1 | $Id: README,v 1.13 2007/11/13 11:31:54 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 | fanoCavity |
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9 | ---------- |
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10 | |
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11 | This program computes the dose deposited in an ionization chamber by a |
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12 | monoenergetic photon beam. |
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13 | The geometry of the chamber satisfies the conditions of charged particle |
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14 | equilibrium. Hence, under idealized conditions, the ratio of the dose |
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15 | deposited over the beam energy fluence must be equal to the |
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16 | mass_energy_transfer coefficient of the wall material. |
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17 | |
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18 | E.Poon and al, Phys. Med. Biol. 50 (2005) 681 |
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19 | I.Kawrakow, Med. Phys. 27-3 (2000) 499 |
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20 | |
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21 | 1- GEOMETRY |
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22 | |
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23 | The chamber is modelized as a cylinder with a cavity in it. |
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24 | |
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25 | 6 parameters define the geometry : |
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26 | - the material of the wall of the chamber |
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27 | - the radius of the chamber and the thickness of the wall |
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28 | - the material of the cavity |
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29 | - the radius and the thickness of the cavity |
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30 | |
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31 | Wall and cavity must be made of the same material, but with different |
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32 | density |
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33 | |
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34 | All above parameters can be redifined via the UI commands built in |
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35 | DetectorMessenger class |
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36 | |
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37 | ----------------- |
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38 | | | |
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39 | | wall | |
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40 | | ----- | |
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41 | | | | | |
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42 | | | <-+-----+--- cavity |
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43 | ------> | | | | |
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44 | ------> | | | | |
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45 | beam -------------------------------- cylinder axis |
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46 | ------> | | | | |
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47 | ------> | | | | |
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48 | | | | | |
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49 | | | | | |
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50 | | ----- | |
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51 | | | |
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52 | | | |
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53 | ----------------- |
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54 | |
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55 | 2- BEAM |
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56 | |
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57 | Monoenergetic incident photon beam is uniformly distribued, perpendicular |
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58 | to the flat end of the chamber. The beam radius can be controled with an |
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59 | UI command built in PrimaryGeneratorMessenger; the default is full wall |
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60 | chamber radius. |
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61 | |
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62 | Beam regeneration : after each Compton interaction, the scattered photon is |
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63 | reset to its initial state, energy and direction. Consequently, interaction |
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64 | sites are uniformly distribued within the wall material. |
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65 | |
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66 | This modification must be done in the ParticleChange of the final state |
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67 | of the Compton scattering interaction. Therefore, a specific model |
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68 | (MyKleinNishinaCompton) is assigned to the ComptonScattering process in |
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69 | PhysicsList. MyKleinNishinaCompton inherites from G4KleinNishinaCompton; |
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70 | only the function SampleSecondaries() is overwritten. |
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71 | |
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72 | 3- PURPOSE OF THE PROGRAM |
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73 | |
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74 | The program computes the dose deposited in the cavity and the ratio |
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75 | Dose/Beam_energy_fluence. This ratio is compared to the mass_energy_transfer |
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76 | coefficient of the wall material. |
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77 | |
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78 | The mass_energy_transfer coefficient needs : |
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79 | - the photon total cross section, which is read from the PhysicsTables |
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80 | by G4EmCalculator (see EndOfRunAction). |
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81 | - the average kinetic energy of charged secondaries generated in the |
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82 | wall during the run. |
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83 | |
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84 | The program needs high statistic to reach precision on the computed dose. |
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85 | The UI command /testem/event/printModulo allows to survey the convergence of |
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86 | the kineticEnergy and dose calculations. |
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87 | |
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88 | In addition, to increase the program efficiency, the secondary particles |
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89 | which have no chance to reach the cavity are immediately killed (see |
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90 | StackinAction). This feature can be switched off by an UI command (see |
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91 | StackingMessenger). |
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92 | |
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93 | The simplest way to study the effect of e- tracking parameters on dose |
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94 | deposition is to use the command /testem/stepMax. |
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95 | |
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96 | 4- PHYSICS |
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97 | |
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98 | The physics list contains the standard electromagnetic processes, with few |
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99 | modifications listed here. |
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100 | |
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101 | - Compton scattering : as explained above, the final state is modified in |
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102 | MyKleinNishinaCompton class. |
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103 | |
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104 | In order to make the program more efficient, one can increase the Compton |
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105 | cross section via the function SetCSFactor(factor) and its |
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106 | associated UI command. Default is factor=1000. |
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107 | |
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108 | - Bremsstrahlung : Fano conditions imply no energy transfer via |
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109 | bremsstrahlung radiation. Therefore this process is not registered in the |
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110 | physics list. However, it is always possible to include it via an UI |
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111 | command. See PhysicsListMessenger class. |
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112 | |
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113 | - Ionisation : In order to have same stopping power in wall and cavity, one |
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114 | must cancel the density correction term in the dedx formula. This is done in |
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115 | a specific MollerBhabha model (MyMollerBhabhaModel) which inherites from |
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116 | G4MollerBhabhaModel. |
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117 | |
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118 | To prevent explicit generation of delta-rays, the default production |
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119 | threshold (i.e. cut) is set to 10 km (CSDA condition). |
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120 | |
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121 | The finalRange of the step function is set to 10 um, which more on less |
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122 | correspond to a tracking cut in water of about 20 keV. See emOptions. |
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123 | Once again, the above parameters can be controled via UI commands. |
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124 | |
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125 | - Multiple scattering : is switched in single Coulomb scattering mode near |
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126 | boundaries. This is selected via EM options in PhysicsList, and can be |
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127 | controled with UI commands. |
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128 | |
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129 | - All PhysicsTables are built with 100 bins per decade. |
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130 | |
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131 | 5- HISTOGRAMS |
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132 | |
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133 | fanoCavity has several predefined 1D histograms : |
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134 | |
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135 | 1 : emission point of e+- |
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136 | 2 : energy spectrum of e+- |
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137 | 3 : theta distribution of e+- |
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138 | 4 : emission point of e+- hitting cavity |
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139 | 5 : energy spectrum of e+- when entering in cavity |
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140 | 6 : theta distribution of e+- before enter in cavity |
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141 | 7 : theta distribution of e+- at first step in cavity |
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142 | 8 : track segment of e+- in cavity |
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143 | 9 : step size of e+- in wall |
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144 | 10 : step size of e+- in cavity |
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145 | 11 : energy deposit in cavity per track |
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146 | |
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147 | The histograms are managed by the HistoManager class and its Messenger. |
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148 | The histos can be individually activated with the command : |
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149 | /testem/histo/setHisto id nbBins valMin valMax unit |
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150 | where unit is the desired unit for the histo (MeV or keV, deg or mrad, etc..) |
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151 | |
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152 | One can control the name of the histograms file with the command: |
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153 | /testem/histo/setFileName name (default fanoCavity) |
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154 | |
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155 | It is possible to choose the format of the histogram file (hbook, root, XML) |
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156 | with the command /testem/histo/setFileType (hbook by default) |
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157 | |
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158 | It is also possible to print selected histograms on an ascii file: |
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159 | /testem/histo/printHisto id |
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160 | All selected histos will be written on a file name.ascii (default fanocavity) |
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161 | |
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162 | Note that, by default, histograms are disabled. To activate them, uncomment |
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163 | the flag G4ANALYSIS_USE in GNUmakefile. |
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164 | |
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165 | 6- HOW TO START ? |
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166 | |
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167 | - compile and link to generate an executable |
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168 | % cd geant4/examples/extended/medical/fanoCavity |
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169 | % gmake |
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170 | |
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171 | - execute fanoCavity in 'batch' mode from macro files |
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172 | % fanoCavity run01.mac |
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173 | |
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174 | - execute fanoCavity in 'interactive mode' with visualization |
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175 | % fanoCavity |
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176 | .... |
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177 | Idle> type your commands |
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178 | .... |
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179 | Idle> exit |
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180 | |
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181 | 7- USING HISTOGRAMS |
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182 | |
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183 | To use histograms, at least one of the AIDA implementations should be |
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184 | available (see http://aida.freehep.org). |
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185 | |
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186 | 8a - PI |
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187 | |
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188 | A package including AIDA and extended interfaces also using Python is PI, |
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189 | available from: http://cern.ch/pi |
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190 | |
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191 | Once installed PI or PI-Lite in a specified local area $MYPY, it is required |
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192 | to add the installation path to $PATH, i.e. for example, for release 1.2.1 of |
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193 | PI: |
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194 | setenv PATH ${PATH}:$MYPI/1.2.1/app/releases/PI/PI_1_2_1/rh73_gcc32/bin |
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195 | |
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196 | CERN users can use the PATH to the LCG area on AFS. |
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197 | Before running the example the command should be issued: |
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198 | eval `aida-config --runtime csh` |
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199 | |
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200 | 8b - OpenScientist |
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201 | |
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202 | OpenScientist is available at http://OpenScientist.lal.in2p3.fr. |
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203 | |
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204 | You have to "setup" the OpenScientist AIDA implementation before compiling |
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205 | (then with G4ANALYSIS_USE set) and running your Geant4 application. |
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206 | |
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207 | On UNIX you setup, with a csh flavoured shell : |
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208 | csh> source <<OpenScientist install path>/aida-setup.csh |
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209 | or with a sh flavoured shell : |
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210 | sh> . <<OpenScientist install path>/aida-setup.sh |
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211 | On Windows : |
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212 | DOS> call <<OpenScientist install path>/aida-setup.bat |
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213 | |
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214 | You can use various file formats for writing (AIDA-XML, hbook, root). |
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215 | These formats are readable by the Lab onx interactive program |
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216 | or the OpenPAW application. See the web pages. |
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217 | |
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218 | |
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219 | With OpenPAW, on a run.hbook file, one can view the histograms |
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220 | with something like : |
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221 | OS> opaw |
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222 | opaw> h/file 1 run.hbook ( or opaw> h/file 1 run.aida or run.root) |
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223 | opaw> zone 2 2 |
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224 | opaw> h/plot 1 |
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225 | opaw> h/plot 2 |
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