[1058] | 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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[1192] | 26 | // $Id: G4DNAScreenedRutherfordElasticModel.cc,v 1.9 2009/08/13 11:32:47 sincerti Exp $ |
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[1228] | 27 | // GEANT4 tag $Name: geant4-09-03 $ |
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[1058] | 28 | // |
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| 29 | |
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| 30 | #include "G4DNAScreenedRutherfordElasticModel.hh" |
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| 31 | |
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| 32 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 33 | |
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| 34 | using namespace std; |
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| 35 | |
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| 36 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 37 | |
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| 38 | G4DNAScreenedRutherfordElasticModel::G4DNAScreenedRutherfordElasticModel |
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| 39 | (const G4ParticleDefinition*, const G4String& nam) |
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| 40 | :G4VEmModel(nam),isInitialised(false) |
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| 41 | { |
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| 42 | |
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| 43 | killBelowEnergy = 8.23*eV; // Minimum e- energy for energy loss by excitation |
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| 44 | lowEnergyLimit = 0 * eV; |
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| 45 | lowEnergyLimitOfModel = 7 * eV; // The model lower energy is 7 eV |
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| 46 | intermediateEnergyLimit = 200 * eV; // Switch between two final state models |
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| 47 | highEnergyLimit = 10 * MeV; |
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| 48 | SetLowEnergyLimit(lowEnergyLimit); |
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| 49 | SetHighEnergyLimit(highEnergyLimit); |
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| 50 | |
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| 51 | verboseLevel= 0; |
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| 52 | // Verbosity scale: |
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| 53 | // 0 = nothing |
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| 54 | // 1 = warning for energy non-conservation |
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| 55 | // 2 = details of energy budget |
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| 56 | // 3 = calculation of cross sections, file openings, sampling of atoms |
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| 57 | // 4 = entering in methods |
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| 58 | |
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[1192] | 59 | if( verboseLevel>0 ) |
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| 60 | { |
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| 61 | G4cout << "Screened Rutherford Elastic model is constructed " << G4endl |
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| 62 | << "Energy range: " |
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| 63 | << lowEnergyLimit / eV << " eV - " |
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| 64 | << highEnergyLimit / MeV << " MeV" |
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| 65 | << G4endl; |
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| 66 | } |
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| 67 | |
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[1058] | 68 | } |
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| 69 | |
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| 70 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 71 | |
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| 72 | G4DNAScreenedRutherfordElasticModel::~G4DNAScreenedRutherfordElasticModel() |
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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 | void G4DNAScreenedRutherfordElasticModel::Initialise(const G4ParticleDefinition* /*particle*/, |
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| 78 | const G4DataVector& /*cuts*/) |
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| 79 | { |
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| 80 | |
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| 81 | if (verboseLevel > 3) |
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| 82 | G4cout << "Calling G4DNAScreenedRutherfordElasticModel::Initialise()" << G4endl; |
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| 83 | |
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| 84 | // Energy limits |
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| 85 | |
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| 86 | if (LowEnergyLimit() < lowEnergyLimit) |
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| 87 | { |
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| 88 | G4cout << "G4DNAScreenedRutherfordElasticModel: low energy limit increased from " << |
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| 89 | LowEnergyLimit()/eV << " eV to " << lowEnergyLimit/eV << " eV" << G4endl; |
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| 90 | SetLowEnergyLimit(lowEnergyLimit); |
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| 91 | } |
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| 92 | |
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| 93 | if (HighEnergyLimit() > highEnergyLimit) |
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| 94 | { |
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| 95 | G4cout << "G4DNAScreenedRutherfordElasticModel: high energy limit decreased from " << |
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| 96 | HighEnergyLimit()/MeV << " MeV to " << highEnergyLimit/MeV << " MeV" << G4endl; |
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| 97 | SetHighEnergyLimit(highEnergyLimit); |
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| 98 | } |
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| 99 | |
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| 100 | // Constants for final stae by Brenner & Zaider |
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| 101 | |
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| 102 | betaCoeff.push_back(7.51525); |
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| 103 | betaCoeff.push_back(-0.41912); |
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| 104 | betaCoeff.push_back(7.2017E-3); |
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| 105 | betaCoeff.push_back(-4.646E-5); |
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| 106 | betaCoeff.push_back(1.02897E-7); |
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| 107 | |
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| 108 | deltaCoeff.push_back(2.9612); |
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| 109 | deltaCoeff.push_back(-0.26376); |
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| 110 | deltaCoeff.push_back(4.307E-3); |
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| 111 | deltaCoeff.push_back(-2.6895E-5); |
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| 112 | deltaCoeff.push_back(5.83505E-8); |
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| 113 | |
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| 114 | gamma035_10Coeff.push_back(-1.7013); |
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| 115 | gamma035_10Coeff.push_back(-1.48284); |
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| 116 | gamma035_10Coeff.push_back(0.6331); |
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| 117 | gamma035_10Coeff.push_back(-0.10911); |
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| 118 | gamma035_10Coeff.push_back(8.358E-3); |
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| 119 | gamma035_10Coeff.push_back(-2.388E-4); |
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| 120 | |
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| 121 | gamma10_100Coeff.push_back(-3.32517); |
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| 122 | gamma10_100Coeff.push_back(0.10996); |
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| 123 | gamma10_100Coeff.push_back(-4.5255E-3); |
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| 124 | gamma10_100Coeff.push_back(5.8372E-5); |
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| 125 | gamma10_100Coeff.push_back(-2.4659E-7); |
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| 126 | |
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| 127 | gamma100_200Coeff.push_back(2.4775E-2); |
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| 128 | gamma100_200Coeff.push_back(-2.96264E-5); |
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| 129 | gamma100_200Coeff.push_back(-1.20655E-7); |
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| 130 | |
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| 131 | // |
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| 132 | |
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[1192] | 133 | if( verboseLevel>0 ) |
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| 134 | { |
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| 135 | G4cout << "Screened Rutherford elastic model is initialized " << G4endl |
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| 136 | << "Energy range: " |
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| 137 | << LowEnergyLimit() / eV << " eV - " |
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| 138 | << HighEnergyLimit() / MeV << " MeV" |
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| 139 | << G4endl; |
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| 140 | } |
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| 141 | |
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[1058] | 142 | if(!isInitialised) |
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| 143 | { |
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| 144 | isInitialised = true; |
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| 145 | |
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| 146 | if(pParticleChange) |
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| 147 | fParticleChangeForGamma = reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange); |
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| 148 | else |
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| 149 | fParticleChangeForGamma = new G4ParticleChangeForGamma(); |
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| 150 | } |
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| 151 | |
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| 152 | // InitialiseElementSelectors(particle,cuts); |
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| 153 | |
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| 154 | // Test if water material |
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| 155 | |
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| 156 | flagMaterialIsWater= false; |
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| 157 | densityWater = 0; |
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| 158 | |
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| 159 | const G4ProductionCutsTable* theCoupleTable = G4ProductionCutsTable::GetProductionCutsTable(); |
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| 160 | |
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| 161 | if(theCoupleTable) |
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| 162 | { |
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| 163 | G4int numOfCouples = theCoupleTable->GetTableSize(); |
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| 164 | |
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| 165 | if(numOfCouples>0) |
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| 166 | { |
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| 167 | for (G4int i=0; i<numOfCouples; i++) |
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| 168 | { |
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| 169 | const G4MaterialCutsCouple* couple = theCoupleTable->GetMaterialCutsCouple(i); |
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| 170 | const G4Material* material = couple->GetMaterial(); |
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| 171 | |
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[1192] | 172 | if (material->GetName() == "G4_WATER") |
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[1058] | 173 | { |
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[1192] | 174 | G4double density = material->GetAtomicNumDensityVector()[1]; |
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| 175 | flagMaterialIsWater = true; |
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| 176 | densityWater = density; |
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| 177 | |
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| 178 | if (verboseLevel > 3) |
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| 179 | G4cout << "****** Water material is found with density(cm^-3)=" << density/(cm*cm*cm) << G4endl; |
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[1058] | 180 | } |
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| 181 | |
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| 182 | } |
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| 183 | |
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[1192] | 184 | } // if(numOfCouples>0) |
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| 185 | |
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[1058] | 186 | } // if (theCoupleTable) |
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| 187 | |
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| 188 | } |
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| 189 | |
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| 190 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 191 | |
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| 192 | G4double G4DNAScreenedRutherfordElasticModel::CrossSectionPerVolume(const G4Material*, |
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| 193 | const G4ParticleDefinition*, |
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| 194 | G4double ekin, |
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| 195 | G4double, |
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| 196 | G4double) |
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| 197 | { |
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| 198 | if (verboseLevel > 3) |
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| 199 | G4cout << "Calling CrossSectionPerVolume() of G4DNAScreenedRutherfordElasticModel" << G4endl; |
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| 200 | |
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| 201 | // Calculate total cross section for model |
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| 202 | |
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| 203 | G4double sigma=0; |
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| 204 | |
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| 205 | if (flagMaterialIsWater) |
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| 206 | { |
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| 207 | |
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| 208 | if (ekin < highEnergyLimit) |
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| 209 | { |
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| 210 | |
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| 211 | //SI : XS must not be zero otherwise sampling of secondaries method ignored |
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| 212 | if (ekin < lowEnergyLimitOfModel) ekin = lowEnergyLimitOfModel; |
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| 213 | // |
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| 214 | |
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| 215 | G4double z = 10.; |
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| 216 | G4double n = ScreeningFactor(ekin,z); |
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| 217 | G4double crossSection = RutherfordCrossSection(ekin, z); |
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| 218 | sigma = pi * crossSection / (n * (n + 1.)); |
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| 219 | } |
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| 220 | |
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| 221 | if (verboseLevel > 3) |
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| 222 | { |
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| 223 | G4cout << "---> Kinetic energy(eV)=" << ekin/eV << G4endl; |
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| 224 | G4cout << " - Cross section per water molecule (cm^2)=" << sigma/cm/cm << G4endl; |
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| 225 | G4cout << " - Cross section per water molecule (cm^-1)=" << sigma*densityWater/(1./cm) << G4endl; |
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| 226 | } |
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| 227 | |
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| 228 | } // if (flagMaterialIsWater) |
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| 229 | |
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| 230 | return sigma*densityWater; |
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| 231 | } |
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| 232 | |
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| 233 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 234 | |
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| 235 | G4double G4DNAScreenedRutherfordElasticModel::RutherfordCrossSection(G4double k, G4double z) |
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| 236 | { |
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| 237 | // |
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| 238 | // e^4 / K + m_e c^2 \^2 |
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| 239 | // sigma_Ruth(K) = Z (Z+1) -------------------- | --------------------- | |
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| 240 | // (4 pi epsilon_0)^2 \ K * (K + 2 m_e c^2) / |
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| 241 | // |
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| 242 | // Where K is the electron non-relativistic kinetic energy |
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| 243 | // |
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| 244 | // NIM 155, pp. 145-156, 1978 |
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| 245 | |
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| 246 | G4double length =(e_squared * (k + electron_mass_c2)) / (4 * pi *epsilon0 * k * ( k + 2 * electron_mass_c2)); |
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| 247 | G4double cross = z * ( z + 1) * length * length; |
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| 248 | |
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| 249 | return cross; |
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| 250 | } |
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| 251 | |
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| 252 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 253 | |
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| 254 | G4double G4DNAScreenedRutherfordElasticModel::ScreeningFactor(G4double k, G4double z) |
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| 255 | { |
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| 256 | // |
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| 257 | // alpha_1 + beta_1 ln(K/eV) constK Z^(2/3) |
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| 258 | // n(T) = -------------------------- ----------------- |
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| 259 | // K/(m_e c^2) 2 + K/(m_e c^2) |
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| 260 | // |
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| 261 | // Where K is the electron non-relativistic kinetic energy |
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| 262 | // |
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| 263 | // n(T) > 0 for T < ~ 400 MeV |
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| 264 | // |
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| 265 | // NIM 155, pp. 145-156, 1978 |
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| 266 | // Formulae (2) and (5) |
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| 267 | |
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| 268 | const G4double alpha_1(1.64); |
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| 269 | const G4double beta_1(-0.0825); |
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| 270 | const G4double constK(1.7E-5); |
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| 271 | |
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| 272 | G4double numerator = (alpha_1 + beta_1 * std::log(k/eV)) * constK * std::pow(z, 2./3.); |
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| 273 | |
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| 274 | k /= electron_mass_c2; |
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| 275 | |
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| 276 | G4double denominator = k * (2 + k); |
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| 277 | |
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| 278 | G4double value = 0.; |
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| 279 | if (denominator > 0.) value = numerator / denominator; |
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| 280 | |
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| 281 | return value; |
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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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| 286 | void G4DNAScreenedRutherfordElasticModel::SampleSecondaries(std::vector<G4DynamicParticle*>* /*fvect*/, |
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| 287 | const G4MaterialCutsCouple* /*couple*/, |
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| 288 | const G4DynamicParticle* aDynamicElectron, |
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| 289 | G4double, |
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| 290 | G4double) |
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| 291 | { |
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| 292 | |
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| 293 | if (verboseLevel > 3) |
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| 294 | G4cout << "Calling SampleSecondaries() of G4DNAScreenedRutherfordElasticModel" << G4endl; |
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| 295 | |
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| 296 | G4double electronEnergy0 = aDynamicElectron->GetKineticEnergy(); |
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| 297 | |
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| 298 | if (electronEnergy0 < killBelowEnergy) |
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| 299 | { |
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| 300 | fParticleChangeForGamma->ProposeTrackStatus(fStopAndKill); |
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| 301 | fParticleChangeForGamma->ProposeLocalEnergyDeposit(electronEnergy0); |
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| 302 | return ; |
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| 303 | } |
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| 304 | |
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| 305 | G4double cosTheta = 0.; |
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| 306 | |
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| 307 | if (electronEnergy0>= killBelowEnergy && electronEnergy0 < highEnergyLimit) |
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| 308 | { |
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| 309 | if (electronEnergy0<intermediateEnergyLimit) |
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| 310 | { |
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| 311 | if (verboseLevel > 3) G4cout << "---> Using Brenner & Zaider model" << G4endl; |
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| 312 | cosTheta = BrennerZaiderRandomizeCosTheta(electronEnergy0); |
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| 313 | } |
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| 314 | |
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| 315 | if (electronEnergy0>=intermediateEnergyLimit) |
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| 316 | { |
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| 317 | if (verboseLevel > 3) G4cout << "---> Using Screened Rutherford model" << G4endl; |
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| 318 | G4double z = 10.; |
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| 319 | cosTheta = ScreenedRutherfordRandomizeCosTheta(electronEnergy0,z); |
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| 320 | } |
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| 321 | |
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| 322 | G4double phi = 2. * pi * G4UniformRand(); |
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| 323 | |
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| 324 | G4ThreeVector zVers = aDynamicElectron->GetMomentumDirection(); |
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| 325 | G4ThreeVector xVers = zVers.orthogonal(); |
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| 326 | G4ThreeVector yVers = zVers.cross(xVers); |
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| 327 | |
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| 328 | G4double xDir = std::sqrt(1. - cosTheta*cosTheta); |
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| 329 | G4double yDir = xDir; |
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| 330 | xDir *= std::cos(phi); |
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| 331 | yDir *= std::sin(phi); |
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| 332 | |
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| 333 | G4ThreeVector zPrimeVers((xDir*xVers + yDir*yVers + cosTheta*zVers)); |
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| 334 | |
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| 335 | fParticleChangeForGamma->ProposeMomentumDirection(zPrimeVers.unit()) ; |
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| 336 | |
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| 337 | fParticleChangeForGamma->SetProposedKineticEnergy(electronEnergy0); |
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| 338 | } |
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| 339 | |
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| 340 | } |
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| 341 | |
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| 342 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 343 | |
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| 344 | G4double G4DNAScreenedRutherfordElasticModel::BrennerZaiderRandomizeCosTheta(G4double k) |
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| 345 | { |
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| 346 | // d sigma_el 1 beta(K) |
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| 347 | // ------------ (K) ~ --------------------------------- + --------------------------------- |
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| 348 | // d Omega (1 + 2 gamma(K) - cos(theta))^2 (1 + 2 delta(K) + cos(theta))^2 |
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| 349 | // |
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| 350 | // Maximum is < 1/(4 gamma(K)^2) + beta(K)/((2+2delta(K))^2) |
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| 351 | // |
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| 352 | // Phys. Med. Biol. 29 N.4 (1983) 443-447 |
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| 353 | |
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| 354 | // gamma(K), beta(K) and delta(K) are polynomials with coefficients for energy measured in eV |
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| 355 | |
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| 356 | k /= eV; |
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| 357 | |
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| 358 | G4double beta = std::exp(CalculatePolynomial(k,betaCoeff)); |
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| 359 | G4double delta = std::exp(CalculatePolynomial(k,deltaCoeff)); |
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| 360 | G4double gamma; |
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| 361 | |
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| 362 | if (k > 100.) |
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| 363 | { |
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| 364 | gamma = CalculatePolynomial(k, gamma100_200Coeff); |
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| 365 | // Only in this case it is not the exponent of the polynomial |
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| 366 | } |
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| 367 | else |
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| 368 | { |
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| 369 | if (k>10) |
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| 370 | { |
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| 371 | gamma = std::exp(CalculatePolynomial(k, gamma10_100Coeff)); |
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| 372 | } |
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| 373 | else |
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| 374 | { |
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| 375 | gamma = std::exp(CalculatePolynomial(k, gamma035_10Coeff)); |
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| 376 | } |
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| 377 | } |
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| 378 | |
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| 379 | // ***** Original method |
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| 380 | |
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| 381 | G4double oneOverMax = 1. / (1./(4.*gamma*gamma) + beta/( (2.+2.*delta)*(2.+2.*delta) )); |
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| 382 | |
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| 383 | G4double cosTheta = 0.; |
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| 384 | G4double leftDenominator = 0.; |
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| 385 | G4double rightDenominator = 0.; |
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| 386 | G4double fCosTheta = 0.; |
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| 387 | |
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| 388 | do |
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| 389 | { |
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| 390 | cosTheta = 2. * G4UniformRand() - 1.; |
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| 391 | |
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| 392 | leftDenominator = (1. + 2.*gamma - cosTheta); |
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| 393 | rightDenominator = (1. + 2.*delta + cosTheta); |
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| 394 | if ( (leftDenominator * rightDenominator) != 0. ) |
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| 395 | { |
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| 396 | fCosTheta = oneOverMax * (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator)); |
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| 397 | } |
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| 398 | } |
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| 399 | while (fCosTheta < G4UniformRand()); |
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| 400 | |
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| 401 | return cosTheta; |
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| 402 | |
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| 403 | // ***** Alternative method using cumulative probability |
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| 404 | /* |
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| 405 | G4double cosTheta = -1; |
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| 406 | G4double cumul = 0; |
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| 407 | G4double value = 0; |
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| 408 | G4double leftDenominator = 0.; |
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| 409 | G4double rightDenominator = 0.; |
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| 410 | |
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| 411 | // Number of integration steps in the -1,1 range |
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| 412 | G4int iMax=200; |
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| 413 | |
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| 414 | G4double random = G4UniformRand(); |
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| 415 | |
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| 416 | // Cumulate differential cross section |
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| 417 | for (G4int i=0; i<iMax; i++) |
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| 418 | { |
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| 419 | cosTheta = -1 + i*2./(iMax-1); |
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| 420 | leftDenominator = (1. + 2.*gamma - cosTheta); |
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| 421 | rightDenominator = (1. + 2.*delta + cosTheta); |
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| 422 | if ( (leftDenominator * rightDenominator) != 0. ) |
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| 423 | { |
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| 424 | cumul = cumul + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator)); |
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| 425 | } |
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| 426 | } |
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| 427 | |
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| 428 | // Select cosTheta |
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| 429 | for (G4int i=0; i<iMax; i++) |
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| 430 | { |
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| 431 | cosTheta = -1 + i*2./(iMax-1); |
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| 432 | leftDenominator = (1. + 2.*gamma - cosTheta); |
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| 433 | rightDenominator = (1. + 2.*delta + cosTheta); |
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| 434 | if (cumul !=0 && (leftDenominator * rightDenominator) != 0.) |
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| 435 | value = value + (1./(leftDenominator*leftDenominator) + beta/(rightDenominator*rightDenominator)) / cumul; |
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| 436 | if (random < value) break; |
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| 437 | } |
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| 438 | |
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| 439 | return cosTheta; |
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| 440 | */ |
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| 441 | |
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| 442 | } |
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| 443 | |
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| 444 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 445 | |
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| 446 | G4double G4DNAScreenedRutherfordElasticModel::CalculatePolynomial(G4double k, std::vector<G4double>& vec) |
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| 447 | { |
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| 448 | // Sum_{i=0}^{size-1} vector_i k^i |
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| 449 | // |
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| 450 | // Phys. Med. Biol. 29 N.4 (1983) 443-447 |
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| 451 | |
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| 452 | G4double result = 0.; |
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| 453 | size_t size = vec.size(); |
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| 454 | |
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| 455 | while (size>0) |
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| 456 | { |
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| 457 | size--; |
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| 458 | |
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| 459 | result *= k; |
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| 460 | result += vec[size]; |
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| 461 | } |
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| 462 | |
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| 463 | return result; |
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| 464 | } |
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| 465 | |
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| 466 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 467 | |
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| 468 | G4double G4DNAScreenedRutherfordElasticModel::ScreenedRutherfordRandomizeCosTheta(G4double k, G4double z) |
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| 469 | { |
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| 470 | |
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| 471 | // d sigma_el sigma_Ruth(K) |
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| 472 | // ------------ (K) ~ ----------------------------- |
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| 473 | // d Omega (1 + 2 n(K) - cos(theta))^2 |
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| 474 | // |
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| 475 | // We extract cos(theta) distributed as (1 + 2 n(K) - cos(theta))^-2 |
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| 476 | // |
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| 477 | // Maximum is for theta=0: 1/(4 n(K)^2) (When n(K) is positive, that is always satisfied within the validity of the process) |
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| 478 | // |
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| 479 | // Phys. Med. Biol. 45 (2000) 3171-3194 |
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| 480 | |
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| 481 | // ***** Original method |
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| 482 | |
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| 483 | G4double n = ScreeningFactor(k, z); |
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| 484 | |
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| 485 | G4double oneOverMax = (4.*n*n); |
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| 486 | |
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| 487 | G4double cosTheta = 0.; |
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| 488 | G4double fCosTheta; |
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| 489 | |
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| 490 | do |
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| 491 | { |
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| 492 | cosTheta = 2. * G4UniformRand() - 1.; |
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| 493 | fCosTheta = (1 + 2.*n - cosTheta); |
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| 494 | if (fCosTheta !=0.) fCosTheta = oneOverMax / (fCosTheta*fCosTheta); |
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| 495 | } |
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| 496 | while (fCosTheta < G4UniformRand()); |
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| 497 | |
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| 498 | return cosTheta; |
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| 499 | |
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| 500 | // ***** Alternative method using cumulative probability |
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| 501 | /* |
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| 502 | G4double cosTheta = -1; |
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| 503 | G4double cumul = 0; |
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| 504 | G4double value = 0; |
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| 505 | G4double n = ScreeningFactor(k, z); |
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| 506 | G4double fCosTheta; |
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| 507 | |
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| 508 | // Number of integration steps in the -1,1 range |
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| 509 | G4int iMax=200; |
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| 510 | |
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| 511 | G4double random = G4UniformRand(); |
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| 512 | |
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| 513 | // Cumulate differential cross section |
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| 514 | for (G4int i=0; i<iMax; i++) |
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| 515 | { |
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| 516 | cosTheta = -1 + i*2./(iMax-1); |
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| 517 | fCosTheta = (1 + 2.*n - cosTheta); |
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| 518 | if (fCosTheta !=0.) cumul = cumul + 1./(fCosTheta*fCosTheta); |
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| 519 | } |
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| 520 | |
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| 521 | // Select cosTheta |
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| 522 | for (G4int i=0; i<iMax; i++) |
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| 523 | { |
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| 524 | cosTheta = -1 + i*2./(iMax-1); |
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| 525 | fCosTheta = (1 + 2.*n - cosTheta); |
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| 526 | if (cumul !=0.) value = value + (1./(fCosTheta*fCosTheta)) / cumul; |
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| 527 | if (random < value) break; |
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| 528 | } |
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| 529 | return cosTheta; |
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| 530 | */ |
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| 531 | } |
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| 532 | |
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