1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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9 | // * include a list of copyright holders. * |
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11 | // * Neither the authors of this software system, nor their employing * |
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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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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: G4eCoulombScatteringModel.cc,v 1.69 2009/05/10 16:09:29 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: G4eCoulombScatteringModel |
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35 | // |
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36 | // Author: Vladimir Ivanchenko |
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37 | // |
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38 | // Creation date: 22.08.2005 |
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39 | // |
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40 | // Modifications: |
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41 | // 01.08.06 V.Ivanchenko extend upper limit of table to TeV and review the |
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42 | // logic of building - only elements from G4ElementTable |
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43 | // 08.08.06 V.Ivanchenko build internal table in ekin scale, introduce faclim |
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44 | // 19.08.06 V.Ivanchenko add inline function ScreeningParameter |
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45 | // 09.10.07 V.Ivanchenko reorganized methods, add cut dependence in scattering off e- |
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46 | // 09.06.08 V.Ivanchenko add SelectIsotope and sampling of the recoil ion |
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47 | // |
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48 | // Class Description: |
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49 | // |
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50 | // ------------------------------------------------------------------- |
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51 | // |
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52 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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53 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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54 | |
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55 | #include "G4eCoulombScatteringModel.hh" |
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56 | #include "Randomize.hh" |
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57 | #include "G4DataVector.hh" |
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58 | #include "G4ElementTable.hh" |
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59 | #include "G4PhysicsLogVector.hh" |
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60 | #include "G4ParticleChangeForGamma.hh" |
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61 | #include "G4Electron.hh" |
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62 | #include "G4Positron.hh" |
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63 | #include "G4Proton.hh" |
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64 | #include "G4ParticleTable.hh" |
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65 | |
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66 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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67 | |
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68 | G4double G4eCoulombScatteringModel::ScreenRSquare[] = {0.0}; |
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69 | G4double G4eCoulombScatteringModel::FormFactor[] = {0.0}; |
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70 | |
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71 | using namespace std; |
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72 | |
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73 | G4eCoulombScatteringModel::G4eCoulombScatteringModel(const G4String& nam) |
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74 | : G4VEmModel(nam), |
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75 | cosThetaMin(1.0), |
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76 | cosThetaMax(-1.0), |
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77 | q2Limit(TeV*TeV), |
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78 | alpha2(fine_structure_const*fine_structure_const), |
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79 | faclim(100.0), |
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80 | isInitialised(false) |
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81 | { |
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82 | fNistManager = G4NistManager::Instance(); |
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83 | theParticleTable = G4ParticleTable::GetParticleTable(); |
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84 | theElectron = G4Electron::Electron(); |
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85 | thePositron = G4Positron::Positron(); |
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86 | theProton = G4Proton::Proton(); |
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87 | currentMaterial = 0; |
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88 | currentElement = 0; |
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89 | lowEnergyLimit = keV; |
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90 | G4double p0 = electron_mass_c2*classic_electr_radius; |
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91 | coeff = twopi*p0*p0; |
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92 | tkin = targetZ = mom2 = DBL_MIN; |
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93 | elecXSection = nucXSection = 0.0; |
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94 | recoilThreshold = 100.*keV; |
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95 | ecut = DBL_MAX; |
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96 | particle = 0; |
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97 | currentCouple = 0; |
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98 | |
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99 | // Thomas-Fermi screening radii |
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100 | // Formfactors from A.V. Butkevich et al., NIM A 488 (2002) 282 |
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101 | |
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102 | if(0.0 == ScreenRSquare[0]) { |
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103 | G4double a0 = electron_mass_c2/0.88534; |
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104 | G4double constn = 6.937e-6/(MeV*MeV); |
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105 | |
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106 | ScreenRSquare[0] = alpha2*a0*a0; |
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107 | for(G4int j=1; j<100; j++) { |
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108 | G4double x = a0*fNistManager->GetZ13(j); |
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109 | ScreenRSquare[j] = alpha2*x*x; |
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110 | x = fNistManager->GetA27(j); |
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111 | FormFactor[j] = constn*x*x; |
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112 | } |
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113 | } |
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114 | } |
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115 | |
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116 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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117 | |
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118 | G4eCoulombScatteringModel::~G4eCoulombScatteringModel() |
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119 | {} |
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120 | |
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121 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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122 | |
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123 | void G4eCoulombScatteringModel::Initialise(const G4ParticleDefinition* p, |
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124 | const G4DataVector& cuts) |
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125 | { |
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126 | SetupParticle(p); |
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127 | currentCouple = 0; |
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128 | elecXSection = nucXSection = 0.0; |
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129 | tkin = targetZ = mom2 = DBL_MIN; |
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130 | ecut = etag = DBL_MAX; |
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131 | cosThetaMin = cos(PolarAngleLimit()); |
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132 | currentCuts = &cuts; |
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133 | //G4cout << "!!! G4eCoulombScatteringModel::Initialise for " |
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134 | // << p->GetParticleName() << " cos(TetMin)= " << cosThetaMin |
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135 | // << " cos(TetMax)= " << cosThetaMax <<G4endl; |
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136 | if(!isInitialised) { |
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137 | isInitialised = true; |
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138 | fParticleChange = GetParticleChangeForGamma(); |
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139 | } |
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140 | if(mass < GeV && particle->GetParticleType() != "nucleus") { |
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141 | InitialiseElementSelectors(p,cuts); |
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142 | } |
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143 | } |
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144 | |
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145 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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146 | |
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147 | void G4eCoulombScatteringModel::ComputeMaxElectronScattering(G4double cutEnergy) |
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148 | { |
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149 | ecut = cutEnergy; |
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150 | G4double tmax = tkin; |
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151 | cosTetMaxElec = 1.0; |
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152 | if(mass > MeV) { |
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153 | G4double ratio = electron_mass_c2/mass; |
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154 | G4double tau = tkin/mass; |
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155 | tmax = 2.0*electron_mass_c2*tau*(tau + 2.)/ |
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156 | (1.0 + 2.0*ratio*(tau + 1.0) + ratio*ratio); |
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157 | cosTetMaxElec = 1.0 - std::min(cutEnergy, tmax)*electron_mass_c2/mom2; |
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158 | } else { |
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159 | |
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160 | if(particle == theElectron) tmax *= 0.5; |
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161 | G4double t = std::min(cutEnergy, tmax); |
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162 | G4double mom21 = t*(t + 2.0*electron_mass_c2); |
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163 | G4double t1 = tkin - t; |
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164 | //G4cout << "tkin= " << tkin << " t= " << t << " t1= " << t1 << G4endl; |
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165 | if(t1 > 0.0) { |
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166 | G4double mom22 = t1*(t1 + 2.0*mass); |
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167 | G4double ctm = (mom2 + mom22 - mom21)*0.5/sqrt(mom2*mom22); |
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168 | //G4cout << "ctm= " << ctm << G4endl; |
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169 | if(ctm < 1.0) cosTetMaxElec = ctm; |
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170 | if(ctm < -1.0) cosTetMaxElec = -1.0; |
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171 | } |
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172 | } |
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173 | } |
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174 | |
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175 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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176 | |
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177 | G4double G4eCoulombScatteringModel::ComputeCrossSectionPerAtom( |
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178 | const G4ParticleDefinition* p, |
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179 | G4double kinEnergy, |
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180 | G4double Z, G4double, |
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181 | G4double cutEnergy, G4double) |
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182 | { |
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183 | //G4cout << "### G4eCoulombScatteringModel::ComputeCrossSectionPerAtom for " |
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184 | // << p->GetParticleName()<<" Z= "<<Z<<" e(MeV)= "<< kinEnergy/MeV << G4endl; |
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185 | G4double xsec = 0.0; |
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186 | SetupParticle(p); |
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187 | G4double ekin = std::max(lowEnergyLimit, kinEnergy); |
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188 | SetupKinematic(ekin, cutEnergy); |
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189 | if(cosTetMaxNuc < cosTetMinNuc) { |
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190 | SetupTarget(Z, ekin); |
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191 | xsec = CrossSectionPerAtom(); |
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192 | } |
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193 | /* |
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194 | G4cout << "e(MeV)= " << ekin/MeV << "cosTetMinNuc= " << cosTetMinNuc |
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195 | << " cosTetMaxNuc= " << cosTetMaxNuc |
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196 | << " cosTetMaxElec= " << cosTetMaxElec |
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197 | << " screenZ= " << screenZ |
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198 | << " formfactA= " << formfactA |
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199 | << " cosTetMaxHad= " << cosTetMaxHad << G4endl; |
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200 | */ |
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201 | return xsec; |
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202 | } |
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203 | |
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204 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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205 | |
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206 | G4double G4eCoulombScatteringModel::CrossSectionPerAtom() |
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207 | { |
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208 | // This method needs initialisation before be called |
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209 | G4double fac = coeff*targetZ*chargeSquare*kinFactor; |
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210 | elecXSection = 0.0; |
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211 | nucXSection = 0.0; |
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212 | |
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213 | G4double x = 1.0 - cosTetMinNuc; |
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214 | G4double x1 = x + screenZ; |
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215 | |
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216 | if(cosTetMaxElec2 < cosTetMinNuc) { |
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217 | elecXSection = fac*(cosTetMinNuc - cosTetMaxElec2)/ |
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218 | (x1*(1.0 - cosTetMaxElec2 + screenZ)); |
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219 | nucXSection = elecXSection; |
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220 | } |
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221 | |
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222 | //G4cout << "XS tkin(MeV)= " << tkin<<" xs= " <<nucXSection |
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223 | // << " costmax= " << cosTetMaxNuc2 |
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224 | // << " costmin= " << cosTetMinNuc << " Z= " << targetZ <<G4endl; |
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225 | if(cosTetMaxNuc2 < cosTetMinNuc) { |
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226 | G4double s = screenZ*formfactA; |
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227 | G4double z1 = 1.0 - cosTetMaxNuc2 + screenZ; |
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228 | G4double s1 = 1.0 - s; |
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229 | G4double d = s1/formfactA; |
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230 | //G4cout <<"x1= "<<x1<<" z1= " <<z1<<" s= "<<s << " d= " <<d <<G4endl; |
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231 | if(d < 0.2*x1) { |
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232 | G4double x2 = x1*x1; |
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233 | G4double z2 = z1*z1; |
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234 | x = (1.0/(x1*x2) - 1.0/(z1*z2) - d*1.5*(1.0/(x2*x2) - 1.0/(z2*z2)))/ |
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235 | (3.0*formfactA*formfactA); |
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236 | } else { |
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237 | G4double x2 = x1 + d; |
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238 | G4double z2 = z1 + d; |
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239 | x = (1.0/x1 - 1.0/z1 + 1.0/x2 - 1.0/z2 - 2.0*log(z1*x2/(z2*x1))/d)/(s1*s1); |
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240 | } |
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241 | nucXSection += fac*targetZ*x; |
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242 | } |
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243 | //G4cout<<" cross(bn)= "<<nucXSection/barn<<" xsElec(bn)= "<<elecXSection/barn |
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244 | // << " Asc= " << screenZ << G4endl; |
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245 | |
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246 | return nucXSection; |
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247 | } |
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248 | |
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249 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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250 | |
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251 | void G4eCoulombScatteringModel::SampleSecondaries( |
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252 | std::vector<G4DynamicParticle*>* fvect, |
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253 | const G4MaterialCutsCouple* couple, |
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254 | const G4DynamicParticle* dp, |
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255 | G4double cutEnergy, |
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256 | G4double) |
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257 | { |
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258 | G4double kinEnergy = dp->GetKineticEnergy(); |
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259 | if(kinEnergy <= DBL_MIN) return; |
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260 | DefineMaterial(couple); |
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261 | SetupParticle(dp->GetDefinition()); |
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262 | G4double ekin = std::max(lowEnergyLimit, kinEnergy); |
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263 | SetupKinematic(ekin, cutEnergy); |
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264 | //G4cout << "G4eCoulombScatteringModel::SampleSecondaries e(MeV)= " |
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265 | // << kinEnergy << " " << particle->GetParticleName() << G4endl; |
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266 | |
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267 | // Choose nucleus |
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268 | currentElement = SelectRandomAtom(couple,particle,ekin,cutEnergy,ekin); |
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269 | |
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270 | SetupTarget(currentElement->GetZ(),ekin); |
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271 | |
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272 | G4double cost = SampleCosineTheta(); |
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273 | G4double z1 = 1.0 - cost; |
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274 | if(z1 < 0.0) return; |
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275 | |
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276 | G4double sint = sqrt(z1*(1.0 + cost)); |
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277 | |
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278 | //G4cout<<"## Sampled sint= " << sint << " Z= " << targetZ |
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279 | // << " screenZ= " << screenZ << " cn= " << formfactA << G4endl; |
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280 | |
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281 | G4double phi = twopi * G4UniformRand(); |
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282 | |
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283 | G4ThreeVector direction = dp->GetMomentumDirection(); |
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284 | G4ThreeVector newDirection(cos(phi)*sint,sin(phi)*sint,cost); |
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285 | newDirection.rotateUz(direction); |
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286 | |
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287 | fParticleChange->ProposeMomentumDirection(newDirection); |
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288 | |
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289 | // recoil sampling assuming a small recoil |
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290 | // and first order correction to primary 4-momentum |
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291 | if(lowEnergyLimit < kinEnergy) { |
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292 | G4int ia = SelectIsotopeNumber(currentElement); |
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293 | G4double Trec = z1*mom2/(amu_c2*G4double(ia)); |
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294 | |
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295 | if(Trec > recoilThreshold) { |
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296 | G4ParticleDefinition* ion = theParticleTable->FindIon(iz, ia, 0, iz); |
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297 | Trec = z1*mom2/ion->GetPDGMass(); |
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298 | if(Trec < kinEnergy) { |
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299 | G4ThreeVector dir = (direction - newDirection).unit(); |
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300 | G4DynamicParticle* newdp = new G4DynamicParticle(ion, dir, Trec); |
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301 | fvect->push_back(newdp); |
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302 | fParticleChange->SetProposedKineticEnergy(kinEnergy - Trec); |
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303 | } |
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304 | } |
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305 | } |
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306 | |
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307 | return; |
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308 | } |
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309 | |
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310 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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311 | |
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312 | G4double G4eCoulombScatteringModel::SampleCosineTheta() |
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313 | { |
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314 | G4double costm = cosTetMaxNuc2; |
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315 | G4double formf = formfactA; |
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316 | G4double prob = 0.0; |
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317 | G4double xs = CrossSectionPerAtom(); |
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318 | if(xs > 0.0) prob = elecXSection/xs; |
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319 | |
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320 | // scattering off e or A? |
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321 | if(G4UniformRand() < prob) { |
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322 | costm = cosTetMaxElec2; |
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323 | formf = 0.0; |
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324 | } |
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325 | |
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326 | /* |
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327 | G4cout << "SampleCost: e(MeV)= " << tkin |
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328 | << " ctmin= " << cosThetaMin |
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329 | << " ctmaxN= " << cosTetMaxNuc |
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330 | << " ctmax= " << costm |
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331 | << " Z= " << targetZ << " A= " << targetA |
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332 | << G4endl; |
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333 | */ |
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334 | if(costm >= cosTetMinNuc) return 2.0; |
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335 | |
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336 | G4double x1 = 1. - cosTetMinNuc + screenZ; |
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337 | G4double x2 = 1. - costm + screenZ; |
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338 | G4double x3 = cosTetMinNuc - costm; |
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339 | G4double grej, z1; |
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340 | do { |
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341 | z1 = x1*x2/(x1 + G4UniformRand()*x3) - screenZ; |
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342 | grej = 1.0/(1.0 + formf*z1); |
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343 | } while ( G4UniformRand() > grej*grej ); |
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344 | |
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345 | //G4cout << "z= " << z1 << " cross= " << nucXSection/barn |
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346 | // << " crossE= " << elecXSection/barn << G4endl; |
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347 | |
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348 | return 1.0 - z1; |
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349 | } |
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350 | |
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351 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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352 | |
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353 | |
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