1 | $Id: README,v 1.6 2007/11/13 12:13:32 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 | TestEm14 |
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9 | -------- |
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10 | |
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11 | How to compute cross sections from the direct evaluation of the mean |
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12 | free path ( see below, item Physics). |
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13 | How to plot final state of a process. |
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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 'artificial' constraints on the step size, the |
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30 | multiple scattering is not instanciated, and there is no limitation from |
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31 | the maximum energy lost per step. |
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32 | |
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33 | 3- AN EVENT : THE PRIMARY GENERATOR |
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34 | |
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35 | The primary kinematic consists of a single particle starting at the edge |
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36 | of the box. The type of the particle and its energy are set in |
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37 | PrimaryGeneratorAction (1 MeV gamma), and can be changed via the G4 |
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38 | build-in commands of ParticleGun class (see the macros provided with |
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39 | this example). |
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40 | |
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41 | 4- PHYSICS |
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42 | |
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43 | An event is killed at the first interaction of the incident paticle. |
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44 | The absorption length, also called mean free path, is computed as |
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45 | the mean value of the track length of the incident particle. |
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46 | This is why the medium must be 'infinite' : to be sure that interaction |
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47 | occurs at any events. |
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48 | |
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49 | The result is compared with the 'input' data, i.e. with the cross |
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50 | sections stored in the PhysicsTables and used by Geant4. |
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51 | |
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52 | The energy spectrum and the angular distribution of the scattered |
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53 | particle (if any) and of the created secondaries are plotted (see |
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54 | SteppingAction). |
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55 | |
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56 | A set of macros defining various run conditions are provided. |
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57 | The processes are actived/inactived in order to survey the processes |
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58 | individually. |
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59 | |
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60 | 5- HISTOGRAMS |
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61 | |
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62 | The test contains 6 built-in 1D histograms, which are managed by the |
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63 | HistoManager class and its Messenger. The histos can be individually |
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64 | activated with the command : |
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65 | /testem/histo/setHisto id nbBins valMin valMax unit |
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66 | where unit is the desired unit for the histo (MeV or keV, etc..) |
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67 | (see the macros xxxx.mac). |
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68 | |
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69 | 1 "scattered primary particle: energy spectrum" |
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70 | 2 "scattered primary particle: costheta distribution" |
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71 | 3 "charged secondaries: energy spectrum" |
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72 | 4 "charged secondaries: costheta distribution" |
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73 | 5 "neutral secondaries: energy spectrum" |
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74 | 6 "neutral secondaries: costheta distribution" |
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75 | |
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76 | See below the note on histogram tools. |
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77 | |
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78 | One can control the name and the type of the histograms file with |
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79 | the commands: |
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80 | /testem/histo/setFileName name (default testem14) |
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81 | /testem/histo/setFileType name (default hbook) |
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82 | |
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83 | It is also possible to print selected histograms on an ascii file: |
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84 | /testem/histo/printHisto id |
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85 | All selected histos will be written on a file name.ascii |
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86 | (default testem14) |
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87 | |
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88 | Note that, by default, histograms are disabled. To activate them, |
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89 | uncomment the flag G4ANALYSIS_USE in GNUmakefile. |
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90 | |
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91 | 6- VISUALIZATION |
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92 | |
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93 | The Visualization Manager is set in the main(). |
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94 | The initialisation of the drawing is done via the commands |
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95 | /vis/... in the macro vis.mac. To get visualisation: |
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96 | > /control/execute vis.mac |
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97 | |
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98 | The detector has a default view which is a longitudinal view of the |
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99 | box. |
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100 | |
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101 | The tracks are drawn at the end of event, and erased at the end of run. |
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102 | |
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103 | 7- HOW TO START ? |
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104 | |
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105 | compile and link to generate an executable |
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106 | % cd geant4/examples/extended/electromagnetic/TestEm14 |
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107 | % gmake |
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108 | |
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109 | execute TestEm14 in 'batch' mode from macro files : |
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110 | % TestEm14 compt.mac |
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111 | |
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112 | execute TestEm14 in 'interactive mode' with visualization : |
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113 | % TestEm14 |
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114 | Idle> control/execute vis.mac |
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115 | .... |
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116 | Idle> type your commands |
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117 | .... |
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118 | Idle> exit |
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119 | |
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120 | |
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121 | 8- USING HISTOGRAMS |
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122 | |
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123 | By default the histograms are not activated. To activate histograms |
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124 | the environment variable G4ANALYSIS_USE should be defined. For instance |
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125 | uncomment the flag G4ANALYSIS_USE in GNUmakefile. |
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126 | |
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127 | Before compilation of the example it is optimal to clean up old files: |
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128 | gmake histclean |
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129 | gmake |
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130 | |
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131 | To use histograms, at least one of the AIDA implementations should be |
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132 | available (see http://aida.freehep.org). |
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133 | |
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134 | 8a - PI |
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135 | |
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136 | A package including AIDA and extended interfaces also using Python is PI, |
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137 | available from: http://cern.ch/pi |
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138 | |
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139 | Once installed PI or PI-Lite in a specified local area $MYPY, it is required |
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140 | to add the installation path to $PATH, i.e. for example, for release 1.2.1 of |
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141 | PI: |
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142 | setenv PATH ${PATH}:$MYPI/1.2.1/app/releases/PI/PI_1_2_1/rh73_gcc32/bin |
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143 | |
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144 | CERN users can use the PATH to the LCG area on AFS. |
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145 | Before running the example the command should be issued: |
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146 | eval `aida-config --runtime csh` |
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147 | |
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148 | 8b - OpenScientist |
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149 | |
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150 | OpenScientist is available at http://OpenScientist.lal.in2p3.fr. |
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151 | |
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152 | You have to "setup" the OpenScientist AIDA implementation before compiling |
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153 | (then with G4ANALYSIS_USE set) and running your Geant4 application. |
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154 | |
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155 | On UNIX you setup, with a csh flavoured shell : |
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156 | csh> source <<OpenScientist install path>/aida-setup.csh |
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157 | or with a sh flavoured shell : |
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158 | sh> . <<OpenScientist install path>/aida-setup.sh |
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159 | On Windows : |
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160 | DOS> call <<OpenScientist install path>/aida-setup.bat |
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161 | |
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162 | You can use various file formats for writing (AIDA-XML, hbook, root). |
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163 | These formats are readable by the Lab onx interactive program |
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164 | or the OpenPAW application. See the web pages. |
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165 | |
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166 | |
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167 | With OpenPAW, on a run.hbook file, one can view the histograms |
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168 | with something like : |
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169 | OS> opaw |
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170 | opaw> h/file 1 run.hbook ( or opaw> h/file 1 run.aida or run.root) |
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171 | opaw> zone 2 2 |
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172 | opaw> h/plot 1 |
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173 | opaw> h/plot 2 |
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