1 | $Id: README,v 1.28 2010/06/06 04:25:24 perl Exp $ |
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2 | ------------------------------------------------------------------- |
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3 | |
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4 | ========================================================= |
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5 | Geant4 - an Object-Oriented Toolkit for Simulation in HEP |
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6 | ========================================================= |
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7 | |
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8 | TestEm1 |
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9 | ------- |
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10 | How to count processes. |
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11 | How to activate/inactivate processes. |
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12 | How to survey the tracking, in perticular the range of charged particles. |
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13 | How to define a maximum step size. |
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14 | |
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15 | 1 - GEOMETRY DEFINITION |
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16 | |
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17 | It is a simple box which represente an 'semi infinite' homogeneous medium. |
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18 | |
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19 | Two parameters define the geometry : |
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20 | - the material of the box, |
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21 | - the full size of the box. |
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22 | |
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23 | In addition a transverse uniform magnetic field can be applied. |
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24 | |
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25 | The default geometry is constructed in DetectorConstruction class, but all of |
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26 | the above parameters can be changed interactively via the commands defined in |
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27 | the DetectorMessenger class. |
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28 | |
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29 | 2 - PHYSICS LIST |
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30 | |
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31 | Physics lists can be local (eg. in this example) or from G4 kernel |
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32 | physics_lists subdirectory. |
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33 | |
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34 | Local physics list: |
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35 | - "local" standard EM physics with current 'best' options setting. |
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36 | these options are explicited in PhysListEmStandard |
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37 | |
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38 | From geant4/source/physics_lists/builders: |
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39 | - "emstandard_opt0" recommended standard EM physics for LHC |
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40 | - "emstandard_opt1" best CPU performance standard physics for LHC |
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41 | - "emstandard_opt2" |
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42 | - "emstandard_opt3" best current advanced EM options. |
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43 | analog to "local" above |
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44 | |
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45 | Physics lists and options can be (re)set with UI commands |
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46 | |
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47 | Please, notice that options set through G4EmProcessOPtions are global, eg |
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48 | for all particle types. In G4 builders (geant4/source/physics_lists/builders) |
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49 | it is shown how to set options per particle type. |
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50 | |
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51 | Few commands have been added to PhysicsList, in order to set the production |
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52 | threshold for secondaries for gamma and e-/e+. |
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53 | |
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54 | 3 - AN EVENT : THE PRIMARY GENERATOR |
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55 | |
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56 | The primary kinematic consists of a single particle starting at the left face |
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57 | of the box. The type of the particle and its energy are set in the |
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58 | PrimaryGeneratorAction class, and can be changed via the G4 build-in commands |
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59 | of ParticleGun class (see the macros provided with this example). |
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60 | |
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61 | In addition one can choose randomly the impact point of the incident particle. |
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62 | The corresponding interactive command is built in PrimaryGeneratorMessenger. |
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63 | |
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64 | 4 - VISUALIZATION |
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65 | |
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66 | The Visualization Manager is set in the main(). |
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67 | The initialisation of the drawing is done via the commands /vis/... in the |
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68 | macro vis.mac. To get visualisation: |
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69 | > /control/execute vis.mac |
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70 | |
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71 | The detector has a default view which is a longitudinal view of the box. |
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72 | |
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73 | The tracks are drawn at the end of event, and erased at the end of run. |
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74 | |
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75 | 5 - PHYSICS SURVEY |
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76 | |
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77 | The particle's type and the physic processes which will be available in this |
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78 | example are set in PhysicsList class. |
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79 | |
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80 | A set of macros defining various run conditions are provided. The processes |
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81 | are actived/inactived together with differents cuts, in order to survey the |
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82 | processes one by one. |
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83 | |
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84 | The number of produced secondaries are counted, the number of steps, and the |
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85 | number of process calls responsible of the step. |
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86 | |
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87 | 6 - HOW TO START ? |
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88 | |
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89 | - compile and link to generate an executable |
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90 | % cd geant4/examples/extended/electromagnetic/TestEm1 |
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91 | % gmake |
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92 | |
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93 | - execute TestEm1 in 'batch' mode from macro files |
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94 | % TestEm1 run10.mac |
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95 | |
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96 | - execute TestEm1 in 'interactive mode' with visualization |
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97 | % TestEm1 |
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98 | .... |
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99 | Idle> type your commands |
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100 | .... |
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101 | Idle> exit |
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102 | |
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103 | 7 - TRACKING : StepMax |
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104 | |
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105 | In order to control the accuracy of the deposition, the user can limit |
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106 | 'by hand' the maximum step size of charged particles. |
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107 | As an example, this limitation is implemented as a 'full' process : |
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108 | see StepMax class and its Messenger. The 'StepMax process' is registered |
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109 | in the Physics List. |
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110 | |
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111 | 8 - HISTOGRAMS |
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112 | |
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113 | Testem1 produces several histo which are saved as testem1.root by default. |
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114 | Content of these histo: |
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115 | 1 : track length of primary particle |
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116 | 2 : number of steps primary particle |
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117 | 3 : step size of primary particle |
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118 | |
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119 | The histograms are managed by the HistoManager class and its Messenger. |
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120 | The histos can be individually activated with the command : |
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121 | /testem/histo/setHisto id nbBins valMin valMax unit |
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122 | where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..) |
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123 | |
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124 | One can control the name of the histograms file with the command: |
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125 | /testem/histo/setFileName name (default testem1) |
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126 | |
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127 | It is possible to choose the format of the histogram file (hbook, root, XML) |
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128 | with the command /testem/histo/setFileType (root by default) |
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129 | |
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130 | It is also possible to print selected histograms on an ascii file: |
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131 | /testem/histo/printHisto id |
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132 | All selected histos will be written on a file name.ascii (default testem1) |
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133 | |
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134 | Note that, by default, histograms are disabled. To activate them, uncomment |
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135 | the flag G4ANALYSIS_USE in GNUmakefile. |
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136 | |
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137 | Before compilation of the example it is optimal to clean up old files: |
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138 | gmake histclean |
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139 | gmake |
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140 | |
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141 | 9 - USING HISTOGRAMS |
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142 | |
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143 | To use histograms, at least one of the AIDA implementations should be |
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144 | available. See the file InstallAida.txt |
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145 | |
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