1 | $Id: README,v 1.6 2008/09/26 19:47:51 maire 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 | TestEm15 |
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9 | -------- |
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10 | |
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11 | How to compute and plot the final state of Multiple Scattering |
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12 | considered as an isolated process. |
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13 | The method is exposed below : see item Physics. |
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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 single box representing a 'semi infinite' homogeneous medium. |
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18 | Two parameters define the geometry : |
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19 | - the material of the box, |
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20 | - the (full) size of the box. |
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21 | |
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22 | The default geometry (100 m of water) is constructed in |
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23 | DetectorConstruction, but the above parameters can be changed |
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24 | interactively via the commands defined in DetectorMessenger. |
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25 | |
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26 | 2- PHYSICS LIST |
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27 | |
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28 | The physics list contains the standard electromagnetic processes. |
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29 | In order not to introduce 'articicial' constraints on the step size, |
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30 | there is no limitation from the maximum energy lost per step. |
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31 | |
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32 | 3- AN EVENT : THE PRIMARY GENERATOR |
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33 | |
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34 | The primary kinematic consists of a single particle starting at the edge |
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35 | of the box. The type of the particle and its energy are set in |
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36 | PrimaryGeneratorAction (1 MeV electron), and can be changed via the G4 |
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37 | build-in commands of ParticleGun class (see the macros provided with |
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38 | this example). |
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39 | |
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40 | 4- PHYSICS |
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41 | |
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42 | All discrete processes are inactivated (see provided macros), |
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43 | so that Multiple Scattering is 'forced' to determine the first step of |
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44 | the primary particle. The step size and the final state are computed |
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45 | and plotted. Then the event is immediately killed. |
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46 | |
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47 | The result is compared with the 'input' data, i.e. with the cross |
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48 | sections stored in the PhysicsTables and used by Geant4. |
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49 | |
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50 | The stepMax command provides an additionnal control of the step size of |
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51 | the multiple scattering. |
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52 | |
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53 | |
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54 | 5- HISTOGRAMS |
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55 | |
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56 | The test contains 9 built-in 1D histograms, which are managed by the |
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57 | HistoManager class and its Messenger. The histos can be individually |
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58 | activated with the command : |
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59 | /testem/histo/setHisto id nbBins valMin valMax unit |
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60 | where unit is the desired unit for the histo (MeV or keV, etc..) |
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61 | (see the macros xxxx.mac). |
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62 | |
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63 | 1 Multiple Scattering. True step length |
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64 | 2 Multiple Scattering. Geom step length |
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65 | 3 Multiple Scattering. Ratio geomSl/trueSl |
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66 | 4 Multiple Scattering. Lateral displacement: radius |
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67 | 5 Multiple Scattering. Lateral displac: psi_space |
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68 | 6 Multiple Scattering. Angular distrib: theta_plane |
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69 | 7 Multiple Scattering. Phi-position angle |
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70 | 8 Multiple Scattering. Phi-direction angle |
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71 | 9 Multiple Scattering. Correlation: cos(phiPos-phiDir) |
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72 | |
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73 | See below the note on histogram tools. |
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74 | |
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75 | One can control the name and the type of the histograms file with |
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76 | the commands: |
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77 | /testem/histo/setFileName name (default testem15) |
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78 | /testem/histo/setFileType name (default root) |
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79 | |
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80 | It is also possible to print selected histograms on an ascii file: |
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81 | /testem/histo/printHisto id |
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82 | All selected histos will be written on a file name.ascii |
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83 | (default testem15) |
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84 | |
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85 | Note that, by default, histograms are disabled. To activate them, |
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86 | uncomment the flag G4ANALYSIS_USE in GNUmakefile. |
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87 | |
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88 | 6- VISUALIZATION |
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89 | |
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90 | The Visualization Manager is set in the main(). |
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91 | The initialisation of the drawing is done via the commands |
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92 | /vis/... in the macro vis.mac. To get visualisation: |
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93 | > /control/execute vis.mac |
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94 | |
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95 | The detector has a default view which is a longitudinal view of the |
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96 | box. |
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97 | |
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98 | The tracks are drawn at the end of event, and erased at the end of run. |
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99 | |
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100 | 7- HOW TO START ? |
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101 | |
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102 | compile and link to generate an executable |
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103 | % cd geant4/examples/extended/electromagnetic/TestEm15 |
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104 | % gmake |
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105 | |
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106 | execute TestEm15 in 'batch' mode from macro files : |
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107 | % TestEm15 compt.mac |
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108 | |
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109 | execute TestEm15 in 'interactive mode' with visualization : |
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110 | % TestEm15 |
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111 | Idle> control/execute vis.mac |
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112 | .... |
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113 | Idle> type your commands |
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114 | .... |
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115 | Idle> exit |
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116 | |
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117 | |
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118 | 8- USING HISTOGRAMS |
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119 | |
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120 | By default the histograms are not activated. To activate histograms |
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121 | the environment variable G4ANALYSIS_USE should be defined. For instance |
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122 | uncomment the flag G4ANALYSIS_USE in GNUmakefile. |
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123 | |
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124 | Before compilation of the example it is optimal to clean up old files: |
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125 | gmake histclean |
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126 | gmake |
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127 | |
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128 | To use histograms, at least one of the AIDA implementations should be |
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129 | available. See InstallAida.txt |
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