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2 | // ******************************************************************** |
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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4eBremsstrahlungModel.cc,v 1.44 2009/04/09 18:41:18 vnivanch Exp $ |
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27 | // GEANT4 tag $Name: geant4-09-03-beta-cand-01 $ |
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28 | // |
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29 | // ------------------------------------------------------------------- |
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30 | // |
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31 | // GEANT4 Class file |
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32 | // |
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33 | // |
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34 | // File name: G4eBremsstrahlungModel |
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35 | // |
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36 | // Author: Vladimir Ivanchenko on base of Laszlo Urban code |
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37 | // |
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38 | // Creation date: 03.01.2002 |
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39 | // |
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40 | // Modifications: |
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41 | // |
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42 | // 11-11-02 Fix division by 0 (V.Ivanchenko) |
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43 | // 04-12-02 Change G4DynamicParticle constructor in PostStep (V.Ivanchenko) |
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44 | // 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko) |
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45 | // 24-01-03 Fix for compounds (V.Ivanchenko) |
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46 | // 27-01-03 Make models region aware (V.Ivanchenko) |
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47 | // 13-02-03 Add name (V.Ivanchenko) |
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48 | // 09-05-03 Fix problem of supression function + optimise sampling (V.Ivanchenko) |
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49 | // 20-05-04 Correction to ensure unit independence (L.Urban) |
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50 | // 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko) |
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51 | // 03-08-05 Add extra protection at initialisation (V.Ivantchenko) |
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52 | // 07-02-06 public function ComputeCrossSectionPerAtom() (mma) |
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53 | // 21-03-06 Fix problem of initialisation in case when cuts are not defined (VI) |
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54 | // 27-03-06 Fix calculation of fl parameter at low energy (energy loss) (VI) |
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55 | // 15-02-07 correct LPMconstant by a factor 2, thanks to G. Depaola (mma) |
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56 | // 09-09-08 MigdalConstant increased in (2pi)^2 times (A.Schaelicke) |
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57 | // |
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58 | // Class Description: |
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59 | // |
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60 | // |
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61 | // ------------------------------------------------------------------- |
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62 | // |
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63 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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64 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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65 | |
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66 | #include "G4eBremsstrahlungModel.hh" |
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67 | #include "G4Electron.hh" |
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68 | #include "G4Positron.hh" |
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69 | #include "G4Gamma.hh" |
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70 | #include "Randomize.hh" |
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71 | #include "G4Material.hh" |
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72 | #include "G4Element.hh" |
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73 | #include "G4ElementVector.hh" |
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74 | #include "G4ProductionCutsTable.hh" |
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75 | #include "G4DataVector.hh" |
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76 | #include "G4ParticleChangeForLoss.hh" |
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77 | |
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78 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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79 | |
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80 | using namespace std; |
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81 | |
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82 | G4eBremsstrahlungModel::G4eBremsstrahlungModel(const G4ParticleDefinition* p, |
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83 | const G4String& nam) |
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84 | : G4VEmModel(nam), |
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85 | particle(0), |
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86 | isElectron(true), |
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87 | probsup(1.0), |
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88 | MigdalConstant(classic_electr_radius*electron_Compton_length*electron_Compton_length*4.0*pi), |
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89 | LPMconstant(fine_structure_const*electron_mass_c2*electron_mass_c2/(4.*pi*hbarc)), |
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90 | isInitialised(false) |
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91 | { |
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92 | if(p) SetParticle(p); |
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93 | theGamma = G4Gamma::Gamma(); |
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94 | minThreshold = 1.0*keV; |
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95 | } |
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96 | |
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97 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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98 | |
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99 | G4eBremsstrahlungModel::~G4eBremsstrahlungModel() |
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100 | { |
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101 | size_t n = partialSumSigma.size(); |
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102 | if(n > 0) { |
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103 | for(size_t i=0; i<n; i++) { |
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104 | delete partialSumSigma[i]; |
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105 | } |
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106 | } |
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107 | } |
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108 | |
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109 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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110 | |
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111 | void G4eBremsstrahlungModel::SetParticle(const G4ParticleDefinition* p) |
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112 | { |
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113 | particle = p; |
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114 | if(p == G4Electron::Electron()) isElectron = true; |
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115 | else isElectron = false; |
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116 | } |
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117 | |
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118 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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119 | |
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120 | G4double G4eBremsstrahlungModel::MinEnergyCut(const G4ParticleDefinition*, |
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121 | const G4MaterialCutsCouple*) |
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122 | { |
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123 | return minThreshold; |
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124 | } |
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125 | |
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126 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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127 | |
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128 | void G4eBremsstrahlungModel::Initialise(const G4ParticleDefinition* p, |
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129 | const G4DataVector& cuts) |
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130 | { |
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131 | if(p) SetParticle(p); |
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132 | highKinEnergy = HighEnergyLimit(); |
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133 | lowKinEnergy = LowEnergyLimit(); |
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134 | const G4ProductionCutsTable* theCoupleTable= |
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135 | G4ProductionCutsTable::GetProductionCutsTable(); |
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136 | |
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137 | if(theCoupleTable) { |
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138 | G4int numOfCouples = theCoupleTable->GetTableSize(); |
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139 | |
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140 | G4int nn = partialSumSigma.size(); |
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141 | G4int nc = cuts.size(); |
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142 | if(nn > 0) { |
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143 | for (G4int ii=0; ii<nn; ii++){ |
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144 | G4DataVector* a=partialSumSigma[ii]; |
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145 | if ( a ) delete a; |
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146 | } |
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147 | partialSumSigma.clear(); |
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148 | } |
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149 | if(numOfCouples>0) { |
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150 | for (G4int i=0; i<numOfCouples; i++) { |
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151 | G4double cute = DBL_MAX; |
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152 | if(i < nc) cute = cuts[i]; |
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153 | const G4MaterialCutsCouple* couple = theCoupleTable->GetMaterialCutsCouple(i); |
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154 | const G4Material* material = couple->GetMaterial(); |
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155 | G4DataVector* dv = ComputePartialSumSigma(material, 0.5*highKinEnergy, |
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156 | std::min(cute, 0.25*highKinEnergy)); |
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157 | partialSumSigma.push_back(dv); |
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158 | } |
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159 | } |
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160 | } |
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161 | if(isInitialised) return; |
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162 | fParticleChange = GetParticleChangeForLoss(); |
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163 | isInitialised = true; |
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164 | } |
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165 | |
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166 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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167 | |
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168 | G4double G4eBremsstrahlungModel::ComputeDEDXPerVolume( |
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169 | const G4Material* material, |
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170 | const G4ParticleDefinition* p, |
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171 | G4double kineticEnergy, |
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172 | G4double cutEnergy) |
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173 | { |
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174 | if(!particle) SetParticle(p); |
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175 | if(kineticEnergy < lowKinEnergy) return 0.0; |
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176 | |
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177 | const G4double thigh = 100.*GeV; |
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178 | |
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179 | G4double cut = std::min(cutEnergy, kineticEnergy); |
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180 | |
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181 | G4double rate, loss; |
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182 | const G4double factorHigh = 36./(1450.*GeV); |
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183 | const G4double coef1 = -0.5; |
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184 | const G4double coef2 = 2./9.; |
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185 | |
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186 | const G4ElementVector* theElementVector = material->GetElementVector(); |
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187 | const G4double* theAtomicNumDensityVector = material->GetAtomicNumDensityVector(); |
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188 | |
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189 | G4double totalEnergy = kineticEnergy + electron_mass_c2; |
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190 | G4double dedx = 0.0; |
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191 | |
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192 | // loop for elements in the material |
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193 | for (size_t i=0; i<material->GetNumberOfElements(); i++) { |
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194 | |
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195 | G4double Z = (*theElementVector)[i]->GetZ(); |
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196 | G4double natom = theAtomicNumDensityVector[i]; |
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197 | |
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198 | // loss for MinKinEnergy<KineticEnergy<=100 GeV |
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199 | if (kineticEnergy <= thigh) { |
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200 | |
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201 | // x = log(totalEnergy/electron_mass_c2); |
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202 | loss = ComputeBremLoss(Z, kineticEnergy, cut) ; |
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203 | if (!isElectron) loss *= PositronCorrFactorLoss(Z, kineticEnergy, cut); |
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204 | |
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205 | // extrapolation for KineticEnergy>100 GeV |
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206 | } else { |
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207 | |
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208 | // G4double xhigh = log(thigh/electron_mass_c2); |
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209 | G4double cuthigh = thigh*0.5; |
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210 | |
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211 | if (cut < thigh) { |
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212 | |
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213 | loss = ComputeBremLoss(Z, thigh, cut) ; |
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214 | if (!isElectron) loss *= PositronCorrFactorLoss(Z, thigh, cut) ; |
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215 | rate = cut/totalEnergy; |
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216 | loss *= (1. + coef1*rate + coef2*rate*rate); |
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217 | rate = cut/thigh; |
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218 | loss /= (1.+coef1*rate+coef2*rate*rate); |
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219 | |
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220 | } else { |
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221 | |
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222 | loss = ComputeBremLoss(Z, thigh, cuthigh) ; |
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223 | if (!isElectron) loss *= PositronCorrFactorLoss(Z, thigh, cuthigh) ; |
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224 | rate = cut/totalEnergy; |
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225 | loss *= (1. + coef1*rate + coef2*rate*rate); |
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226 | loss *= cut*factorHigh; |
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227 | } |
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228 | } |
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229 | loss *= natom; |
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230 | |
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231 | G4double kp2 = MigdalConstant*totalEnergy*totalEnergy |
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232 | * (material->GetElectronDensity()) ; |
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233 | |
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234 | // now compute the correction due to the supression(s) |
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235 | G4double kmin = 1.*eV; |
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236 | G4double kmax = cut; |
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237 | |
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238 | if (kmax > kmin) { |
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239 | |
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240 | G4double floss = 0.; |
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241 | G4int nmax = 100; |
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242 | |
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243 | G4double vmin=log(kmin); |
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244 | G4double vmax=log(kmax) ; |
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245 | G4int nn = (G4int)(nmax*(vmax-vmin)/(log(highKinEnergy)-vmin)) ; |
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246 | G4double u,fac,c,v,dv ; |
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247 | if(nn > 0) { |
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248 | |
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249 | dv = (vmax-vmin)/nn ; |
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250 | v = vmin-dv ; |
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251 | |
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252 | for(G4int n=0; n<=nn; n++) { |
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253 | |
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254 | v += dv; |
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255 | u = exp(v); |
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256 | fac = u*SupressionFunction(material,kineticEnergy,u); |
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257 | fac *= probsup*(u*u/(u*u+kp2))+1.-probsup; |
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258 | if ((n==0)||(n==nn)) c=0.5; |
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259 | else c=1. ; |
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260 | fac *= c ; |
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261 | floss += fac ; |
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262 | } |
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263 | floss *=dv/(kmax-kmin); |
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264 | |
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265 | } else { |
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266 | floss = 1.; |
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267 | } |
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268 | if(floss > 1.) floss = 1.; |
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269 | // correct the loss |
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270 | loss *= floss; |
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271 | } |
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272 | dedx += loss; |
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273 | } |
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274 | if(dedx < 0.) dedx = 0.; |
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275 | return dedx; |
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276 | } |
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277 | |
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278 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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279 | |
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280 | G4double G4eBremsstrahlungModel::ComputeBremLoss(G4double Z, G4double T, |
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281 | G4double Cut) |
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282 | |
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283 | // compute loss due to soft brems |
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284 | { |
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285 | static const G4double beta=1.0, ksi=2.0; |
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286 | static const G4double clossh = 0.254 , closslow = 1./3. , alosslow = 1. ; |
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287 | static const G4double Tlim= 10.*MeV ; |
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288 | |
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289 | static const G4double xlim = 1.2 ; |
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290 | static const G4int NZ = 8 ; |
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291 | static const G4int Nloss = 11 ; |
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292 | static const G4double ZZ[NZ] = |
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293 | {2.,4.,6.,14.,26.,50.,82.,92.}; |
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294 | static const G4double coefloss[NZ][Nloss] = { |
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295 | // Z=2 |
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296 | { 0.98916, 0.47564, -0.2505, -0.45186, 0.14462, |
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297 | 0.21307, -0.013738, -0.045689, -0.0042914, 0.0034429, |
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298 | 0.00064189}, |
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299 | |
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300 | // Z=4 |
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301 | { 1.0626, 0.37662, -0.23646, -0.45188, 0.14295, |
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302 | 0.22906, -0.011041, -0.051398, -0.0055123, 0.0039919, |
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303 | 0.00078003}, |
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304 | // Z=6 |
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305 | { 1.0954, 0.315, -0.24011, -0.43849, 0.15017, |
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306 | 0.23001, -0.012846, -0.052555, -0.0055114, 0.0041283, |
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307 | 0.00080318}, |
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308 | |
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309 | // Z=14 |
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310 | { 1.1649, 0.18976, -0.24972, -0.30124, 0.1555, |
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311 | 0.13565, -0.024765, -0.027047, -0.00059821, 0.0019373, |
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312 | 0.00027647}, |
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313 | |
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314 | // Z=26 |
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315 | { 1.2261, 0.14272, -0.25672, -0.28407, 0.13874, |
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316 | 0.13586, -0.020562, -0.026722, -0.00089557, 0.0018665, |
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317 | 0.00026981}, |
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318 | |
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319 | // Z=50 |
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320 | { 1.3147, 0.020049, -0.35543, -0.13927, 0.17666, |
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321 | 0.073746, -0.036076, -0.013407, 0.0025727, 0.00084005, |
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322 | -1.4082e-05}, |
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323 | |
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324 | // Z=82 |
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325 | { 1.3986, -0.10586, -0.49187, -0.0048846, 0.23621, |
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326 | 0.031652, -0.052938, -0.0076639, 0.0048181, 0.00056486, |
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327 | -0.00011995}, |
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328 | |
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329 | // Z=92 |
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330 | { 1.4217, -0.116, -0.55497, -0.044075, 0.27506, |
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331 | 0.081364, -0.058143, -0.023402, 0.0031322, 0.0020201, |
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332 | 0.00017519} |
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333 | |
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334 | } ; |
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335 | static G4double aaa = 0.414; |
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336 | static G4double bbb = 0.345; |
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337 | static G4double ccc = 0.460; |
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338 | |
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339 | G4int iz = 0; |
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340 | G4double delz = 1.e6; |
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341 | for (G4int ii=0; ii<NZ; ii++) |
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342 | { |
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343 | G4double dz = std::abs(Z-ZZ[ii]); |
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344 | if(dz < delz) { |
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345 | iz = ii; |
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346 | delz = dz; |
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347 | } |
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348 | } |
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349 | |
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350 | G4double xx = log10(T/MeV); |
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351 | G4double fl = 1.; |
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352 | |
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353 | if (xx <= xlim) |
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354 | { |
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355 | xx /= xlim; |
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356 | G4double yy = 1.0; |
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357 | fl = 0.0; |
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358 | for (G4int j=0; j<Nloss; j++) { |
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359 | fl += yy+coefloss[iz][j]; |
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360 | yy *= xx; |
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361 | } |
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362 | if (fl < 0.00001) fl = 0.00001; |
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363 | else if (fl > 1.0) fl = 1.0; |
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364 | } |
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365 | |
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366 | G4double loss; |
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367 | G4double E = T+electron_mass_c2 ; |
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368 | |
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369 | loss = Z*(Z+ksi)*E*E/(T+E)*exp(beta*log(Cut/T))*(2.-clossh*exp(log(Z)/4.)); |
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370 | if (T <= Tlim) loss /= exp(closslow*log(Tlim/T)); |
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371 | if( T <= Cut) loss *= exp(alosslow*log(T/Cut)); |
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372 | // correction |
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373 | loss *= (aaa+bbb*T/Tlim)/(1.+ccc*T/Tlim); |
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374 | loss *= fl; |
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375 | loss /= Avogadro; |
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376 | |
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377 | return loss; |
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378 | } |
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379 | |
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380 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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381 | |
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382 | G4double G4eBremsstrahlungModel::PositronCorrFactorLoss(G4double Z, |
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383 | G4double kineticEnergy, G4double cut) |
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384 | |
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385 | //calculates the correction factor for the energy loss due to bremsstrahlung for positrons |
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386 | //the same correction is in the (discrete) bremsstrahlung |
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387 | |
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388 | { |
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389 | static const G4double K = 132.9416*eV ; |
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390 | static const G4double a1=4.15e-1, a3=2.10e-3, a5=54.0e-5 ; |
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391 | |
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392 | G4double x = log(kineticEnergy/(K*Z*Z)), x2 = x*x, x3 = x2*x; |
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393 | G4double eta = 0.5+atan(a1*x+a3*x3+a5*x3*x2)/pi; |
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394 | G4double e0 = cut/kineticEnergy; |
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395 | |
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396 | G4double factor = 0.0; |
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397 | if (e0 < 1.0) { |
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398 | factor=log(1.-e0)/eta; |
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399 | factor=exp(factor); |
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400 | } |
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401 | factor = eta*(1.-factor)/e0; |
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402 | |
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403 | return factor; |
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404 | } |
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405 | |
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406 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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407 | |
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408 | G4double G4eBremsstrahlungModel::CrossSectionPerVolume( |
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409 | const G4Material* material, |
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410 | const G4ParticleDefinition* p, |
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411 | G4double kineticEnergy, |
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412 | G4double cutEnergy, |
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413 | G4double maxEnergy) |
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414 | { |
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415 | if(!particle) SetParticle(p); |
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416 | G4double cross = 0.0; |
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417 | G4double tmax = min(maxEnergy, kineticEnergy); |
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418 | G4double cut = max(cutEnergy, minThreshold); |
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419 | if(cut >= tmax) return cross; |
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420 | |
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421 | const G4ElementVector* theElementVector = material->GetElementVector(); |
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422 | const G4double* theAtomNumDensityVector = material->GetAtomicNumDensityVector(); |
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423 | G4double dum=0.; |
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424 | |
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425 | for (size_t i=0; i<material->GetNumberOfElements(); i++) { |
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426 | |
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427 | cross += theAtomNumDensityVector[i] * ComputeCrossSectionPerAtom(p, |
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428 | kineticEnergy, (*theElementVector)[i]->GetZ(), dum, cut); |
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429 | if (tmax < kineticEnergy) { |
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430 | cross -= theAtomNumDensityVector[i] * ComputeCrossSectionPerAtom(p, |
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431 | kineticEnergy, (*theElementVector)[i]->GetZ(), dum, tmax); |
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432 | } |
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433 | } |
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434 | |
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435 | // now compute the correction due to the supression(s) |
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436 | |
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437 | G4double kmax = tmax; |
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438 | G4double kmin = cut; |
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439 | |
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440 | G4double totalEnergy = kineticEnergy+electron_mass_c2 ; |
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441 | G4double kp2 = MigdalConstant*totalEnergy*totalEnergy |
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442 | *(material->GetElectronDensity()); |
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443 | |
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444 | G4double fsig = 0.; |
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445 | G4int nmax = 100; |
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446 | G4double vmin=log(kmin); |
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447 | G4double vmax=log(kmax) ; |
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448 | G4int nn = (G4int)(nmax*(vmax-vmin)/(log(highKinEnergy)-vmin)); |
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449 | G4double u,fac,c,v,dv,y ; |
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450 | if(nn > 0) { |
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451 | |
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452 | dv = (vmax-vmin)/nn ; |
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453 | v = vmin-dv ; |
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454 | for(G4int n=0; n<=nn; n++) { |
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455 | |
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456 | v += dv; |
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457 | u = exp(v); |
---|
458 | fac = SupressionFunction(material, kineticEnergy, u); |
---|
459 | y = u/kmax; |
---|
460 | fac *= (4.-4.*y+3.*y*y)/3.; |
---|
461 | fac *= probsup*(u*u/(u*u+kp2))+1.-probsup; |
---|
462 | |
---|
463 | if ((n==0)||(n==nn)) c=0.5; |
---|
464 | else c=1. ; |
---|
465 | |
---|
466 | fac *= c; |
---|
467 | fsig += fac; |
---|
468 | } |
---|
469 | y = kmin/kmax ; |
---|
470 | fsig *=dv/(-4.*log(y)/3.-4.*(1.-y)/3.+0.5*(1.-y*y)); |
---|
471 | |
---|
472 | } else { |
---|
473 | |
---|
474 | fsig = 1.; |
---|
475 | } |
---|
476 | if (fsig > 1.) fsig = 1.; |
---|
477 | |
---|
478 | // correct the cross section |
---|
479 | cross *= fsig; |
---|
480 | |
---|
481 | return cross; |
---|
482 | } |
---|
483 | |
---|
484 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
---|
485 | |
---|
486 | G4double G4eBremsstrahlungModel::ComputeCrossSectionPerAtom( |
---|
487 | const G4ParticleDefinition*, |
---|
488 | G4double kineticEnergy, |
---|
489 | G4double Z, G4double, |
---|
490 | G4double cut, G4double) |
---|
491 | |
---|
492 | // Calculates the cross section per atom in GEANT4 internal units. |
---|
493 | // |
---|
494 | |
---|
495 | { |
---|
496 | G4double cross = 0.0 ; |
---|
497 | if ( kineticEnergy < 1*keV || kineticEnergy < cut) return cross; |
---|
498 | |
---|
499 | static const G4double ksi=2.0, alfa=1.00; |
---|
500 | static const G4double csigh = 0.127, csiglow = 0.25, asiglow = 0.020*MeV ; |
---|
501 | static const G4double Tlim = 10.*MeV ; |
---|
502 | |
---|
503 | static const G4double xlim = 1.2 ; |
---|
504 | static const G4int NZ = 8 ; |
---|
505 | static const G4int Nsig = 11 ; |
---|
506 | static const G4double ZZ[NZ] = |
---|
507 | {2.,4.,6.,14.,26.,50.,82.,92.} ; |
---|
508 | static const G4double coefsig[NZ][Nsig] = { |
---|
509 | // Z=2 |
---|
510 | { 0.4638, 0.37748, 0.32249, -0.060362, -0.065004, |
---|
511 | -0.033457, -0.004583, 0.011954, 0.0030404, -0.0010077, |
---|
512 | -0.00028131}, |
---|
513 | |
---|
514 | // Z=4 |
---|
515 | { 0.50008, 0.33483, 0.34364, -0.086262, -0.055361, |
---|
516 | -0.028168, -0.0056172, 0.011129, 0.0027528, -0.00092265, |
---|
517 | -0.00024348}, |
---|
518 | |
---|
519 | // Z=6 |
---|
520 | { 0.51587, 0.31095, 0.34996, -0.11623, -0.056167, |
---|
521 | -0.0087154, 0.00053943, 0.0054092, 0.00077685, -0.00039635, |
---|
522 | -6.7818e-05}, |
---|
523 | |
---|
524 | // Z=14 |
---|
525 | { 0.55058, 0.25629, 0.35854, -0.080656, -0.054308, |
---|
526 | -0.049933, -0.00064246, 0.016597, 0.0021789, -0.001327, |
---|
527 | -0.00025983}, |
---|
528 | |
---|
529 | // Z=26 |
---|
530 | { 0.5791, 0.26152, 0.38953, -0.17104, -0.099172, |
---|
531 | 0.024596, 0.023718, -0.0039205, -0.0036658, 0.00041749, |
---|
532 | 0.00023408}, |
---|
533 | |
---|
534 | // Z=50 |
---|
535 | { 0.62085, 0.27045, 0.39073, -0.37916, -0.18878, |
---|
536 | 0.23905, 0.095028, -0.068744, -0.023809, 0.0062408, |
---|
537 | 0.0020407}, |
---|
538 | |
---|
539 | // Z=82 |
---|
540 | { 0.66053, 0.24513, 0.35404, -0.47275, -0.22837, |
---|
541 | 0.35647, 0.13203, -0.1049, -0.034851, 0.0095046, |
---|
542 | 0.0030535}, |
---|
543 | |
---|
544 | // Z=92 |
---|
545 | { 0.67143, 0.23079, 0.32256, -0.46248, -0.20013, |
---|
546 | 0.3506, 0.11779, -0.1024, -0.032013, 0.0092279, |
---|
547 | 0.0028592} |
---|
548 | |
---|
549 | } ; |
---|
550 | |
---|
551 | G4int iz = 0 ; |
---|
552 | G4double delz = 1.e6 ; |
---|
553 | for (G4int ii=0; ii<NZ; ii++) |
---|
554 | { |
---|
555 | G4double absdelz = std::abs(Z-ZZ[ii]); |
---|
556 | if(absdelz < delz) |
---|
557 | { |
---|
558 | iz = ii ; |
---|
559 | delz = absdelz; |
---|
560 | } |
---|
561 | } |
---|
562 | |
---|
563 | G4double xx = log10(kineticEnergy/MeV) ; |
---|
564 | G4double fs = 1. ; |
---|
565 | |
---|
566 | if (xx <= xlim) { |
---|
567 | |
---|
568 | fs = coefsig[iz][Nsig-1] ; |
---|
569 | for (G4int j=Nsig-2; j>=0; j--) { |
---|
570 | |
---|
571 | fs = fs*xx+coefsig[iz][j] ; |
---|
572 | } |
---|
573 | if(fs < 0.) fs = 0.; |
---|
574 | } |
---|
575 | |
---|
576 | cross = Z*(Z+ksi)*(1.-csigh*exp(log(Z)/4.))*pow(log(kineticEnergy/cut),alfa); |
---|
577 | |
---|
578 | if (kineticEnergy <= Tlim) |
---|
579 | cross *= exp(csiglow*log(Tlim/kineticEnergy)) |
---|
580 | *(1.+asiglow/(sqrt(Z)*kineticEnergy)); |
---|
581 | |
---|
582 | if (!isElectron) |
---|
583 | cross *= PositronCorrFactorSigma(Z, kineticEnergy, cut); |
---|
584 | |
---|
585 | cross *= fs/Avogadro ; |
---|
586 | |
---|
587 | if (cross < 0.) cross = 0.; |
---|
588 | return cross; |
---|
589 | } |
---|
590 | |
---|
591 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
---|
592 | |
---|
593 | G4double G4eBremsstrahlungModel::PositronCorrFactorSigma( G4double Z, |
---|
594 | G4double kineticEnergy, G4double cut) |
---|
595 | |
---|
596 | //Calculates the correction factor for the total cross section of the positron |
---|
597 | // bremsstrahl. |
---|
598 | // Eta is the ratio of positron to electron energy loss by bremstrahlung. |
---|
599 | // A parametrized formula from L. Urban is used to estimate eta. It is a fit to |
---|
600 | // the results of L. Kim & al: Phys Rev. A33,3002 (1986) |
---|
601 | |
---|
602 | { |
---|
603 | static const G4double K = 132.9416*eV; |
---|
604 | static const G4double a1 = 4.15e-1, a3 = 2.10e-3, a5 = 54.0e-5; |
---|
605 | |
---|
606 | G4double x = log(kineticEnergy/(K*Z*Z)); |
---|
607 | G4double x2 = x*x; |
---|
608 | G4double x3 = x2*x; |
---|
609 | G4double eta = 0.5 + atan(a1*x + a3*x3 + a5*x3*x2)/pi ; |
---|
610 | G4double alfa = (1. - eta)/eta; |
---|
611 | return eta*pow((1. - cut/kineticEnergy), alfa); |
---|
612 | } |
---|
613 | |
---|
614 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
---|
615 | |
---|
616 | G4DataVector* G4eBremsstrahlungModel::ComputePartialSumSigma( |
---|
617 | const G4Material* material, |
---|
618 | G4double kineticEnergy, |
---|
619 | G4double cut) |
---|
620 | |
---|
621 | // Build the table of cross section per element. |
---|
622 | //The table is built for MATERIALS. |
---|
623 | // This table is used by DoIt to select randomly an element in the material. |
---|
624 | { |
---|
625 | G4int nElements = material->GetNumberOfElements(); |
---|
626 | const G4ElementVector* theElementVector = material->GetElementVector(); |
---|
627 | const G4double* theAtomNumDensityVector = material->GetAtomicNumDensityVector(); |
---|
628 | G4double dum = 0.; |
---|
629 | |
---|
630 | G4DataVector* dv = new G4DataVector(); |
---|
631 | |
---|
632 | G4double cross = 0.0; |
---|
633 | |
---|
634 | for (G4int i=0; i<nElements; i++ ) { |
---|
635 | |
---|
636 | cross += theAtomNumDensityVector[i] * ComputeCrossSectionPerAtom( particle, |
---|
637 | kineticEnergy, (*theElementVector)[i]->GetZ(), dum, cut); |
---|
638 | dv->push_back(cross); |
---|
639 | } |
---|
640 | return dv; |
---|
641 | } |
---|
642 | |
---|
643 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
---|
644 | |
---|
645 | void G4eBremsstrahlungModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp, |
---|
646 | const G4MaterialCutsCouple* couple, |
---|
647 | const G4DynamicParticle* dp, |
---|
648 | G4double tmin, |
---|
649 | G4double maxEnergy) |
---|
650 | // The emitted gamma energy is sampled using a parametrized formula |
---|
651 | // from L. Urban. |
---|
652 | // This parametrization is derived from : |
---|
653 | // cross-section values of Seltzer and Berger for electron energies |
---|
654 | // 1 keV - 10 GeV, |
---|
655 | // screened Bethe Heilter differential cross section above 10 GeV, |
---|
656 | // Migdal corrections in both case. |
---|
657 | // Seltzer & Berger: Nim B 12:95 (1985) |
---|
658 | // Nelson, Hirayama & Rogers: Technical report 265 SLAC (1985) |
---|
659 | // Migdal: Phys Rev 103:1811 (1956); Messel & Crawford: Pergamon Press (1970) |
---|
660 | // |
---|
661 | // A modified version of the random number techniques of Butcher&Messel is used |
---|
662 | // (Nuc Phys 20(1960),15). |
---|
663 | { |
---|
664 | G4double kineticEnergy = dp->GetKineticEnergy(); |
---|
665 | G4double tmax = min(maxEnergy, kineticEnergy); |
---|
666 | if(tmin >= tmax) return; |
---|
667 | |
---|
668 | // |
---|
669 | // GEANT4 internal units. |
---|
670 | // |
---|
671 | static const G4double |
---|
672 | ah10 = 4.67733E+00, ah11 =-6.19012E-01, ah12 = 2.02225E-02, |
---|
673 | ah20 =-7.34101E+00, ah21 = 1.00462E+00, ah22 =-3.20985E-02, |
---|
674 | ah30 = 2.93119E+00, ah31 =-4.03761E-01, ah32 = 1.25153E-02; |
---|
675 | |
---|
676 | static const G4double |
---|
677 | bh10 = 4.23071E+00, bh11 =-6.10995E-01, bh12 = 1.95531E-02, |
---|
678 | bh20 =-7.12527E+00, bh21 = 9.69160E-01, bh22 =-2.74255E-02, |
---|
679 | bh30 = 2.69925E+00, bh31 =-3.63283E-01, bh32 = 9.55316E-03; |
---|
680 | |
---|
681 | static const G4double |
---|
682 | al00 =-2.05398E+00, al01 = 2.38815E-02, al02 = 5.25483E-04, |
---|
683 | al10 =-7.69748E-02, al11 =-6.91499E-02, al12 = 2.22453E-03, |
---|
684 | al20 = 4.06463E-02, al21 =-1.01281E-02, al22 = 3.40919E-04; |
---|
685 | |
---|
686 | static const G4double |
---|
687 | bl00 = 1.04133E+00, bl01 =-9.43291E-03, bl02 =-4.54758E-04, |
---|
688 | bl10 = 1.19253E-01, bl11 = 4.07467E-02, bl12 =-1.30718E-03, |
---|
689 | bl20 =-1.59391E-02, bl21 = 7.27752E-03, bl22 =-1.94405E-04; |
---|
690 | |
---|
691 | static const G4double tlow = 1.*MeV; |
---|
692 | |
---|
693 | G4double gammaEnergy; |
---|
694 | G4bool LPMOK = false; |
---|
695 | const G4Material* material = couple->GetMaterial(); |
---|
696 | |
---|
697 | // select randomly one element constituing the material |
---|
698 | const G4Element* anElement = SelectRandomAtom(couple); |
---|
699 | |
---|
700 | // Extract Z factors for this Element |
---|
701 | G4double lnZ = 3.*(anElement->GetIonisation()->GetlogZ3()); |
---|
702 | G4double FZ = lnZ* (4.- 0.55*lnZ); |
---|
703 | G4double ZZ = anElement->GetIonisation()->GetZZ3(); |
---|
704 | |
---|
705 | // limits of the energy sampling |
---|
706 | G4double totalEnergy = kineticEnergy + electron_mass_c2; |
---|
707 | G4ThreeVector direction = dp->GetMomentumDirection(); |
---|
708 | G4double xmin = tmin/kineticEnergy; |
---|
709 | G4double xmax = tmax/kineticEnergy; |
---|
710 | G4double kappa = 0.0; |
---|
711 | if(xmax >= 1.) xmax = 1.; |
---|
712 | else kappa = log(xmax)/log(xmin); |
---|
713 | G4double epsilmin = tmin/totalEnergy; |
---|
714 | G4double epsilmax = tmax/totalEnergy; |
---|
715 | |
---|
716 | // Migdal factor |
---|
717 | G4double MigdalFactor = (material->GetElectronDensity())*MigdalConstant |
---|
718 | / (epsilmax*epsilmax); |
---|
719 | |
---|
720 | G4double x, epsil, greject, migdal, grejmax, q; |
---|
721 | G4double U = log(kineticEnergy/electron_mass_c2); |
---|
722 | G4double U2 = U*U; |
---|
723 | |
---|
724 | // precalculated parameters |
---|
725 | G4double ah, bh; |
---|
726 | G4double screenfac = 0.0; |
---|
727 | |
---|
728 | if (kineticEnergy > tlow) { |
---|
729 | |
---|
730 | G4double ah1 = ah10 + ZZ* (ah11 + ZZ* ah12); |
---|
731 | G4double ah2 = ah20 + ZZ* (ah21 + ZZ* ah22); |
---|
732 | G4double ah3 = ah30 + ZZ* (ah31 + ZZ* ah32); |
---|
733 | |
---|
734 | G4double bh1 = bh10 + ZZ* (bh11 + ZZ* bh12); |
---|
735 | G4double bh2 = bh20 + ZZ* (bh21 + ZZ* bh22); |
---|
736 | G4double bh3 = bh30 + ZZ* (bh31 + ZZ* bh32); |
---|
737 | |
---|
738 | ah = 1. + (ah1*U2 + ah2*U + ah3) / (U2*U); |
---|
739 | bh = 0.75 + (bh1*U2 + bh2*U + bh3) / (U2*U); |
---|
740 | |
---|
741 | // limit of the screening variable |
---|
742 | screenfac = |
---|
743 | 136.*electron_mass_c2/((anElement->GetIonisation()->GetZ3())*totalEnergy); |
---|
744 | G4double screenmin = screenfac*epsilmin/(1.-epsilmin); |
---|
745 | |
---|
746 | // Compute the maximum of the rejection function |
---|
747 | G4double F1 = max(ScreenFunction1(screenmin) - FZ ,0.); |
---|
748 | G4double F2 = max(ScreenFunction2(screenmin) - FZ ,0.); |
---|
749 | grejmax = (F1 - epsilmin* (F1*ah - bh*epsilmin*F2))/(42.392 - FZ); |
---|
750 | |
---|
751 | } else { |
---|
752 | |
---|
753 | G4double al0 = al00 + ZZ* (al01 + ZZ* al02); |
---|
754 | G4double al1 = al10 + ZZ* (al11 + ZZ* al12); |
---|
755 | G4double al2 = al20 + ZZ* (al21 + ZZ* al22); |
---|
756 | |
---|
757 | G4double bl0 = bl00 + ZZ* (bl01 + ZZ* bl02); |
---|
758 | G4double bl1 = bl10 + ZZ* (bl11 + ZZ* bl12); |
---|
759 | G4double bl2 = bl20 + ZZ* (bl21 + ZZ* bl22); |
---|
760 | |
---|
761 | ah = al0 + al1*U + al2*U2; |
---|
762 | bh = bl0 + bl1*U + bl2*U2; |
---|
763 | |
---|
764 | // Compute the maximum of the rejection function |
---|
765 | grejmax = max(1. + xmin* (ah + bh*xmin), 1.+ah+bh); |
---|
766 | G4double xm = -ah/(2.*bh); |
---|
767 | if ( xmin < xm && xm < xmax) grejmax = max(grejmax, 1.+ xm* (ah + bh*xm)); |
---|
768 | } |
---|
769 | |
---|
770 | // |
---|
771 | // sample the energy rate of the emitted gamma for e- kin energy > 1 MeV |
---|
772 | // |
---|
773 | |
---|
774 | do { |
---|
775 | if (kineticEnergy > tlow) { |
---|
776 | do { |
---|
777 | q = G4UniformRand(); |
---|
778 | x = pow(xmin, q + kappa*(1.0 - q)); |
---|
779 | epsil = x*kineticEnergy/totalEnergy; |
---|
780 | G4double screenvar = screenfac*epsil/(1.0-epsil); |
---|
781 | G4double F1 = max(ScreenFunction1(screenvar) - FZ ,0.); |
---|
782 | G4double F2 = max(ScreenFunction2(screenvar) - FZ ,0.); |
---|
783 | migdal = (1. + MigdalFactor)/(1. + MigdalFactor/(x*x)); |
---|
784 | greject = migdal*(F1 - epsil* (ah*F1 - bh*epsil*F2))/(42.392 - FZ); |
---|
785 | /* |
---|
786 | if ( greject > grejmax ) { |
---|
787 | G4cout << "### G4eBremsstrahlungModel Warning: Majoranta exceeded! " |
---|
788 | << greject << " > " << grejmax |
---|
789 | << " x= " << x |
---|
790 | << " e= " << kineticEnergy |
---|
791 | << G4endl; |
---|
792 | } |
---|
793 | */ |
---|
794 | } while( greject < G4UniformRand()*grejmax ); |
---|
795 | |
---|
796 | } else { |
---|
797 | |
---|
798 | do { |
---|
799 | q = G4UniformRand(); |
---|
800 | x = pow(xmin, q + kappa*(1.0 - q)); |
---|
801 | migdal = (1. + MigdalFactor)/(1. + MigdalFactor/(x*x)); |
---|
802 | greject = migdal*(1. + x* (ah + bh*x)); |
---|
803 | /* |
---|
804 | if ( greject > grejmax ) { |
---|
805 | G4cout << "### G4eBremsstrahlungModel Warning: Majoranta exceeded! " |
---|
806 | << greject << " > " << grejmax |
---|
807 | << " x= " << x |
---|
808 | << " e= " << kineticEnergy |
---|
809 | << G4endl; |
---|
810 | } |
---|
811 | */ |
---|
812 | } while( greject < G4UniformRand()*grejmax ); |
---|
813 | } |
---|
814 | /* |
---|
815 | if(x > 0.999) { |
---|
816 | G4cout << "### G4eBremsstrahlungModel Warning: e= " << kineticEnergy |
---|
817 | << " tlow= " << tlow |
---|
818 | << " x= " << x |
---|
819 | << " greject= " << greject |
---|
820 | << " grejmax= " << grejmax |
---|
821 | << " migdal= " << migdal |
---|
822 | << G4endl; |
---|
823 | // if(x >= 1.0) G4Exception("X=1"); |
---|
824 | } |
---|
825 | */ |
---|
826 | gammaEnergy = x*kineticEnergy; |
---|
827 | |
---|
828 | if (LPMFlag()) { |
---|
829 | // take into account the supression due to the LPM effect |
---|
830 | if (G4UniformRand() <= SupressionFunction(material,kineticEnergy, |
---|
831 | gammaEnergy)) |
---|
832 | LPMOK = true; |
---|
833 | } |
---|
834 | else LPMOK = true; |
---|
835 | |
---|
836 | } while (!LPMOK); |
---|
837 | |
---|
838 | // |
---|
839 | // angles of the emitted gamma. ( Z - axis along the parent particle) |
---|
840 | // |
---|
841 | // universal distribution suggested by L. Urban |
---|
842 | // (Geant3 manual (1993) Phys211), |
---|
843 | // derived from Tsai distribution (Rev Mod Phys 49,421(1977)) |
---|
844 | |
---|
845 | G4double u; |
---|
846 | const G4double a1 = 0.625 , a2 = 3.*a1 , d = 27. ; |
---|
847 | |
---|
848 | if (9./(9.+d) > G4UniformRand()) u = - log(G4UniformRand()*G4UniformRand())/a1; |
---|
849 | else u = - log(G4UniformRand()*G4UniformRand())/a2; |
---|
850 | |
---|
851 | G4double theta = u*electron_mass_c2/totalEnergy; |
---|
852 | |
---|
853 | G4double sint = sin(theta); |
---|
854 | |
---|
855 | G4double phi = twopi * G4UniformRand() ; |
---|
856 | |
---|
857 | G4ThreeVector gammaDirection(sint*cos(phi),sint*sin(phi), cos(theta)); |
---|
858 | gammaDirection.rotateUz(direction); |
---|
859 | |
---|
860 | // create G4DynamicParticle object for the Gamma |
---|
861 | G4DynamicParticle* g = new G4DynamicParticle(theGamma,gammaDirection, |
---|
862 | gammaEnergy); |
---|
863 | vdp->push_back(g); |
---|
864 | |
---|
865 | G4double totMomentum = sqrt(kineticEnergy*(totalEnergy + electron_mass_c2)); |
---|
866 | G4ThreeVector dir = totMomentum*direction - gammaEnergy*gammaDirection; |
---|
867 | direction = dir.unit(); |
---|
868 | |
---|
869 | // energy of primary |
---|
870 | G4double finalE = kineticEnergy - gammaEnergy; |
---|
871 | |
---|
872 | // stop tracking and create new secondary instead of primary |
---|
873 | if(gammaEnergy > SecondaryThreshold()) { |
---|
874 | fParticleChange->ProposeTrackStatus(fStopAndKill); |
---|
875 | fParticleChange->SetProposedKineticEnergy(0.0); |
---|
876 | G4DynamicParticle* el = |
---|
877 | new G4DynamicParticle(const_cast<G4ParticleDefinition*>(particle), |
---|
878 | direction, finalE); |
---|
879 | vdp->push_back(el); |
---|
880 | |
---|
881 | // continue tracking |
---|
882 | } else { |
---|
883 | fParticleChange->SetProposedMomentumDirection(direction); |
---|
884 | fParticleChange->SetProposedKineticEnergy(finalE); |
---|
885 | } |
---|
886 | } |
---|
887 | |
---|
888 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
---|
889 | |
---|
890 | const G4Element* G4eBremsstrahlungModel::SelectRandomAtom( |
---|
891 | const G4MaterialCutsCouple* couple) |
---|
892 | { |
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893 | // select randomly 1 element within the material |
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894 | |
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895 | const G4Material* material = couple->GetMaterial(); |
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896 | G4int nElements = material->GetNumberOfElements(); |
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897 | const G4ElementVector* theElementVector = material->GetElementVector(); |
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898 | |
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899 | const G4Element* elm = 0; |
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900 | |
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901 | if(1 < nElements) { |
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902 | |
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903 | G4DataVector* dv = partialSumSigma[couple->GetIndex()]; |
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904 | G4double rval = G4UniformRand()*((*dv)[nElements-1]); |
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905 | |
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906 | for (G4int i=0; i<nElements; i++) { |
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907 | if (rval <= (*dv)[i]) elm = (*theElementVector)[i]; |
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908 | } |
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909 | if(!elm) { |
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910 | G4cout << "G4eBremsstrahlungModel::SelectRandomAtom: Warning -" |
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911 | << " no elements found in " |
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912 | << material->GetName() |
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913 | << G4endl; |
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914 | elm = (*theElementVector)[0]; |
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915 | } |
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916 | } else elm = (*theElementVector)[0]; |
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917 | |
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918 | SetCurrentElement(elm); |
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919 | return elm; |
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920 | } |
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921 | |
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922 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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923 | |
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924 | G4double G4eBremsstrahlungModel::SupressionFunction(const G4Material* material, |
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925 | G4double kineticEnergy, G4double gammaEnergy) |
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926 | { |
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927 | // supression due to the LPM effect+polarisation of the medium/ |
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928 | // supression due to the polarisation alone |
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929 | |
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930 | |
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931 | G4double totEnergy = kineticEnergy+electron_mass_c2 ; |
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932 | G4double totEnergySquare = totEnergy*totEnergy ; |
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933 | |
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934 | G4double LPMEnergy = LPMconstant*(material->GetRadlen()) ; |
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935 | |
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936 | G4double gammaEnergySquare = gammaEnergy*gammaEnergy ; |
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937 | |
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938 | G4double electronDensity = material->GetElectronDensity(); |
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939 | |
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940 | G4double sp = gammaEnergySquare/ |
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941 | (gammaEnergySquare+MigdalConstant*totEnergySquare*electronDensity); |
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942 | |
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943 | G4double supr = 1.0; |
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944 | |
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945 | if (LPMFlag()) { |
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946 | |
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947 | G4double s2lpm = LPMEnergy*gammaEnergy/totEnergySquare; |
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948 | |
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949 | if (s2lpm < 1.) { |
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950 | |
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951 | G4double LPMgEnergyLimit = totEnergySquare/LPMEnergy ; |
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952 | G4double LPMgEnergyLimit2 = LPMgEnergyLimit*LPMgEnergyLimit; |
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953 | G4double splim = LPMgEnergyLimit2/ |
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954 | (LPMgEnergyLimit2+MigdalConstant*totEnergySquare*electronDensity); |
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955 | G4double w = 1.+1./splim ; |
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956 | |
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957 | if ((1.-sp) < 1.e-6) w = s2lpm*(3.-sp); |
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958 | else w = s2lpm*(1.+1./sp); |
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959 | |
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960 | supr = (sqrt(w*w+4.*s2lpm)-w)/(sqrt(w*w+4.)-w) ; |
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961 | supr /= sp; |
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962 | } |
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963 | |
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964 | } |
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965 | return supr; |
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966 | } |
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967 | |
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968 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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969 | |
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970 | |
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