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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4LivermorePolarizedRayleighModel.cc,v 1.5 2009/05/02 15:20:53 sincerti Exp $ |
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27 | // GEANT4 tag $Name: geant4-09-03 $ |
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28 | // |
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29 | // History: |
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30 | // -------- |
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31 | // 02 May 2009 S Incerti as V. Ivanchenko proposed in G4LivermoreRayleighModel.cc |
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32 | // |
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33 | // Cleanup initialisation and generation of secondaries: |
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34 | // - apply internal high-energy limit only in constructor |
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35 | // - do not apply low-energy limit (default is 0) |
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36 | // - remove GetMeanFreePath method and table |
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37 | // - remove initialisation of element selector |
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38 | // - use G4ElementSelector |
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39 | |
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40 | #include "G4LivermorePolarizedRayleighModel.hh" |
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41 | |
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42 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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43 | |
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44 | using namespace std; |
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45 | |
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46 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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47 | |
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48 | G4LivermorePolarizedRayleighModel::G4LivermorePolarizedRayleighModel(const G4ParticleDefinition*, |
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49 | const G4String& nam) |
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50 | :G4VEmModel(nam),isInitialised(false),crossSectionHandler(0),formFactorData(0) |
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51 | { |
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52 | lowEnergyLimit = 250 * eV; |
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53 | highEnergyLimit = 100 * GeV; |
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54 | |
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55 | //SetLowEnergyLimit(lowEnergyLimit); |
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56 | SetHighEnergyLimit(highEnergyLimit); |
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57 | // |
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58 | verboseLevel= 0; |
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59 | // Verbosity scale: |
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60 | // 0 = nothing |
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61 | // 1 = warning for energy non-conservation |
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62 | // 2 = details of energy budget |
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63 | // 3 = calculation of cross sections, file openings, sampling of atoms |
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64 | // 4 = entering in methods |
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65 | |
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66 | if(verboseLevel > 0) { |
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67 | G4cout << "Livermore Polarized Rayleigh is constructed " << G4endl |
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68 | << "Energy range: " |
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69 | << lowEnergyLimit / eV << " eV - " |
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70 | << highEnergyLimit / GeV << " GeV" |
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71 | << G4endl; |
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72 | } |
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73 | } |
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74 | |
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75 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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76 | |
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77 | G4LivermorePolarizedRayleighModel::~G4LivermorePolarizedRayleighModel() |
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78 | { |
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79 | if (crossSectionHandler) delete crossSectionHandler; |
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80 | if (formFactorData) delete formFactorData; |
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81 | } |
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82 | |
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83 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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84 | |
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85 | void G4LivermorePolarizedRayleighModel::Initialise(const G4ParticleDefinition* particle, |
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86 | const G4DataVector& cuts) |
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87 | { |
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88 | // Rayleigh process: The Quantum Theory of Radiation |
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89 | // W. Heitler, Oxford at the Clarendon Press, Oxford (1954) |
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90 | // Scattering function: A simple model of photon transport |
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91 | // D.E. Cullen, Nucl. Instr. Meth. in Phys. Res. B 101 (1995) 499-510 |
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92 | // Polarization of the outcoming photon: Beam test of a prototype detector array for the PoGO astronomical hard X-ray/soft gamma-ray polarimeter |
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93 | // T. Mizuno et al., Nucl. Instr. Meth. in Phys. Res. A 540 (2005) 158-168 |
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94 | |
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95 | if (verboseLevel > 3) |
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96 | G4cout << "Calling G4LivermorePolarizedRayleighModel::Initialise()" << G4endl; |
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97 | |
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98 | if (crossSectionHandler) |
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99 | { |
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100 | crossSectionHandler->Clear(); |
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101 | delete crossSectionHandler; |
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102 | } |
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103 | |
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104 | // Read data files for all materials |
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105 | |
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106 | crossSectionHandler = new G4CrossSectionHandler; |
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107 | crossSectionHandler->Clear(); |
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108 | G4String crossSectionFile = "rayl/re-cs-"; |
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109 | crossSectionHandler->LoadData(crossSectionFile); |
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110 | |
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111 | G4VDataSetAlgorithm* ffInterpolation = new G4LogLogInterpolation; |
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112 | G4String formFactorFile = "rayl/re-ff-"; |
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113 | formFactorData = new G4CompositeEMDataSet(ffInterpolation,1.,1.); |
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114 | formFactorData->LoadData(formFactorFile); |
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115 | |
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116 | InitialiseElementSelectors(particle,cuts); |
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117 | |
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118 | // |
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119 | if (verboseLevel > 2) |
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120 | G4cout << "Loaded cross section files for Livermore Polarized Rayleigh model" << G4endl; |
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121 | |
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122 | InitialiseElementSelectors(particle,cuts); |
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123 | |
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124 | if (verboseLevel > 0) { |
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125 | G4cout << "Livermore Polarized Rayleigh model is initialized " << G4endl |
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126 | << "Energy range: " |
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127 | << LowEnergyLimit() / eV << " eV - " |
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128 | << HighEnergyLimit() / GeV << " GeV" |
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129 | << G4endl; |
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130 | } |
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131 | |
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132 | if(isInitialised) return; |
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133 | fParticleChange = GetParticleChangeForGamma(); |
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134 | isInitialised = true; |
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135 | } |
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136 | |
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137 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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138 | |
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139 | G4double G4LivermorePolarizedRayleighModel::ComputeCrossSectionPerAtom( |
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140 | const G4ParticleDefinition*, |
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141 | G4double GammaEnergy, |
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142 | G4double Z, G4double, |
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143 | G4double, G4double) |
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144 | { |
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145 | if (verboseLevel > 3) |
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146 | G4cout << "Calling CrossSectionPerAtom() of G4LivermorePolarizedRayleighModel" << G4endl; |
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147 | |
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148 | if (GammaEnergy < lowEnergyLimit || GammaEnergy > highEnergyLimit) return 0.0; |
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149 | |
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150 | G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy); |
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151 | return cs; |
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152 | } |
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153 | |
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154 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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155 | |
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156 | void G4LivermorePolarizedRayleighModel::SampleSecondaries(std::vector<G4DynamicParticle*>* /*fvect*/, |
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157 | const G4MaterialCutsCouple* couple, |
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158 | const G4DynamicParticle* aDynamicGamma, |
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159 | G4double, |
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160 | G4double) |
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161 | { |
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162 | if (verboseLevel > 3) |
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163 | G4cout << "Calling SampleSecondaries() of G4LivermorePolarizedRayleighModel" << G4endl; |
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164 | |
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165 | G4double photonEnergy0 = aDynamicGamma->GetKineticEnergy(); |
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166 | |
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167 | if (photonEnergy0 <= lowEnergyLimit) |
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168 | { |
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169 | fParticleChange->ProposeTrackStatus(fStopAndKill); |
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170 | fParticleChange->SetProposedKineticEnergy(0.); |
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171 | fParticleChange->ProposeLocalEnergyDeposit(photonEnergy0); |
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172 | return ; |
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173 | } |
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174 | |
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175 | G4ParticleMomentum photonDirection0 = aDynamicGamma->GetMomentumDirection(); |
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176 | |
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177 | // Select randomly one element in the current material |
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178 | // G4int Z = crossSectionHandler->SelectRandomAtom(couple,photonEnergy0); |
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179 | const G4ParticleDefinition* particle = aDynamicGamma->GetDefinition(); |
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180 | const G4Element* elm = SelectRandomAtom(couple,particle,photonEnergy0); |
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181 | G4int Z = (G4int)elm->GetZ(); |
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182 | |
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183 | G4double outcomingPhotonCosTheta = GenerateCosTheta(photonEnergy0, Z); |
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184 | G4double outcomingPhotonPhi = GeneratePhi(outcomingPhotonCosTheta); |
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185 | G4double beta=GeneratePolarizationAngle(); |
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186 | |
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187 | // incomingPhoton reference frame: |
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188 | // z = versor parallel to the incomingPhotonDirection |
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189 | // x = versor parallel to the incomingPhotonPolarization |
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190 | // y = defined as z^x |
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191 | |
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192 | // outgoingPhoton reference frame: |
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193 | // z' = versor parallel to the outgoingPhotonDirection |
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194 | // x' = defined as x-x*z'z' normalized |
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195 | // y' = defined as z'^x' |
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196 | |
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197 | G4ThreeVector z(aDynamicGamma->GetMomentumDirection().unit()); |
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198 | G4ThreeVector x(GetPhotonPolarization(*aDynamicGamma)); |
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199 | G4ThreeVector y(z.cross(x)); |
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200 | |
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201 | // z' = std::cos(phi)*std::sin(theta) x + std::sin(phi)*std::sin(theta) y + std::cos(theta) z |
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202 | G4double xDir; |
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203 | G4double yDir; |
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204 | G4double zDir; |
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205 | zDir=outcomingPhotonCosTheta; |
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206 | xDir=std::sqrt(1-outcomingPhotonCosTheta*outcomingPhotonCosTheta); |
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207 | yDir=xDir; |
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208 | xDir*=std::cos(outcomingPhotonPhi); |
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209 | yDir*=std::sin(outcomingPhotonPhi); |
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210 | |
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211 | G4ThreeVector zPrime((xDir*x + yDir*y + zDir*z).unit()); |
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212 | G4ThreeVector xPrime(x.perpPart(zPrime).unit()); |
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213 | G4ThreeVector yPrime(zPrime.cross(xPrime)); |
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214 | |
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215 | // outgoingPhotonPolarization is directed as x' std::cos(beta) + y' std::sin(beta) |
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216 | G4ThreeVector outcomingPhotonPolarization(xPrime*std::cos(beta) + yPrime*std::sin(beta)); |
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217 | |
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218 | fParticleChange->ProposeMomentumDirection(zPrime); |
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219 | fParticleChange->ProposePolarization(outcomingPhotonPolarization); |
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220 | fParticleChange->SetProposedKineticEnergy(photonEnergy0); |
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221 | |
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222 | } |
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223 | |
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224 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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225 | |
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226 | G4double G4LivermorePolarizedRayleighModel::GenerateCosTheta(G4double incomingPhotonEnergy, G4int zAtom) const |
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227 | { |
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228 | // d sigma k0 |
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229 | // --------- = r0^2 * pi * F^2(x, Z) * ( 2 - sin^2 theta) * std::sin (theta), x = ---- std::sin(theta/2) |
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230 | // d theta hc |
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231 | |
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232 | // d sigma k0 1 - y |
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233 | // --------- = r0^2 * pi * F^2(x, Z) * ( 1 + y^2), x = ---- std::sqrt ( ------- ), y = std::cos(theta) |
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234 | // d y hc 2 |
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235 | |
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236 | // Z |
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237 | // F(x, Z) ~ -------- |
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238 | // a + bx |
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239 | // |
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240 | // The time to exit from the outer loop grows as ~ k0 |
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241 | // On pcgeant2 the time is ~ 1 s for k0 ~ 1 MeV on the oxygen element. A 100 GeV |
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242 | // event will take ~ 10 hours. |
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243 | // |
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244 | // On the avarage the inner loop does 1.5 iterations before exiting |
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245 | |
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246 | const G4double xFactor = (incomingPhotonEnergy*cm)/(h_Planck*c_light); |
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247 | //const G4VEMDataSet * formFactorData = GetScatterFunctionData(); |
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248 | |
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249 | G4double cosTheta; |
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250 | G4double fCosTheta; |
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251 | G4double x; |
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252 | G4double fValue; |
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253 | |
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254 | do |
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255 | { |
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256 | do |
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257 | { |
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258 | cosTheta = 2.*G4UniformRand()-1.; |
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259 | fCosTheta = (1.+cosTheta*cosTheta)/2.; |
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260 | } |
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261 | while (fCosTheta < G4UniformRand()); |
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262 | |
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263 | x = xFactor*std::sqrt((1.-cosTheta)/2.); |
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264 | |
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265 | if (x > 1.e+005) |
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266 | fValue = formFactorData->FindValue(x, zAtom-1); |
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267 | else |
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268 | fValue = formFactorData->FindValue(0., zAtom-1); |
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269 | |
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270 | fValue/=zAtom; |
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271 | fValue*=fValue; |
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272 | } |
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273 | while(fValue < G4UniformRand()); |
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274 | |
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275 | return cosTheta; |
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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 G4LivermorePolarizedRayleighModel::GeneratePhi(G4double cosTheta) const |
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281 | { |
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282 | // d sigma |
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283 | // --------- = alpha * ( 1 - sin^2 (theta) * cos^2 (phi) ) |
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284 | // d phi |
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285 | |
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286 | // On the average the loop takes no more than 2 iterations before exiting |
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287 | |
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288 | G4double phi; |
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289 | G4double cosPhi; |
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290 | G4double phiProbability; |
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291 | G4double sin2Theta; |
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292 | |
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293 | sin2Theta=1.-cosTheta*cosTheta; |
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294 | |
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295 | do |
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296 | { |
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297 | phi = twopi * G4UniformRand(); |
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298 | cosPhi = std::cos(phi); |
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299 | phiProbability= 1. - sin2Theta*cosPhi*cosPhi; |
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300 | } |
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301 | while (phiProbability < G4UniformRand()); |
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302 | |
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303 | return phi; |
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304 | } |
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305 | |
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306 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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307 | |
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308 | G4double G4LivermorePolarizedRayleighModel::GeneratePolarizationAngle(void) const |
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309 | { |
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310 | // Rayleigh polarization is always on the x' direction |
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311 | |
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312 | return 0; |
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313 | } |
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314 | |
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315 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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316 | |
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317 | G4ThreeVector G4LivermorePolarizedRayleighModel::GetPhotonPolarization(const G4DynamicParticle& photon) |
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318 | { |
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319 | |
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320 | // SI - From G4VLowEnergyDiscretePhotonProcess.cc |
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321 | |
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322 | G4ThreeVector photonMomentumDirection; |
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323 | G4ThreeVector photonPolarization; |
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324 | |
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325 | photonPolarization = photon.GetPolarization(); |
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326 | photonMomentumDirection = photon.GetMomentumDirection(); |
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327 | |
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328 | if ((!photonPolarization.isOrthogonal(photonMomentumDirection, 1e-6)) || photonPolarization.mag()==0.) |
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329 | { |
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330 | // if |photonPolarization|==0. or |photonPolarization * photonDirection0| > 1e-6 * |photonPolarization ^ photonDirection0| |
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331 | // then polarization is choosen randomly. |
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332 | |
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333 | G4ThreeVector e1(photonMomentumDirection.orthogonal().unit()); |
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334 | G4ThreeVector e2(photonMomentumDirection.cross(e1).unit()); |
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335 | |
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336 | G4double angle(G4UniformRand() * twopi); |
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337 | |
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338 | e1*=std::cos(angle); |
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339 | e2*=std::sin(angle); |
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340 | |
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341 | photonPolarization=e1+e2; |
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342 | } |
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343 | else if (photonPolarization.howOrthogonal(photonMomentumDirection) != 0.) |
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344 | { |
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345 | // if |photonPolarization * photonDirection0| != 0. |
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346 | // then polarization is made orthonormal; |
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347 | |
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348 | photonPolarization=photonPolarization.perpPart(photonMomentumDirection); |
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349 | } |
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350 | |
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351 | return photonPolarization.unit(); |
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352 | } |
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353 | |
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