1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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7 | // * conditions of the Geant4 Software License, included in the file * |
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8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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9 | // * include a list of copyright holders. * |
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10 | // * * |
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11 | // * Neither the authors of this software system, nor their employing * |
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12 | // * institutes,nor the agencies providing financial support for this * |
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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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21 | // * any work based on the software) you agree to acknowledge its * |
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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 | // |
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27 | //////////////////////////////////////////////////////////////////////// |
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28 | // |
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29 | // File G4OpMieHG.hh |
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30 | // Description: Discrete Process -- Mie Scattering of Optical Photons |
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31 | // Created: 2010-07-03 |
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32 | // Author: Xin Qian |
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33 | // Based on work from Vlasios Vasileiou |
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34 | // |
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35 | // This subroutine will mimic the Mie scattering based on |
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36 | // Henyey-Greenstein phase function |
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37 | // Forward and backward angles are treated separately. |
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38 | // |
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39 | // mail: gum@triumf.ca |
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40 | // |
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41 | //////////////////////////////////////////////////////////////////////// |
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42 | |
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43 | #include "G4OpProcessSubType.hh" |
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44 | |
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45 | #include "G4OpMieHG.hh" |
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46 | |
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47 | G4OpMieHG::G4OpMieHG(const G4String& processName, G4ProcessType type) |
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48 | : G4VDiscreteProcess(processName, type) |
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49 | { |
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50 | if (verboseLevel>0) { |
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51 | G4cout << GetProcessName() << " is created " << G4endl; |
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52 | } |
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53 | |
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54 | SetProcessSubType(fOpMieHG); |
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55 | } |
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56 | |
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57 | G4OpMieHG::~G4OpMieHG(){} |
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58 | |
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59 | //////////// |
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60 | // Methods |
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61 | //////////// |
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62 | |
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63 | // PostStepDoIt |
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64 | // ------------- |
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65 | // |
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66 | G4VParticleChange* |
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67 | G4OpMieHG::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep) |
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68 | { |
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69 | aParticleChange.Initialize(aTrack); |
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70 | |
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71 | const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle(); |
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72 | const G4Material* aMaterial = aTrack.GetMaterial(); |
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73 | G4MaterialPropertiesTable* aMaterialPropertyTable = |
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74 | aMaterial->GetMaterialPropertiesTable(); |
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75 | |
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76 | G4double forward_g = |
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77 | aMaterialPropertyTable->GetConstProperty("MIEHG_FORWARD"); |
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78 | G4double backward_g = |
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79 | aMaterialPropertyTable->GetConstProperty("MIEHG_BACKWARD"); |
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80 | G4double ForwardRatio = |
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81 | aMaterialPropertyTable->GetConstProperty("MIEHG_FORWARD_RATIO"); |
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82 | |
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83 | if (verboseLevel>0) { |
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84 | G4cout << "MIE Scattering Photon!" << G4endl; |
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85 | G4cout << "MIE Old Momentum Direction: " |
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86 | << aParticle->GetMomentumDirection() << G4endl; |
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87 | G4cout << "MIE Old Polarization: " |
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88 | << aParticle->GetPolarization() << G4endl; |
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89 | } |
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90 | |
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91 | G4double g; |
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92 | G4int direction; |
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93 | if (G4UniformRand()<=ForwardRatio){ |
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94 | g = forward_g; |
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95 | direction = 1; |
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96 | } else { |
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97 | g = backward_g; |
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98 | direction = -1; |
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99 | } |
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100 | |
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101 | G4double r = G4UniformRand(); |
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102 | |
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103 | G4double Theta; |
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104 | //sample the direction |
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105 | if (g!=0) { |
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106 | Theta = std::acos(2*r*(1+g)*(1+g)*(1-g+g*r)/((1-g+2*g*r)*(1-g+2*g*r)) -1); |
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107 | } else { |
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108 | Theta = std::acos(2*r-1.); |
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109 | } |
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110 | G4double Phi = G4UniformRand()*2*pi; |
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111 | |
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112 | if (direction==-1) Theta = pi - Theta; //backward scattering |
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113 | |
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114 | G4ThreeVector NewMomentumDirection, OldMomentumDirection; |
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115 | G4ThreeVector OldPolarization, NewPolarization; |
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116 | |
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117 | NewMomentumDirection.set |
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118 | (std::sin(Theta)*std::cos(Phi), std::sin(Theta)*std::sin(Phi), std::cos(Theta)); |
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119 | OldMomentumDirection = aParticle->GetMomentumDirection(); |
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120 | NewMomentumDirection.rotateUz(OldMomentumDirection); |
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121 | NewMomentumDirection = NewMomentumDirection.unit(); |
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122 | |
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123 | OldPolarization = aParticle->GetPolarization(); |
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124 | G4double constant = -1./NewMomentumDirection.dot(OldPolarization); |
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125 | |
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126 | NewPolarization = NewMomentumDirection + constant*OldPolarization; |
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127 | NewPolarization = NewPolarization.unit(); |
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128 | |
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129 | if (NewPolarization.mag()==0) { |
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130 | r = G4UniformRand()*twopi; |
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131 | NewPolarization.set(std::cos(r),std::sin(r),0.); |
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132 | NewPolarization.rotateUz(NewMomentumDirection); |
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133 | } else { |
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134 | // There are two directions which perpendicular |
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135 | // new momentum direction |
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136 | if (G4UniformRand() < 0.5) NewPolarization = -NewPolarization; |
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137 | } |
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138 | |
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139 | aParticleChange.ProposePolarization(NewPolarization); |
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140 | aParticleChange.ProposeMomentumDirection(NewMomentumDirection); |
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141 | |
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142 | if (verboseLevel>0) { |
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143 | G4cout << "MIE New Polarization: " |
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144 | << NewPolarization << G4endl; |
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145 | G4cout << "MIE Polarization Change: " |
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146 | << *(aParticleChange.GetPolarization()) << G4endl; |
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147 | G4cout << "MIE New Momentum Direction: " |
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148 | << NewMomentumDirection << G4endl; |
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149 | G4cout << "MIE Momentum Change: " |
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150 | << *(aParticleChange.GetMomentumDirection()) << G4endl; |
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151 | } |
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152 | |
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153 | return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep); |
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154 | } |
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155 | |
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156 | // GetMeanFreePath() |
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157 | // ----------------- |
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158 | // |
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159 | G4double G4OpMieHG::GetMeanFreePath(const G4Track& aTrack, |
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160 | G4double , |
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161 | G4ForceCondition* ) |
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162 | { |
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163 | const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle(); |
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164 | const G4Material* aMaterial = aTrack.GetMaterial(); |
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165 | |
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166 | G4double thePhotonEnergy = aParticle->GetTotalEnergy(); |
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167 | |
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168 | G4double AttenuationLength = DBL_MAX; |
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169 | |
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170 | G4MaterialPropertiesTable* aMaterialPropertyTable = |
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171 | aMaterial->GetMaterialPropertiesTable(); |
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172 | |
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173 | if (aMaterialPropertyTable) { |
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174 | G4MaterialPropertyVector* AttenuationLengthVector = |
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175 | aMaterialPropertyTable->GetProperty("MIEHG"); |
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176 | if (AttenuationLengthVector) { |
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177 | AttenuationLength = AttenuationLengthVector -> |
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178 | GetProperty(thePhotonEnergy); |
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179 | } else { |
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180 | // G4cout << "No Mie scattering length specified" << G4endl; |
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181 | } |
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182 | } else { |
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183 | // G4cout << "No Mie scattering length specified" << G4endl; |
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184 | } |
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185 | |
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186 | // G4cout << thePhotonEnergy/GeV << " \t" << AttenuationLength/m << G4endl; |
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187 | |
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188 | return AttenuationLength; |
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189 | } |
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