1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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14 | // * regarding this software system or assume any liability for its * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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18 | // * This code implementation is the result of the scientific and * |
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19 | // * technical work of the GEANT4 collaboration. * |
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23 | // * acceptance of all terms of the Geant4 Software license. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4LivermoreGammaConversionModel.cc,v 1.8 2009/06/11 15:47:08 mantero Exp $ |
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27 | // GEANT4 tag $Name: geant4-09-03 $ |
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28 | // |
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29 | // |
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30 | // Author: Sebastien Inserti |
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31 | // 30 October 2008 |
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32 | // |
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33 | // History: |
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34 | // -------- |
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35 | // 12 Apr 2009 V Ivanchenko Cleanup initialisation and generation of secondaries: |
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36 | // - apply internal high-energy limit only in constructor |
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37 | // - do not apply low-energy limit (default is 0) |
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38 | // - use CLHEP electron mass for low-enegry limit |
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39 | // - remove MeanFreePath method and table |
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40 | |
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41 | |
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42 | #include "G4LivermoreGammaConversionModel.hh" |
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43 | |
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44 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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45 | |
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46 | using namespace std; |
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47 | |
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48 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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49 | |
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50 | G4LivermoreGammaConversionModel::G4LivermoreGammaConversionModel(const G4ParticleDefinition*, |
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51 | const G4String& nam) |
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52 | :G4VEmModel(nam),smallEnergy(2.*MeV),isInitialised(false), |
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53 | crossSectionHandler(0),meanFreePathTable(0) |
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54 | { |
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55 | lowEnergyLimit = 2.0*electron_mass_c2; |
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56 | highEnergyLimit = 100 * GeV; |
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57 | SetHighEnergyLimit(highEnergyLimit); |
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58 | |
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59 | verboseLevel= 0; |
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60 | // Verbosity scale: |
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61 | // 0 = nothing |
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62 | // 1 = warning for energy non-conservation |
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63 | // 2 = details of energy budget |
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64 | // 3 = calculation of cross sections, file openings, sampling of atoms |
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65 | // 4 = entering in methods |
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66 | |
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67 | if(verboseLevel > 0) { |
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68 | G4cout << "Livermore Gamma conversion is constructed " << G4endl |
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69 | << "Energy range: " |
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70 | << lowEnergyLimit / MeV << " MeV - " |
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71 | << highEnergyLimit / GeV << " GeV" |
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72 | << G4endl; |
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73 | } |
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74 | } |
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75 | |
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76 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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77 | |
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78 | G4LivermoreGammaConversionModel::~G4LivermoreGammaConversionModel() |
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79 | { |
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80 | if (crossSectionHandler) delete crossSectionHandler; |
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81 | } |
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82 | |
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83 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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84 | |
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85 | void |
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86 | G4LivermoreGammaConversionModel::Initialise(const G4ParticleDefinition*, |
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87 | const G4DataVector&) |
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88 | { |
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89 | if (verboseLevel > 3) |
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90 | G4cout << "Calling G4LivermoreGammaConversionModel::Initialise()" << G4endl; |
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91 | |
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92 | if (crossSectionHandler) |
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93 | { |
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94 | crossSectionHandler->Clear(); |
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95 | delete crossSectionHandler; |
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96 | } |
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97 | |
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98 | // Read data tables for all materials |
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99 | |
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100 | crossSectionHandler = new G4CrossSectionHandler(); |
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101 | crossSectionHandler->Initialise(0,lowEnergyLimit,100.*GeV,400); |
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102 | G4String crossSectionFile = "pair/pp-cs-"; |
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103 | crossSectionHandler->LoadData(crossSectionFile); |
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104 | |
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105 | // |
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106 | |
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107 | if (verboseLevel > 2) |
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108 | G4cout << "Loaded cross section files for PenelopeGammaConversion" << G4endl; |
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109 | |
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110 | if (verboseLevel > 0) { |
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111 | G4cout << "Livermore Gamma Conversion model is initialized " << G4endl |
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112 | << "Energy range: " |
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113 | << LowEnergyLimit() / MeV << " MeV - " |
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114 | << HighEnergyLimit() / GeV << " GeV" |
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115 | << G4endl; |
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116 | } |
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117 | |
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118 | if(isInitialised) return; |
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119 | fParticleChange = GetParticleChangeForGamma(); |
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120 | isInitialised = true; |
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121 | } |
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122 | |
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123 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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124 | |
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125 | G4double |
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126 | G4LivermoreGammaConversionModel::ComputeCrossSectionPerAtom(const G4ParticleDefinition*, |
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127 | G4double GammaEnergy, |
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128 | G4double Z, G4double, |
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129 | G4double, G4double) |
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130 | { |
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131 | if (verboseLevel > 3) { |
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132 | G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreGammaConversionModel" |
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133 | << G4endl; |
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134 | } |
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135 | if (GammaEnergy < lowEnergyLimit || GammaEnergy > highEnergyLimit) return 0; |
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136 | |
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137 | G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy); |
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138 | return cs; |
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139 | } |
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140 | |
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141 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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142 | |
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143 | void G4LivermoreGammaConversionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect, |
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144 | const G4MaterialCutsCouple* couple, |
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145 | const G4DynamicParticle* aDynamicGamma, |
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146 | G4double, |
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147 | G4double) |
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148 | { |
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149 | |
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150 | // The energies of the e+ e- secondaries are sampled using the Bethe - Heitler |
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151 | // cross sections with Coulomb correction. A modified version of the random |
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152 | // number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15). |
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153 | |
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154 | // Note 1 : Effects due to the breakdown of the Born approximation at low |
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155 | // energy are ignored. |
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156 | // Note 2 : The differential cross section implicitly takes account of |
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157 | // pair creation in both nuclear and atomic electron fields. However triplet |
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158 | // prodution is not generated. |
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159 | |
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160 | if (verboseLevel > 3) |
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161 | G4cout << "Calling SampleSecondaries() of G4LivermoreGammaConversionModel" << G4endl; |
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162 | |
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163 | G4double photonEnergy = aDynamicGamma->GetKineticEnergy(); |
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164 | G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection(); |
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165 | |
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166 | G4double epsilon ; |
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167 | G4double epsilon0 = electron_mass_c2 / photonEnergy ; |
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168 | |
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169 | // Do it fast if photon energy < 2. MeV |
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170 | if (photonEnergy < smallEnergy ) |
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171 | { |
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172 | epsilon = epsilon0 + (0.5 - epsilon0) * G4UniformRand(); |
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173 | } |
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174 | else |
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175 | { |
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176 | // Select randomly one element in the current material |
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177 | //const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy); |
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178 | const G4ParticleDefinition* particle = aDynamicGamma->GetDefinition(); |
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179 | const G4Element* element = SelectRandomAtom(couple,particle,photonEnergy); |
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180 | |
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181 | if (element == 0) |
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182 | { |
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183 | G4cout << "G4LivermoreGammaConversionModel::SampleSecondaries - element = 0" |
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184 | << G4endl; |
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185 | return; |
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186 | } |
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187 | G4IonisParamElm* ionisation = element->GetIonisation(); |
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188 | if (ionisation == 0) |
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189 | { |
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190 | G4cout << "G4LivermoreGammaConversionModel::SampleSecondaries - ionisation = 0" |
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191 | << G4endl; |
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192 | return; |
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193 | } |
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194 | |
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195 | // Extract Coulomb factor for this Element |
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196 | G4double fZ = 8. * (ionisation->GetlogZ3()); |
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197 | if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb()); |
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198 | |
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199 | // Limits of the screening variable |
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200 | G4double screenFactor = 136. * epsilon0 / (element->GetIonisation()->GetZ3()) ; |
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201 | G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ; |
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202 | G4double screenMin = std::min(4.*screenFactor,screenMax) ; |
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203 | |
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204 | // Limits of the energy sampling |
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205 | G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ; |
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206 | G4double epsilonMin = std::max(epsilon0,epsilon1); |
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207 | G4double epsilonRange = 0.5 - epsilonMin ; |
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208 | |
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209 | // Sample the energy rate of the created electron (or positron) |
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210 | G4double screen; |
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211 | G4double gReject ; |
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212 | |
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213 | G4double f10 = ScreenFunction1(screenMin) - fZ; |
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214 | G4double f20 = ScreenFunction2(screenMin) - fZ; |
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215 | G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.); |
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216 | G4double normF2 = std::max(1.5 * f20,0.); |
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217 | |
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218 | do { |
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219 | if (normF1 / (normF1 + normF2) > G4UniformRand() ) |
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220 | { |
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221 | epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.3333) ; |
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222 | screen = screenFactor / (epsilon * (1. - epsilon)); |
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223 | gReject = (ScreenFunction1(screen) - fZ) / f10 ; |
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224 | } |
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225 | else |
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226 | { |
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227 | epsilon = epsilonMin + epsilonRange * G4UniformRand(); |
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228 | screen = screenFactor / (epsilon * (1 - epsilon)); |
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229 | gReject = (ScreenFunction2(screen) - fZ) / f20 ; |
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230 | } |
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231 | } while ( gReject < G4UniformRand() ); |
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232 | |
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233 | } // End of epsilon sampling |
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234 | |
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235 | // Fix charges randomly |
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236 | |
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237 | G4double electronTotEnergy; |
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238 | G4double positronTotEnergy; |
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239 | |
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240 | if (CLHEP::RandBit::shootBit()) |
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241 | { |
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242 | electronTotEnergy = (1. - epsilon) * photonEnergy; |
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243 | positronTotEnergy = epsilon * photonEnergy; |
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244 | } |
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245 | else |
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246 | { |
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247 | positronTotEnergy = (1. - epsilon) * photonEnergy; |
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248 | electronTotEnergy = epsilon * photonEnergy; |
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249 | } |
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250 | |
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251 | // Scattered electron (positron) angles. ( Z - axis along the parent photon) |
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252 | // Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211), |
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253 | // derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977) |
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254 | |
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255 | G4double u; |
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256 | const G4double a1 = 0.625; |
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257 | G4double a2 = 3. * a1; |
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258 | // G4double d = 27. ; |
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259 | |
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260 | // if (9. / (9. + d) > G4UniformRand()) |
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261 | if (0.25 > G4UniformRand()) |
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262 | { |
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263 | u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ; |
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264 | } |
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265 | else |
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266 | { |
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267 | u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ; |
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268 | } |
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269 | |
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270 | G4double thetaEle = u*electron_mass_c2/electronTotEnergy; |
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271 | G4double thetaPos = u*electron_mass_c2/positronTotEnergy; |
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272 | G4double phi = twopi * G4UniformRand(); |
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273 | |
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274 | G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle); |
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275 | G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos); |
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276 | |
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277 | |
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278 | // Kinematics of the created pair: |
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279 | // the electron and positron are assumed to have a symetric angular |
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280 | // distribution with respect to the Z axis along the parent photon |
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281 | |
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282 | G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ; |
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283 | |
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284 | // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class |
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285 | |
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286 | G4ThreeVector electronDirection (dxEle, dyEle, dzEle); |
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287 | electronDirection.rotateUz(photonDirection); |
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288 | |
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289 | G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(), |
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290 | electronDirection, |
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291 | electronKineEnergy); |
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292 | |
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293 | // The e+ is always created (even with kinetic energy = 0) for further annihilation |
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294 | G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ; |
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295 | |
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296 | // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class |
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297 | |
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298 | G4ThreeVector positronDirection (dxPos, dyPos, dzPos); |
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299 | positronDirection.rotateUz(photonDirection); |
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300 | |
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301 | // Create G4DynamicParticle object for the particle2 |
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302 | G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(), |
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303 | positronDirection, positronKineEnergy); |
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304 | // Fill output vector |
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305 | fvect->push_back(particle1); |
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306 | fvect->push_back(particle2); |
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307 | |
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308 | // kill incident photon |
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309 | fParticleChange->SetProposedKineticEnergy(0.); |
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310 | fParticleChange->ProposeTrackStatus(fStopAndKill); |
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311 | |
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312 | } |
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313 | |
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314 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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315 | |
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316 | G4double G4LivermoreGammaConversionModel::ScreenFunction1(G4double screenVariable) |
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317 | { |
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318 | // Compute the value of the screening function 3*phi1 - phi2 |
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319 | |
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320 | G4double value; |
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321 | |
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322 | if (screenVariable > 1.) |
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323 | value = 42.24 - 8.368 * std::log(screenVariable + 0.952); |
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324 | else |
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325 | value = 42.392 - screenVariable * (7.796 - 1.961 * screenVariable); |
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326 | |
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327 | return value; |
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328 | } |
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329 | |
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330 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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331 | |
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332 | G4double G4LivermoreGammaConversionModel::ScreenFunction2(G4double screenVariable) |
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333 | { |
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334 | // Compute the value of the screening function 1.5*phi1 - 0.5*phi2 |
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335 | |
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336 | G4double value; |
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337 | |
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338 | if (screenVariable > 1.) |
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339 | value = 42.24 - 8.368 * std::log(screenVariable + 0.952); |
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340 | else |
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341 | value = 41.405 - screenVariable * (5.828 - 0.8945 * screenVariable); |
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342 | |
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343 | return value; |
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344 | } |
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345 | |
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