[968] | 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: G4LivermoreGammaConversionModel.cc,v 1.8 2009/06/11 15:47:08 mantero Exp $ |
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[1228] | 27 | // GEANT4 tag $Name: geant4-09-03 $ |
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[968] | 28 | // |
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[1055] | 29 | // |
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| 30 | // Author: Sebastien Inserti |
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| 31 | // 30 October 2008 |
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| 32 | // |
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| 33 | // History: |
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| 34 | // -------- |
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| 35 | // 12 Apr 2009 V Ivanchenko Cleanup initialisation and generation of secondaries: |
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| 36 | // - apply internal high-energy limit only in constructor |
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| 37 | // - do not apply low-energy limit (default is 0) |
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| 38 | // - use CLHEP electron mass for low-enegry limit |
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| 39 | // - remove MeanFreePath method and table |
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[968] | 40 | |
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[1055] | 41 | |
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[968] | 42 | #include "G4LivermoreGammaConversionModel.hh" |
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| 43 | |
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| 44 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 45 | |
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| 46 | using namespace std; |
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| 47 | |
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| 48 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 49 | |
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| 50 | G4LivermoreGammaConversionModel::G4LivermoreGammaConversionModel(const G4ParticleDefinition*, |
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[1055] | 51 | const G4String& nam) |
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| 52 | :G4VEmModel(nam),smallEnergy(2.*MeV),isInitialised(false), |
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| 53 | crossSectionHandler(0),meanFreePathTable(0) |
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[968] | 54 | { |
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[1055] | 55 | lowEnergyLimit = 2.0*electron_mass_c2; |
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[968] | 56 | highEnergyLimit = 100 * GeV; |
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[1055] | 57 | SetHighEnergyLimit(highEnergyLimit); |
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| 58 | |
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[968] | 59 | verboseLevel= 0; |
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| 60 | // Verbosity scale: |
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| 61 | // 0 = nothing |
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| 62 | // 1 = warning for energy non-conservation |
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| 63 | // 2 = details of energy budget |
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| 64 | // 3 = calculation of cross sections, file openings, sampling of atoms |
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| 65 | // 4 = entering in methods |
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| 66 | |
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[1055] | 67 | if(verboseLevel > 0) { |
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| 68 | G4cout << "Livermore Gamma conversion is constructed " << G4endl |
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| 69 | << "Energy range: " |
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| 70 | << lowEnergyLimit / MeV << " MeV - " |
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| 71 | << highEnergyLimit / GeV << " GeV" |
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| 72 | << G4endl; |
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| 73 | } |
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[968] | 74 | } |
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| 75 | |
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| 76 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 77 | |
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| 78 | G4LivermoreGammaConversionModel::~G4LivermoreGammaConversionModel() |
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| 79 | { |
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[1055] | 80 | if (crossSectionHandler) delete crossSectionHandler; |
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[968] | 81 | } |
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| 82 | |
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| 83 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 84 | |
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[1055] | 85 | void |
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| 86 | G4LivermoreGammaConversionModel::Initialise(const G4ParticleDefinition*, |
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| 87 | const G4DataVector&) |
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[968] | 88 | { |
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| 89 | if (verboseLevel > 3) |
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| 90 | G4cout << "Calling G4LivermoreGammaConversionModel::Initialise()" << G4endl; |
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| 91 | |
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[1055] | 92 | if (crossSectionHandler) |
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[968] | 93 | { |
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[1055] | 94 | crossSectionHandler->Clear(); |
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| 95 | delete crossSectionHandler; |
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[968] | 96 | } |
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| 97 | |
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| 98 | // Read data tables for all materials |
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| 99 | |
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| 100 | crossSectionHandler = new G4CrossSectionHandler(); |
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[1055] | 101 | crossSectionHandler->Initialise(0,lowEnergyLimit,100.*GeV,400); |
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[968] | 102 | G4String crossSectionFile = "pair/pp-cs-"; |
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| 103 | crossSectionHandler->LoadData(crossSectionFile); |
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| 104 | |
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| 105 | // |
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| 106 | |
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| 107 | if (verboseLevel > 2) |
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| 108 | G4cout << "Loaded cross section files for PenelopeGammaConversion" << G4endl; |
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| 109 | |
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[1055] | 110 | if (verboseLevel > 0) { |
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| 111 | G4cout << "Livermore Gamma Conversion model is initialized " << G4endl |
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| 112 | << "Energy range: " |
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| 113 | << LowEnergyLimit() / MeV << " MeV - " |
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| 114 | << HighEnergyLimit() / GeV << " GeV" |
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| 115 | << G4endl; |
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| 116 | } |
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[968] | 117 | |
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| 118 | if(isInitialised) return; |
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[1055] | 119 | fParticleChange = GetParticleChangeForGamma(); |
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| 120 | isInitialised = true; |
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| 121 | } |
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[968] | 122 | |
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| 123 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 124 | |
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[1055] | 125 | G4double |
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| 126 | G4LivermoreGammaConversionModel::ComputeCrossSectionPerAtom(const G4ParticleDefinition*, |
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| 127 | G4double GammaEnergy, |
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| 128 | G4double Z, G4double, |
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| 129 | G4double, G4double) |
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[968] | 130 | { |
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[1055] | 131 | if (verboseLevel > 3) { |
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| 132 | G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreGammaConversionModel" |
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| 133 | << G4endl; |
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| 134 | } |
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| 135 | if (GammaEnergy < lowEnergyLimit || GammaEnergy > highEnergyLimit) return 0; |
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[968] | 136 | |
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| 137 | G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy); |
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| 138 | return cs; |
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| 139 | } |
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| 140 | |
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| 141 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 142 | |
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| 143 | void G4LivermoreGammaConversionModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect, |
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| 144 | const G4MaterialCutsCouple* couple, |
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| 145 | const G4DynamicParticle* aDynamicGamma, |
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| 146 | G4double, |
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| 147 | G4double) |
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| 148 | { |
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| 149 | |
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| 150 | // The energies of the e+ e- secondaries are sampled using the Bethe - Heitler |
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| 151 | // cross sections with Coulomb correction. A modified version of the random |
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| 152 | // number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15). |
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| 153 | |
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| 154 | // Note 1 : Effects due to the breakdown of the Born approximation at low |
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| 155 | // energy are ignored. |
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| 156 | // Note 2 : The differential cross section implicitly takes account of |
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| 157 | // pair creation in both nuclear and atomic electron fields. However triplet |
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| 158 | // prodution is not generated. |
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| 159 | |
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| 160 | if (verboseLevel > 3) |
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| 161 | G4cout << "Calling SampleSecondaries() of G4LivermoreGammaConversionModel" << G4endl; |
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| 162 | |
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| 163 | G4double photonEnergy = aDynamicGamma->GetKineticEnergy(); |
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| 164 | G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection(); |
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| 165 | |
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| 166 | G4double epsilon ; |
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| 167 | G4double epsilon0 = electron_mass_c2 / photonEnergy ; |
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| 168 | |
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| 169 | // Do it fast if photon energy < 2. MeV |
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| 170 | if (photonEnergy < smallEnergy ) |
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| 171 | { |
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| 172 | epsilon = epsilon0 + (0.5 - epsilon0) * G4UniformRand(); |
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| 173 | } |
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| 174 | else |
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| 175 | { |
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| 176 | // Select randomly one element in the current material |
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[1055] | 177 | //const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy); |
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| 178 | const G4ParticleDefinition* particle = aDynamicGamma->GetDefinition(); |
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| 179 | const G4Element* element = SelectRandomAtom(couple,particle,photonEnergy); |
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[968] | 180 | |
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| 181 | if (element == 0) |
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| 182 | { |
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[1055] | 183 | G4cout << "G4LivermoreGammaConversionModel::SampleSecondaries - element = 0" |
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| 184 | << G4endl; |
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| 185 | return; |
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[968] | 186 | } |
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| 187 | G4IonisParamElm* ionisation = element->GetIonisation(); |
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[1055] | 188 | if (ionisation == 0) |
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[968] | 189 | { |
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[1055] | 190 | G4cout << "G4LivermoreGammaConversionModel::SampleSecondaries - ionisation = 0" |
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| 191 | << G4endl; |
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| 192 | return; |
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[968] | 193 | } |
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| 194 | |
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| 195 | // Extract Coulomb factor for this Element |
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| 196 | G4double fZ = 8. * (ionisation->GetlogZ3()); |
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| 197 | if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb()); |
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| 198 | |
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| 199 | // Limits of the screening variable |
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| 200 | G4double screenFactor = 136. * epsilon0 / (element->GetIonisation()->GetZ3()) ; |
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| 201 | G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ; |
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| 202 | G4double screenMin = std::min(4.*screenFactor,screenMax) ; |
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| 203 | |
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| 204 | // Limits of the energy sampling |
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| 205 | G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ; |
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| 206 | G4double epsilonMin = std::max(epsilon0,epsilon1); |
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| 207 | G4double epsilonRange = 0.5 - epsilonMin ; |
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| 208 | |
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| 209 | // Sample the energy rate of the created electron (or positron) |
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| 210 | G4double screen; |
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| 211 | G4double gReject ; |
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| 212 | |
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| 213 | G4double f10 = ScreenFunction1(screenMin) - fZ; |
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| 214 | G4double f20 = ScreenFunction2(screenMin) - fZ; |
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| 215 | G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.); |
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| 216 | G4double normF2 = std::max(1.5 * f20,0.); |
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| 217 | |
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| 218 | do { |
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| 219 | if (normF1 / (normF1 + normF2) > G4UniformRand() ) |
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| 220 | { |
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| 221 | epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.3333) ; |
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| 222 | screen = screenFactor / (epsilon * (1. - epsilon)); |
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| 223 | gReject = (ScreenFunction1(screen) - fZ) / f10 ; |
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| 224 | } |
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| 225 | else |
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| 226 | { |
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| 227 | epsilon = epsilonMin + epsilonRange * G4UniformRand(); |
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| 228 | screen = screenFactor / (epsilon * (1 - epsilon)); |
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| 229 | gReject = (ScreenFunction2(screen) - fZ) / f20 ; |
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| 230 | } |
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| 231 | } while ( gReject < G4UniformRand() ); |
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| 232 | |
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| 233 | } // End of epsilon sampling |
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| 234 | |
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| 235 | // Fix charges randomly |
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| 236 | |
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| 237 | G4double electronTotEnergy; |
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| 238 | G4double positronTotEnergy; |
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| 239 | |
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| 240 | if (CLHEP::RandBit::shootBit()) |
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| 241 | { |
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| 242 | electronTotEnergy = (1. - epsilon) * photonEnergy; |
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| 243 | positronTotEnergy = epsilon * photonEnergy; |
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| 244 | } |
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| 245 | else |
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| 246 | { |
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| 247 | positronTotEnergy = (1. - epsilon) * photonEnergy; |
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| 248 | electronTotEnergy = epsilon * photonEnergy; |
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| 249 | } |
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| 250 | |
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| 251 | // Scattered electron (positron) angles. ( Z - axis along the parent photon) |
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| 252 | // Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211), |
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| 253 | // derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977) |
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| 254 | |
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| 255 | G4double u; |
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| 256 | const G4double a1 = 0.625; |
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| 257 | G4double a2 = 3. * a1; |
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| 258 | // G4double d = 27. ; |
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| 259 | |
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| 260 | // if (9. / (9. + d) > G4UniformRand()) |
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| 261 | if (0.25 > G4UniformRand()) |
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| 262 | { |
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| 263 | u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ; |
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| 264 | } |
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| 265 | else |
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| 266 | { |
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| 267 | u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ; |
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| 268 | } |
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| 269 | |
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| 270 | G4double thetaEle = u*electron_mass_c2/electronTotEnergy; |
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| 271 | G4double thetaPos = u*electron_mass_c2/positronTotEnergy; |
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| 272 | G4double phi = twopi * G4UniformRand(); |
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| 273 | |
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| 274 | G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle); |
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| 275 | G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos); |
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| 276 | |
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| 277 | |
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| 278 | // Kinematics of the created pair: |
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| 279 | // the electron and positron are assumed to have a symetric angular |
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| 280 | // distribution with respect to the Z axis along the parent photon |
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| 281 | |
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| 282 | G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ; |
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| 283 | |
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[1055] | 284 | // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class |
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[968] | 285 | |
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| 286 | G4ThreeVector electronDirection (dxEle, dyEle, dzEle); |
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| 287 | electronDirection.rotateUz(photonDirection); |
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| 288 | |
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| 289 | G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(), |
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| 290 | electronDirection, |
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| 291 | electronKineEnergy); |
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| 292 | |
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| 293 | // The e+ is always created (even with kinetic energy = 0) for further annihilation |
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| 294 | G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ; |
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| 295 | |
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[1055] | 296 | // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class |
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[968] | 297 | |
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| 298 | G4ThreeVector positronDirection (dxPos, dyPos, dzPos); |
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| 299 | positronDirection.rotateUz(photonDirection); |
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| 300 | |
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| 301 | // Create G4DynamicParticle object for the particle2 |
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| 302 | G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(), |
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| 303 | positronDirection, positronKineEnergy); |
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| 304 | // Fill output vector |
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| 305 | fvect->push_back(particle1); |
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| 306 | fvect->push_back(particle2); |
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| 307 | |
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| 308 | // kill incident photon |
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| 309 | fParticleChange->SetProposedKineticEnergy(0.); |
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| 310 | fParticleChange->ProposeTrackStatus(fStopAndKill); |
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| 311 | |
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| 312 | } |
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| 313 | |
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| 314 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 315 | |
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| 316 | G4double G4LivermoreGammaConversionModel::ScreenFunction1(G4double screenVariable) |
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| 317 | { |
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| 318 | // Compute the value of the screening function 3*phi1 - phi2 |
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| 319 | |
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| 320 | G4double value; |
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| 321 | |
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| 322 | if (screenVariable > 1.) |
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| 323 | value = 42.24 - 8.368 * std::log(screenVariable + 0.952); |
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| 324 | else |
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| 325 | value = 42.392 - screenVariable * (7.796 - 1.961 * screenVariable); |
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| 326 | |
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| 327 | return value; |
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| 328 | } |
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| 329 | |
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| 330 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 331 | |
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| 332 | G4double G4LivermoreGammaConversionModel::ScreenFunction2(G4double screenVariable) |
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| 333 | { |
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| 334 | // Compute the value of the screening function 1.5*phi1 - 0.5*phi2 |
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| 335 | |
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| 336 | G4double value; |
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| 337 | |
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| 338 | if (screenVariable > 1.) |
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| 339 | value = 42.24 - 8.368 * std::log(screenVariable + 0.952); |
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| 340 | else |
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| 341 | value = 41.405 - screenVariable * (5.828 - 0.8945 * screenVariable); |
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| 342 | |
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| 343 | return value; |
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| 344 | } |
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| 345 | |
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