
---|
4063 | </para></listitem> |
---|
4064 | <listitem><para> |
---|
4065 | /vis/draw/Ghosts |
---|
4066 | <para> |
---|
4067 | which draws all the ghost geometries. |
---|
4068 | </para> |
---|
4069 | </para></listitem> |
---|
4070 | </itemizedlist> |
---|
4071 | </para> |
---|
4072 | |
---|
4073 | </sect3> |
---|
4074 | |
---|
4075 | <!-- ******************* Section (Level#3) ****************** --> |
---|
4076 | <sect3 id="sect.PhysProc.Param.GFlash"> |
---|
4077 | <title> |
---|
4078 | Gflash Parameterization |
---|
4079 | </title> |
---|
4080 | |
---|
4081 | <para> |
---|
4082 | This section describes how to use the Gflash library. Gflash is a |
---|
4083 | concrete parameterization which is based on the equations and |
---|
4084 | parameters of the original Gflash package from H1(hep-ex/0001020, |
---|
4085 | Grindhammer & Peters, see physics manual) and uses the "fast |
---|
4086 | simulation" facilities of GEANT4 described above. Briefly, whenever |
---|
4087 | a e-/e+ particle enters the calorimeter, it is parameterized if it |
---|
4088 | has a minimum energy and the shower is expected to be contained in |
---|
4089 | the calorimeter (or " parameterization envelope"). If this is |
---|
4090 | fulfilled the particle is killed, as well as all secondaries, and |
---|
4091 | the energy is deposited according to the Gflash equations. An |
---|
4092 | example, provided in |
---|
4093 | <emphasis role="bold">examples/extended/parametrisation/gflash/</emphasis>, |
---|
4094 | shows how to interface Gflash to your application. The simulation time is |
---|
4095 | measured, so the user can immediately see the speed increase |
---|
4096 | resulting from the use of Gflash. |
---|
4097 | </para> |
---|
4098 | |
---|
4099 | </sect3> |
---|
4100 | |
---|
4101 | <!-- ******************* Section (Level#3) ****************** --> |
---|
4102 | <sect3 id="sect.PhysProc.Param.UsingGFlash"> |
---|
4103 | <title> |
---|
4104 | Using the Gflash Parameterisation |
---|
4105 | </title> |
---|
4106 | |
---|
4107 | <para> |
---|
4108 | To use Gflash "out of the box" the following steps are necessary: |
---|
4109 | |
---|
4110 | <itemizedlist spacing="compact"> |
---|
4111 | <listitem><para> |
---|
4112 | The user must add the fast simulation process to his process |
---|
4113 | manager: |
---|
4114 | |
---|
4115 | <informalexample> |
---|
4116 | <programlisting> |
---|
4117 | void MyPhysicsList::addParameterisation() |
---|
4118 | { |
---|
4119 | G4FastSimulationManagerProcess* |
---|
4120 | theFastSimulationManagerProcess = new G4FastSimulationManagerProcess(); |
---|
4121 | theParticleIterator->reset(); |
---|
4122 | while( (*theParticleIterator)() ) |
---|
4123 | { |
---|
4124 | G4ParticleDefinition* particle = theParticleIterator->value(); |
---|
4125 | G4ProcessManager* pmanager = particle->GetProcessManager(); |
---|
4126 | pmanager->AddProcess(theFastSimulationManagerProcess, -1, 0, 0); |
---|
4127 | } |
---|
4128 | } |
---|
4129 | </programlisting> |
---|
4130 | </informalexample> |
---|
4131 | </para></listitem> |
---|
4132 | <listitem><para> |
---|
4133 | <para> |
---|
4134 | The envelope in which the parameterization should be performed |
---|
4135 | must be specified (below: G4Region m_calo_region) and the |
---|
4136 | GFlashShowerModel must be assigned to this region. Furthermore, the |
---|
4137 | classes GFlashParticleBounds (which provides thresholds for the |
---|
4138 | parameterization like minimal energy etc.), GflashHitMaker(a helper |
---|
4139 | class to generate hits in the sensitive detector) and |
---|
4140 | GFlashHomoShowerParamterisation (which does the computations) must |
---|
4141 | be constructed (by the user at the moment) and assigned to the |
---|
4142 | GFlashShowerModel. Please note that at the moment only homogeneous |
---|
4143 | calorimeters are supported. |
---|
4144 | </para> |
---|
4145 | <para> |
---|
4146 | <informalexample> |
---|
4147 | <programlisting> |
---|
4148 | m_theFastShowerModel = new GFlashShowerModel("fastShowerModel",m_calo_region); |
---|
4149 | m_theParametrisation = new GFlashHomoShowerParamterisation(matManager->getMaterial(mat)); |
---|
4150 | m_theParticleBounds = new GFlashParticleBounds(); |
---|
4151 | m_theHMaker = new GFlashHitMaker(); |
---|
4152 | m_theFastShowerModel->SetParametrisation(*m_theParametrisation); |
---|
4153 | m_theFastShowerModel->SetParticleBounds(*m_theParticleBounds) ; |
---|
4154 | m_theFastShowerModel->SetHitMaker(*m_theHMaker); |
---|
4155 | </programlisting> |
---|
4156 | </informalexample> |
---|
4157 | </para> |
---|
4158 | <para> |
---|
4159 | The user must also set the material of the calorimeter, since the |
---|
4160 | computation depends on the material. |
---|
4161 | </para> |
---|
4162 | </para></listitem> |
---|
4163 | <listitem><para> |
---|
4164 | <para> |
---|
4165 | It is mandatory to use G4VGFlashSensitiveDetector as |
---|
4166 | (additional) base class for the sensitive detector. |
---|
4167 | </para> |
---|
4168 | <para> |
---|
4169 | <informalexample> |
---|
4170 | <programlisting> |
---|
4171 | class ExGflashSensitiveDetector: public G4VSensitiveDetector ,public G4VGFlashSensitiveDetector |
---|
4172 | </programlisting> |
---|
4173 | </informalexample> |
---|
4174 | </para> |
---|
4175 | <para> |
---|
4176 | Here it is necessary to implement a separate interface, where the |
---|
4177 | GFlash spots are processed. |
---|
4178 | </para> |
---|
4179 | <para> |
---|
4180 | <informalexample> |
---|
4181 | <programlisting> |
---|
4182 | (ProcessHits(G4GFlashSpot*aSpot ,G4TouchableHistory* ROhist)) |
---|
4183 | </programlisting> |
---|
4184 | </informalexample> |
---|
4185 | </para> |
---|
4186 | <para> |
---|
4187 | A separate interface is used, because the Gflash spots naturally |
---|
4188 | contain less information than the full simulation. |
---|
4189 | </para> |
---|
4190 | </para></listitem> |
---|
4191 | </itemizedlist> |
---|
4192 | </para> |
---|
4193 | |
---|
4194 | <para> |
---|
4195 | Since the parameters in the Gflash package are taken from fits to |
---|
4196 | full simulations with Geant3, some retuning might be necessary for |
---|
4197 | good agreement with Geant4 showers. For experiment-specific |
---|
4198 | geometries some retuning might be necessary anyway. The tuning is |
---|
4199 | quite complicated since there are many parameters (some correlated) |
---|
4200 | and cannot be described here (see again hep-ex/0001020). For brave |
---|
4201 | users the Gflash framework already forsees the possibility of |
---|
4202 | passing a class with the (users) |
---|
4203 | parameters,<emphasis role="bold">GVFlashHomoShowerTuning</emphasis>, |
---|
4204 | to the GFlashHomoShowerParamterisation constructor. |
---|
4205 | The default parameters are the original Gflash parameters: |
---|
4206 | |
---|
4207 | <informalexample> |
---|
4208 | <programlisting> |
---|
4209 | GFlashHomoShowerParameterisation(G4Material * aMat, GVFlashHomoShowerTuning * aPar = 0); |
---|
4210 | </programlisting> |
---|
4211 | </informalexample> |
---|
4212 | </para> |
---|
4213 | |
---|
4214 | <para> |
---|
4215 | Now there is also a preliminary implemenation of a parameterization |
---|
4216 | for sampling calorimeters. |
---|
4217 | </para> |
---|
4218 | |
---|
4219 | <para> |
---|
4220 | The user must specify the active and passive material, as well as |
---|
4221 | the thickness of the active and passive layer. |
---|
4222 | </para> |
---|
4223 | |
---|
4224 | <para> |
---|
4225 | The sampling structure of the calorimeter is taken into account by |
---|
4226 | using an "effective medium" to compute the shower shape. |
---|
4227 | </para> |
---|
4228 | |
---|
4229 | <para> |
---|
4230 | All material properties needed are calculated automatically. If |
---|
4231 | tuning is required, the user can pass his own parameter set in |
---|
4232 | the class |
---|
4233 | <emphasis role="bold">GFlashSamplingShowerTuning</emphasis>. |
---|
4234 | Here the user can also set his calorimeter resolution. |
---|
4235 | </para> |
---|
4236 | |
---|
4237 | <para> |
---|
4238 | All in all the constructor looks the following: |
---|
4239 | |
---|
4240 | <informalexample> |
---|
4241 | <programlisting> |
---|
4242 | GFlashSamplingShowerParamterisation(G4Material * Mat1, G4Material * Mat2,G4double d1,G4double d2, |
---|
4243 | GVFlashSamplingShowerTuning * aPar = 0); |
---|
4244 | </programlisting> |
---|
4245 | </informalexample> |
---|
4246 | </para> |
---|
4247 | |
---|
4248 | <para> |
---|
4249 | An implementation of some tools that should help the user to tune |
---|
4250 | the parameterization is forseen. |
---|
4251 | </para> |
---|
4252 | |
---|
4253 | </sect3> |
---|
4254 | </sect2> |
---|
4255 | |
---|
4256 | |
---|
4257 | <!-- ******************* Section (Level#2) ****************** --> |
---|
4258 | <sect2 id="sect.PhysProc.Trans"> |
---|
4259 | <title> |
---|
4260 | Transportation Process |
---|
4261 | </title> |
---|
4262 | |
---|
4263 | <para> |
---|
4264 | To be delivered by J. Apostolakis (<email>John.Apostolakis@cern.ch</email>). |
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4265 | </para> |
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4266 | |
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4267 | |
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4268 | </sect2> |
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4269 | </sect1> |
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