[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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[1055] | 26 | // $Id: G4PenelopeAnnihilationModel.cc,v 1.3 2009/04/17 10:29:20 vnivanch Exp $ |
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| 27 | // GEANT4 tag $Name: geant4-09-03-beta-cand-01 $ |
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[968] | 28 | // |
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| 29 | // Author: Luciano Pandola |
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| 30 | // |
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| 31 | // History: |
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| 32 | // -------- |
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| 33 | // 29 Oct 2008 L Pandola Migration from process to model |
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[1055] | 34 | // 15 Apr 2009 V Ivanchenko Cleanup initialisation and generation of secondaries: |
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| 35 | // - apply internal high-energy limit only in constructor |
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| 36 | // - do not apply low-energy limit (default is 0) |
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| 37 | // - do not use G4ElementSelector |
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[968] | 38 | |
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| 39 | #include "G4PenelopeAnnihilationModel.hh" |
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| 40 | #include "G4ParticleDefinition.hh" |
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| 41 | #include "G4MaterialCutsCouple.hh" |
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| 42 | #include "G4ProductionCutsTable.hh" |
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| 43 | #include "G4DynamicParticle.hh" |
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| 44 | #include "G4Gamma.hh" |
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| 45 | |
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| 46 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 47 | |
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| 48 | |
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| 49 | G4PenelopeAnnihilationModel::G4PenelopeAnnihilationModel(const G4ParticleDefinition*, |
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| 50 | const G4String& nam) |
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| 51 | :G4VEmModel(nam),isInitialised(false) |
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| 52 | { |
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[1055] | 53 | fIntrinsicLowEnergyLimit = 0.0; |
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[968] | 54 | fIntrinsicHighEnergyLimit = 100.0*GeV; |
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[1055] | 55 | // SetLowEnergyLimit(fIntrinsicLowEnergyLimit); |
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[968] | 56 | SetHighEnergyLimit(fIntrinsicHighEnergyLimit); |
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| 57 | |
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| 58 | //Calculate variable that will be used later on |
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| 59 | fPielr2 = pi*classic_electr_radius*classic_electr_radius; |
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| 60 | |
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| 61 | verboseLevel= 0; |
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| 62 | // Verbosity scale: |
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| 63 | // 0 = nothing |
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| 64 | // 1 = warning for energy non-conservation |
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| 65 | // 2 = details of energy budget |
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| 66 | // 3 = calculation of cross sections, file openings, sampling of atoms |
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| 67 | // 4 = entering in methods |
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| 68 | |
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| 69 | } |
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| 70 | |
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| 71 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 72 | |
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| 73 | G4PenelopeAnnihilationModel::~G4PenelopeAnnihilationModel() |
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| 74 | {;} |
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| 75 | |
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| 76 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 77 | |
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[1055] | 78 | void G4PenelopeAnnihilationModel::Initialise(const G4ParticleDefinition*, |
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| 79 | const G4DataVector&) |
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[968] | 80 | { |
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| 81 | if (verboseLevel > 3) |
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| 82 | G4cout << "Calling G4PenelopeAnnihilationModel::Initialise()" << G4endl; |
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| 83 | |
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[1055] | 84 | if(verboseLevel > 0) { |
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| 85 | G4cout << "Penelope Annihilation model is initialized " << G4endl |
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| 86 | << "Energy range: " |
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| 87 | << LowEnergyLimit() / keV << " keV - " |
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| 88 | << HighEnergyLimit() / GeV << " GeV" |
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| 89 | << G4endl; |
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| 90 | } |
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[968] | 91 | |
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| 92 | if(isInitialised) return; |
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[1055] | 93 | fParticleChange = GetParticleChangeForGamma(); |
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[968] | 94 | isInitialised = true; |
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| 95 | } |
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| 96 | |
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| 97 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 98 | |
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| 99 | G4double G4PenelopeAnnihilationModel::ComputeCrossSectionPerAtom( |
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| 100 | const G4ParticleDefinition*, |
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| 101 | G4double energy, |
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| 102 | G4double Z, G4double, |
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| 103 | G4double, G4double) |
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| 104 | { |
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| 105 | if (verboseLevel > 3) |
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| 106 | G4cout << "Calling ComputeCrossSectionPerAtom() of G4PenelopeAnnihilationModel" << |
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| 107 | G4endl; |
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| 108 | |
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| 109 | G4double cs = Z*ComputeCrossSectionPerElectron(energy); |
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| 110 | |
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| 111 | if (verboseLevel > 2) |
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| 112 | G4cout << "Annihilation cross Section at " << energy/keV << " keV for Z=" << Z << |
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| 113 | " = " << cs/barn << " barn" << G4endl; |
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| 114 | return cs; |
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| 115 | } |
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| 116 | |
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| 117 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 118 | |
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| 119 | void G4PenelopeAnnihilationModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect, |
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| 120 | const G4MaterialCutsCouple*, |
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| 121 | const G4DynamicParticle* aDynamicPositron, |
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| 122 | G4double, |
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| 123 | G4double) |
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| 124 | { |
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| 125 | // |
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| 126 | // Penelope model to sample final state for positron annihilation. |
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| 127 | // Target eletrons are assumed to be free and at rest. Binding effects enabling |
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| 128 | // one-photon annihilation are neglected. |
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| 129 | // For annihilation at rest, two back-to-back photons are emitted, having energy of 511 keV |
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| 130 | // and isotropic angular distribution. |
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| 131 | // For annihilation in flight, it is used the theory from |
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| 132 | // W. Heitler, The quantum theory of radiation, Oxford University Press (1954) |
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| 133 | // The two photons can have different energy. The efficiency of the sampling algorithm |
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| 134 | // of the photon energy from the dSigma/dE distribution is practically 100% for |
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| 135 | // positrons of kinetic energy < 10 keV. It reaches a minimum (about 80%) at energy |
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| 136 | // of about 10 MeV. |
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| 137 | // The angle theta is kinematically linked to the photon energy, to ensure momentum |
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| 138 | // conservation. The angle phi is sampled isotropically for the first gamma. |
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| 139 | // |
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| 140 | if (verboseLevel > 3) |
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| 141 | G4cout << "Calling SamplingSecondaries() of G4PenelopeAnnihilationModel" << G4endl; |
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| 142 | |
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| 143 | G4double kineticEnergy = aDynamicPositron->GetKineticEnergy(); |
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[1055] | 144 | |
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| 145 | // kill primary |
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| 146 | fParticleChange->SetProposedKineticEnergy(0.); |
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| 147 | fParticleChange->ProposeTrackStatus(fStopAndKill); |
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[968] | 148 | |
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[1055] | 149 | if (kineticEnergy == 0.0) |
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[968] | 150 | { |
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| 151 | //Old AtRestDoIt |
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| 152 | G4double cosTheta = -1.0+2.0*G4UniformRand(); |
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| 153 | G4double sinTheta = std::sqrt(1.0-cosTheta*cosTheta); |
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| 154 | G4double phi = twopi*G4UniformRand(); |
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| 155 | G4ThreeVector direction (sinTheta*std::cos(phi),sinTheta*std::sin(phi),cosTheta); |
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| 156 | G4DynamicParticle* firstGamma = new G4DynamicParticle (G4Gamma::Gamma(), |
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| 157 | direction, electron_mass_c2); |
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| 158 | G4DynamicParticle* secondGamma = new G4DynamicParticle (G4Gamma::Gamma(), |
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| 159 | -direction, electron_mass_c2); |
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| 160 | |
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| 161 | fvect->push_back(firstGamma); |
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| 162 | fvect->push_back(secondGamma); |
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| 163 | return; |
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| 164 | } |
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| 165 | |
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| 166 | //This is the "PostStep" case (annihilation in flight) |
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| 167 | G4ParticleMomentum positronDirection = |
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| 168 | aDynamicPositron->GetMomentumDirection(); |
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| 169 | G4double gamma = 1.0 + std::max(kineticEnergy,1.0*eV)/electron_mass_c2; |
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| 170 | G4double gamma21 = std::sqrt(gamma*gamma-1); |
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| 171 | G4double ani = 1.0+gamma; |
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| 172 | G4double chimin = 1.0/(ani+gamma21); |
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| 173 | G4double rchi = (1.0-chimin)/chimin; |
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| 174 | G4double gt0 = ani*ani-2.0; |
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| 175 | G4double test=0.0; |
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| 176 | G4double epsilon = 0; |
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| 177 | do{ |
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| 178 | epsilon = chimin*std::pow(rchi,G4UniformRand()); |
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| 179 | G4double reject = ani*ani*(1.0-epsilon)+2.0*gamma-(1.0/epsilon); |
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| 180 | test = G4UniformRand()*gt0-reject; |
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| 181 | }while(test>0); |
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| 182 | |
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| 183 | G4double totalAvailableEnergy = kineticEnergy + 2.0*electron_mass_c2; |
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| 184 | G4double photon1Energy = epsilon*totalAvailableEnergy; |
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| 185 | G4double photon2Energy = (1.0-epsilon)*totalAvailableEnergy; |
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| 186 | G4double cosTheta1 = (ani-1.0/epsilon)/gamma21; |
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| 187 | G4double cosTheta2 = (ani-1.0/(1.0-epsilon))/gamma21; |
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| 188 | |
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| 189 | //G4double localEnergyDeposit = 0.; |
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| 190 | |
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| 191 | G4double sinTheta1 = std::sqrt(1.-cosTheta1*cosTheta1); |
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| 192 | G4double phi1 = twopi * G4UniformRand(); |
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| 193 | G4double dirx1 = sinTheta1 * std::cos(phi1); |
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| 194 | G4double diry1 = sinTheta1 * std::sin(phi1); |
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| 195 | G4double dirz1 = cosTheta1; |
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| 196 | |
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| 197 | G4double sinTheta2 = std::sqrt(1.-cosTheta2*cosTheta2); |
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| 198 | G4double phi2 = phi1+pi; |
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| 199 | G4double dirx2 = sinTheta2 * std::cos(phi2); |
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| 200 | G4double diry2 = sinTheta2 * std::sin(phi2); |
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| 201 | G4double dirz2 = cosTheta2; |
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| 202 | |
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| 203 | G4ThreeVector photon1Direction (dirx1,diry1,dirz1); |
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| 204 | photon1Direction.rotateUz(positronDirection); |
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| 205 | // create G4DynamicParticle object for the particle1 |
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| 206 | G4DynamicParticle* aParticle1= new G4DynamicParticle (G4Gamma::Gamma(), |
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| 207 | photon1Direction, |
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| 208 | photon1Energy); |
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| 209 | fvect->push_back(aParticle1); |
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| 210 | |
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| 211 | G4ThreeVector photon2Direction(dirx2,diry2,dirz2); |
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| 212 | photon2Direction.rotateUz(positronDirection); |
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| 213 | // create G4DynamicParticle object for the particle2 |
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| 214 | G4DynamicParticle* aParticle2= new G4DynamicParticle (G4Gamma::Gamma(), |
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| 215 | photon2Direction, |
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| 216 | photon2Energy); |
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| 217 | fvect->push_back(aParticle2); |
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| 218 | |
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| 219 | if (verboseLevel > 1) |
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| 220 | { |
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| 221 | G4cout << "-----------------------------------------------------------" << G4endl; |
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| 222 | G4cout << "Energy balance from G4PenelopeAnnihilation" << G4endl; |
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| 223 | G4cout << "Kinetic positron energy: " << kineticEnergy/keV << " keV" << G4endl; |
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| 224 | G4cout << "Total available energy: " << totalAvailableEnergy/keV << " keV " << G4endl; |
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| 225 | G4cout << "-----------------------------------------------------------" << G4endl; |
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| 226 | G4cout << "Photon energy 1: " << photon1Energy/keV << " keV" << G4endl; |
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| 227 | G4cout << "Photon energy 2: " << photon2Energy/keV << " keV" << G4endl; |
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| 228 | G4cout << "Total final state: " << (photon1Energy+photon2Energy)/keV << |
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| 229 | " keV" << G4endl; |
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| 230 | G4cout << "-----------------------------------------------------------" << G4endl; |
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| 231 | } |
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| 232 | if (verboseLevel > 0) |
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[1055] | 233 | { |
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[968] | 234 | G4double energyDiff = std::fabs(totalAvailableEnergy-photon1Energy-photon2Energy); |
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| 235 | if (energyDiff > 0.05*keV) |
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| 236 | G4cout << "Warning from G4PenelopeAnnihilation: problem with energy conservation: " << |
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| 237 | (photon1Energy+photon2Energy)/keV << |
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| 238 | " keV (final) vs. " << |
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| 239 | totalAvailableEnergy/keV << " keV (initial)" << G4endl; |
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| 240 | } |
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| 241 | return; |
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| 242 | } |
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| 243 | |
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| 244 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 245 | |
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| 246 | G4double G4PenelopeAnnihilationModel:: ComputeCrossSectionPerElectron(G4double energy) |
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| 247 | { |
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| 248 | // |
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| 249 | // Penelope model to calculate cross section for positron annihilation. |
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| 250 | // The annihilation cross section per electron is calculated according |
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| 251 | // to the Heitler formula |
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| 252 | // W. Heitler, The quantum theory of radiation, Oxford University Press (1954) |
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| 253 | // in the assumptions of electrons free and at rest. |
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| 254 | // |
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| 255 | G4double gamma = 1.0+std::max(energy,1.0*eV)/electron_mass_c2; |
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| 256 | G4double gamma2 = gamma*gamma; |
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| 257 | G4double f2 = gamma2-1.0; |
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| 258 | G4double f1 = std::sqrt(f2); |
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| 259 | G4double crossSection = fPielr2*((gamma2+4.0*gamma+1.0)*std::log(gamma+f1)/f2 |
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| 260 | - (gamma+3.0)/f1)/(gamma+1.0); |
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| 261 | return crossSection; |
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| 262 | } |
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