1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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13 | // * work make any representation or warranty, express or implied, * |
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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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16 | // * for the full disclaimer and the limitation of liability. * |
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17 | // * * |
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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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20 | // * By using, copying, modifying or distributing the software (or * |
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22 | // * use in resulting scientific publications, and indicate your * |
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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: G4KleinNishinaModel.cc,v 1.1 2010/09/03 14:11:16 vnivanch Exp $ |
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27 | // GEANT4 tag $Name: emstand-V09-03-24 $ |
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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: G4KleinNishinaModel |
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35 | // |
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36 | // Author: Vladimir Ivanchenko on base of G4KleinNishinaCompton |
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37 | // |
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38 | // Creation date: 13.06.2010 |
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39 | // |
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40 | // Modifications: |
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41 | // |
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42 | // Class Description: |
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43 | // |
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44 | // ------------------------------------------------------------------- |
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45 | // |
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46 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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47 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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48 | |
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49 | #include "G4KleinNishinaModel.hh" |
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50 | #include "G4Electron.hh" |
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51 | #include "G4Gamma.hh" |
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52 | #include "Randomize.hh" |
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53 | #include "G4RandomDirection.hh" |
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54 | #include "G4DataVector.hh" |
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55 | #include "G4ParticleChangeForGamma.hh" |
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56 | #include "G4VAtomDeexcitation.hh" |
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57 | #include "G4LossTableManager.hh" |
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58 | |
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59 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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60 | |
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61 | using namespace std; |
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62 | |
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63 | G4KleinNishinaModel::G4KleinNishinaModel(const G4String& nam) |
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64 | : G4VEmModel(nam),isInitialized(false) |
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65 | { |
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66 | theGamma = G4Gamma::Gamma(); |
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67 | theElectron = G4Electron::Electron(); |
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68 | lowestGammaEnergy = 1.0*eV; |
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69 | fProbabilities.resize(9,0.0); |
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70 | } |
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71 | |
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72 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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73 | |
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74 | G4KleinNishinaModel::~G4KleinNishinaModel() |
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75 | {} |
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76 | |
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77 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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78 | |
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79 | void G4KleinNishinaModel::Initialise(const G4ParticleDefinition* p, |
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80 | const G4DataVector& cuts) |
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81 | { |
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82 | fAtomDeexcitation = G4LossTableManager::Instance()->AtomDeexcitation(); |
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83 | InitialiseElementSelectors(p, cuts); |
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84 | |
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85 | if (isInitialized) { return; } |
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86 | fParticleChange = GetParticleChangeForGamma(); |
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87 | isInitialized = true; |
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88 | } |
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89 | |
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90 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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91 | |
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92 | G4double |
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93 | G4KleinNishinaModel::ComputeCrossSectionPerAtom(const G4ParticleDefinition*, |
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94 | G4double GammaEnergy, |
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95 | G4double Z, G4double, |
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96 | G4double, G4double) |
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97 | { |
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98 | G4double CrossSection = 0.0 ; |
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99 | if ( Z < 0.9999 || GammaEnergy < 0.1*keV) { return CrossSection; } |
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100 | |
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101 | static const G4double a = 20.0 , b = 230.0 , c = 440.0; |
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102 | |
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103 | static const G4double |
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104 | d1= 2.7965e-1*barn, d2=-1.8300e-1*barn, d3= 6.7527 *barn, d4=-1.9798e+1*barn, |
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105 | e1= 1.9756e-5*barn, e2=-1.0205e-2*barn, e3=-7.3913e-2*barn, e4= 2.7079e-2*barn, |
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106 | f1=-3.9178e-7*barn, f2= 6.8241e-5*barn, f3= 6.0480e-5*barn, f4= 3.0274e-4*barn; |
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107 | |
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108 | G4double p1Z = Z*(d1 + e1*Z + f1*Z*Z), p2Z = Z*(d2 + e2*Z + f2*Z*Z), |
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109 | p3Z = Z*(d3 + e3*Z + f3*Z*Z), p4Z = Z*(d4 + e4*Z + f4*Z*Z); |
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110 | |
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111 | G4double T0 = 15.0*keV; |
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112 | if (Z < 1.5) { T0 = 40.0*keV; } |
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113 | |
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114 | G4double X = max(GammaEnergy, T0) / electron_mass_c2; |
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115 | CrossSection = p1Z*std::log(1.+2.*X)/X |
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116 | + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X); |
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117 | |
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118 | // modification for low energy. (special case for Hydrogen) |
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119 | if (GammaEnergy < T0) { |
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120 | G4double dT0 = keV; |
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121 | X = (T0+dT0) / electron_mass_c2 ; |
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122 | G4double sigma = p1Z*log(1.+2*X)/X |
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123 | + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X); |
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124 | G4double c1 = -T0*(sigma-CrossSection)/(CrossSection*dT0); |
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125 | G4double c2 = 0.150; |
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126 | if (Z > 1.5) { c2 = 0.375-0.0556*log(Z); } |
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127 | G4double y = log(GammaEnergy/T0); |
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128 | CrossSection *= exp(-y*(c1+c2*y)); |
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129 | } |
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130 | // G4cout << "e= " << GammaEnergy << " Z= " << Z |
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131 | // << " cross= " << CrossSection << G4endl; |
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132 | return CrossSection; |
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133 | } |
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134 | |
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135 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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136 | |
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137 | void G4KleinNishinaModel::SampleSecondaries( |
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138 | std::vector<G4DynamicParticle*>* fvect, |
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139 | const G4MaterialCutsCouple* couple, |
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140 | const G4DynamicParticle* aDynamicGamma, |
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141 | G4double, |
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142 | G4double) |
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143 | { |
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144 | G4double energy = aDynamicGamma->GetKineticEnergy(); |
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145 | G4ThreeVector direction = aDynamicGamma->GetMomentumDirection(); |
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146 | |
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147 | // select atom |
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148 | const G4Element* elm = SelectRandomAtom(couple, theGamma, energy); |
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149 | |
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150 | // select shell first |
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151 | G4int Z = (G4int)elm->GetZ(); |
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152 | G4int nShells = elm->GetNbOfAtomicShells(); |
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153 | if(nShells > (G4int)fProbabilities.size()) { fProbabilities.resize(nShells); } |
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154 | G4double totprob = 0.0; |
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155 | G4int i = 0; |
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156 | for(; i<nShells; ++i) { |
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157 | G4double prob = 0.0; |
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158 | if(energy > elm->GetAtomicShell(i)) { |
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159 | prob = (G4double)elm->GetNbOfShellElectrons(i); |
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160 | } |
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161 | totprob += prob; |
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162 | fProbabilities[i] = totprob; |
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163 | } |
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164 | if(totprob == 0.0) { return; } |
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165 | |
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166 | G4LorentzVector lv1, lv2, lv3; |
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167 | G4LorentzVector lv0(energy*direction.x(),energy*direction.y(), |
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168 | energy*direction.z(),energy); |
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169 | G4double eKinEnergy = 0.0; |
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170 | G4double gamEnergy1 = 0.0; |
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171 | |
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172 | // Loop on sampling |
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173 | do { |
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174 | G4double xprob = totprob*G4UniformRand(); |
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175 | |
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176 | for(i=0; i<nShells; ++i) { if(xprob <= fProbabilities[i]) {break;} } |
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177 | if( i == nShells ) { return; } |
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178 | |
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179 | G4double bindingEnergy = elm->GetAtomicShell(i); |
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180 | G4double tkin = bindingEnergy*0.5; |
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181 | G4double eEnergy = tkin + electron_mass_c2; |
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182 | G4double eTotMomentum = sqrt(tkin*(tkin + electron_mass_c2*2)); |
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183 | G4ThreeVector eDir = G4RandomDirection(); |
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184 | lv1 = lv0; |
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185 | lv2.set(eTotMomentum*eDir.x(),eTotMomentum*eDir.y(), |
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186 | eTotMomentum*eDir.z(),eEnergy); |
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187 | G4ThreeVector bst = lv2.boostVector(); |
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188 | lv1.boost(-bst); |
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189 | |
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190 | // In the rest frame of an electron |
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191 | // The scattered gamma energy is sampled according to Klein - Nishina formula. |
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192 | // The random number techniques of Butcher & Messel are used |
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193 | // (Nuc Phys 20(1960),15). |
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194 | |
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195 | G4double gamEnergy0 = lv1.e(); |
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196 | G4double E0_m = gamEnergy0 / electron_mass_c2 ; |
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197 | |
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198 | G4ThreeVector gamDirection0 = (lv1.vect()).unit(); |
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199 | |
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200 | // |
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201 | // sample the energy rate of the scattered gamma |
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202 | // |
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203 | |
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204 | G4double epsilon, epsilonsq, onecost, sint2, greject ; |
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205 | |
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206 | G4double epsilon0 = 1./(1. + 2.*E0_m); |
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207 | G4double epsilon0sq = epsilon0*epsilon0; |
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208 | G4double alpha1 = - log(epsilon0); |
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209 | G4double alpha2 = 0.5*(1.- epsilon0sq); |
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210 | |
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211 | do { |
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212 | if ( alpha1/(alpha1+alpha2) > G4UniformRand() ) { |
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213 | epsilon = exp(-alpha1*G4UniformRand()); // epsilon0**r |
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214 | epsilonsq = epsilon*epsilon; |
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215 | |
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216 | } else { |
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217 | epsilonsq = epsilon0sq + (1.- epsilon0sq)*G4UniformRand(); |
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218 | epsilon = sqrt(epsilonsq); |
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219 | }; |
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220 | |
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221 | onecost = (1.- epsilon)/(epsilon*E0_m); |
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222 | sint2 = onecost*(2.-onecost); |
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223 | greject = 1. - epsilon*sint2/(1.+ epsilonsq); |
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224 | |
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225 | } while (greject < G4UniformRand()); |
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226 | |
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227 | // |
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228 | // scattered gamma angles. ( Z - axis along the parent gamma) |
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229 | // |
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230 | |
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231 | G4double cosTeta = 1. - onecost; |
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232 | G4double sinTeta = sqrt (sint2); |
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233 | G4double Phi = twopi * G4UniformRand(); |
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234 | G4double dirx = sinTeta*cos(Phi), diry = sinTeta*sin(Phi), dirz = cosTeta; |
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235 | |
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236 | // |
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237 | // update G4VParticleChange for the scattered gamma |
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238 | // |
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239 | |
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240 | G4ThreeVector gamDirection1 ( dirx,diry,dirz ); |
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241 | gamDirection1.rotateUz(gamDirection0); |
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242 | gamEnergy1 = epsilon*gamEnergy0; |
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243 | |
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244 | // before scattering |
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245 | lv2.set(0.0,0.0,0.0,electron_mass_c2); |
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246 | lv2 += lv1; |
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247 | |
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248 | // after scattering |
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249 | lv1.set(gamEnergy1*gamDirection1.x(),gamEnergy1*gamDirection1.y(), |
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250 | gamEnergy1*gamDirection1.z(),gamEnergy1); |
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251 | lv2 -= lv1; |
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252 | lv2.boost(bst); |
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253 | lv1.boost(bst); |
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254 | eKinEnergy = lv2.e() - electron_mass_c2 - bindingEnergy; |
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255 | } while ( eKinEnergy < 0.0 ); |
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256 | |
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257 | // gamma kinematics |
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258 | gamEnergy1 = lv1.e(); |
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259 | if(gamEnergy1 > lowestGammaEnergy) { |
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260 | fParticleChange->SetProposedKineticEnergy(gamEnergy1); |
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261 | fParticleChange->ProposeMomentumDirection((lv1.vect()).unit()); |
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262 | } else { |
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263 | fParticleChange->ProposeTrackStatus(fStopAndKill); |
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264 | fParticleChange->ProposeLocalEnergyDeposit(gamEnergy1); |
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265 | } |
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266 | |
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267 | // |
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268 | // kinematic of the scattered electron |
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269 | // |
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270 | if(eKinEnergy > DBL_MIN) { |
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271 | G4ThreeVector eDirection = (lv2.vect()).unit(); |
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272 | G4DynamicParticle* dp = new G4DynamicParticle(theElectron,eDirection,eKinEnergy); |
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273 | fvect->push_back(dp); |
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274 | } |
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275 | // sample deexcitation |
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276 | // |
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277 | if(fAtomDeexcitation) { |
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278 | G4AtomicShellEnumerator as = G4AtomicShellEnumerator(i); |
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279 | const G4AtomicShell* shell = fAtomDeexcitation->GetAtomicShell(Z, as); |
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280 | fAtomDeexcitation->GenerateParticles(fvect, shell, Z, couple->GetIndex()); |
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281 | } |
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282 | } |
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283 | |
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284 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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285 | |
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