[1350] | 1 | // |
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| 2 | // ******************************************************************** |
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| 3 | // * License and Disclaimer * |
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| 4 | // * * |
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| 5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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| 6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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| 7 | // * conditions of the Geant4 Software License, included in the file * |
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| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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| 9 | // * include a list of copyright holders. * |
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| 10 | // * * |
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| 11 | // * Neither the authors of this software system, nor their employing * |
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| 12 | // * institutes,nor the agencies providing financial support for this * |
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| 13 | // * work make any representation or warranty, express or implied, * |
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| 14 | // * regarding this software system or assume any liability for its * |
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| 15 | // * use. Please see the license in the file LICENSE and URL above * |
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| 16 | // * for the full disclaimer and the limitation of liability. * |
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| 17 | // * * |
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| 18 | // * This code implementation is the result of the scientific and * |
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| 19 | // * technical work of the GEANT4 collaboration. * |
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| 20 | // * By using, copying, modifying or distributing the software (or * |
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| 21 | // * any work based on the software) you agree to acknowledge its * |
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| 22 | // * use in resulting scientific publications, and indicate your * |
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| 23 | // * acceptance of all terms of the Geant4 Software license. * |
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| 24 | // ******************************************************************** |
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| 25 | // |
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| 26 | // $Id: G4KleinNishinaModel.cc,v 1.1 2010/09/03 14:11:16 vnivanch Exp $ |
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| 27 | // GEANT4 tag $Name: emstand-V09-03-24 $ |
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| 28 | // |
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| 29 | // ------------------------------------------------------------------- |
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| 30 | // |
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| 31 | // GEANT4 Class file |
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| 32 | // |
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| 33 | // |
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| 34 | // File name: G4KleinNishinaModel |
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| 35 | // |
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| 36 | // Author: Vladimir Ivanchenko on base of G4KleinNishinaCompton |
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| 37 | // |
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| 38 | // Creation date: 13.06.2010 |
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| 39 | // |
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| 40 | // Modifications: |
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| 41 | // |
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| 42 | // Class Description: |
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| 43 | // |
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| 44 | // ------------------------------------------------------------------- |
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| 45 | // |
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| 46 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 47 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 48 | |
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| 49 | #include "G4KleinNishinaModel.hh" |
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| 50 | #include "G4Electron.hh" |
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| 51 | #include "G4Gamma.hh" |
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| 52 | #include "Randomize.hh" |
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| 53 | #include "G4RandomDirection.hh" |
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| 54 | #include "G4DataVector.hh" |
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| 55 | #include "G4ParticleChangeForGamma.hh" |
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| 56 | #include "G4VAtomDeexcitation.hh" |
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| 57 | #include "G4LossTableManager.hh" |
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| 58 | |
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| 59 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 60 | |
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| 61 | using namespace std; |
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| 62 | |
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| 63 | G4KleinNishinaModel::G4KleinNishinaModel(const G4String& nam) |
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| 64 | : G4VEmModel(nam),isInitialized(false) |
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| 65 | { |
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| 66 | theGamma = G4Gamma::Gamma(); |
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| 67 | theElectron = G4Electron::Electron(); |
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| 68 | lowestGammaEnergy = 1.0*eV; |
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| 69 | fProbabilities.resize(9,0.0); |
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| 70 | } |
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| 71 | |
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| 72 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 73 | |
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| 74 | G4KleinNishinaModel::~G4KleinNishinaModel() |
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| 75 | {} |
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| 76 | |
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| 77 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 78 | |
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| 79 | void G4KleinNishinaModel::Initialise(const G4ParticleDefinition* p, |
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| 80 | const G4DataVector& cuts) |
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| 81 | { |
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| 82 | fAtomDeexcitation = G4LossTableManager::Instance()->AtomDeexcitation(); |
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| 83 | InitialiseElementSelectors(p, cuts); |
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| 84 | |
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| 85 | if (isInitialized) { return; } |
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| 86 | fParticleChange = GetParticleChangeForGamma(); |
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| 87 | isInitialized = true; |
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| 88 | } |
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| 89 | |
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| 90 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 91 | |
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| 92 | G4double |
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| 93 | G4KleinNishinaModel::ComputeCrossSectionPerAtom(const G4ParticleDefinition*, |
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| 94 | G4double GammaEnergy, |
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| 95 | G4double Z, G4double, |
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| 96 | G4double, G4double) |
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| 97 | { |
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| 98 | G4double CrossSection = 0.0 ; |
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| 99 | if ( Z < 0.9999 || GammaEnergy < 0.1*keV) { return CrossSection; } |
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| 100 | |
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| 101 | static const G4double a = 20.0 , b = 230.0 , c = 440.0; |
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| 102 | |
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| 103 | static const G4double |
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| 104 | d1= 2.7965e-1*barn, d2=-1.8300e-1*barn, d3= 6.7527 *barn, d4=-1.9798e+1*barn, |
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| 105 | e1= 1.9756e-5*barn, e2=-1.0205e-2*barn, e3=-7.3913e-2*barn, e4= 2.7079e-2*barn, |
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| 106 | f1=-3.9178e-7*barn, f2= 6.8241e-5*barn, f3= 6.0480e-5*barn, f4= 3.0274e-4*barn; |
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| 107 | |
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| 108 | G4double p1Z = Z*(d1 + e1*Z + f1*Z*Z), p2Z = Z*(d2 + e2*Z + f2*Z*Z), |
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| 109 | p3Z = Z*(d3 + e3*Z + f3*Z*Z), p4Z = Z*(d4 + e4*Z + f4*Z*Z); |
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| 110 | |
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| 111 | G4double T0 = 15.0*keV; |
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| 112 | if (Z < 1.5) { T0 = 40.0*keV; } |
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| 113 | |
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| 114 | G4double X = max(GammaEnergy, T0) / electron_mass_c2; |
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| 115 | CrossSection = p1Z*std::log(1.+2.*X)/X |
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| 116 | + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X); |
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| 117 | |
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| 118 | // modification for low energy. (special case for Hydrogen) |
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| 119 | if (GammaEnergy < T0) { |
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| 120 | G4double dT0 = keV; |
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| 121 | X = (T0+dT0) / electron_mass_c2 ; |
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| 122 | G4double sigma = p1Z*log(1.+2*X)/X |
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| 123 | + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X); |
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| 124 | G4double c1 = -T0*(sigma-CrossSection)/(CrossSection*dT0); |
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| 125 | G4double c2 = 0.150; |
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| 126 | if (Z > 1.5) { c2 = 0.375-0.0556*log(Z); } |
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| 127 | G4double y = log(GammaEnergy/T0); |
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| 128 | CrossSection *= exp(-y*(c1+c2*y)); |
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| 129 | } |
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| 130 | // G4cout << "e= " << GammaEnergy << " Z= " << Z |
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| 131 | // << " cross= " << CrossSection << G4endl; |
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| 132 | return CrossSection; |
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| 133 | } |
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| 134 | |
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| 135 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 136 | |
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| 137 | void G4KleinNishinaModel::SampleSecondaries( |
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| 138 | std::vector<G4DynamicParticle*>* fvect, |
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| 139 | const G4MaterialCutsCouple* couple, |
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| 140 | const G4DynamicParticle* aDynamicGamma, |
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| 141 | G4double, |
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| 142 | G4double) |
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| 143 | { |
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| 144 | G4double energy = aDynamicGamma->GetKineticEnergy(); |
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| 145 | G4ThreeVector direction = aDynamicGamma->GetMomentumDirection(); |
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| 146 | |
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| 147 | // select atom |
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| 148 | const G4Element* elm = SelectRandomAtom(couple, theGamma, energy); |
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| 149 | |
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| 150 | // select shell first |
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| 151 | G4int Z = (G4int)elm->GetZ(); |
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| 152 | G4int nShells = elm->GetNbOfAtomicShells(); |
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| 153 | if(nShells > (G4int)fProbabilities.size()) { fProbabilities.resize(nShells); } |
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| 154 | G4double totprob = 0.0; |
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| 155 | G4int i = 0; |
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| 156 | for(; i<nShells; ++i) { |
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| 157 | G4double prob = 0.0; |
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| 158 | if(energy > elm->GetAtomicShell(i)) { |
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| 159 | prob = (G4double)elm->GetNbOfShellElectrons(i); |
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| 160 | } |
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| 161 | totprob += prob; |
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| 162 | fProbabilities[i] = totprob; |
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| 163 | } |
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| 164 | if(totprob == 0.0) { return; } |
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| 165 | |
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| 166 | G4LorentzVector lv1, lv2, lv3; |
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| 167 | G4LorentzVector lv0(energy*direction.x(),energy*direction.y(), |
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| 168 | energy*direction.z(),energy); |
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| 169 | G4double eKinEnergy = 0.0; |
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| 170 | G4double gamEnergy1 = 0.0; |
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| 171 | |
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| 172 | // Loop on sampling |
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| 173 | do { |
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| 174 | G4double xprob = totprob*G4UniformRand(); |
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| 175 | |
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| 176 | for(i=0; i<nShells; ++i) { if(xprob <= fProbabilities[i]) {break;} } |
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| 177 | if( i == nShells ) { return; } |
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| 178 | |
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| 179 | G4double bindingEnergy = elm->GetAtomicShell(i); |
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| 180 | G4double tkin = bindingEnergy*0.5; |
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| 181 | G4double eEnergy = tkin + electron_mass_c2; |
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| 182 | G4double eTotMomentum = sqrt(tkin*(tkin + electron_mass_c2*2)); |
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| 183 | G4ThreeVector eDir = G4RandomDirection(); |
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| 184 | lv1 = lv0; |
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| 185 | lv2.set(eTotMomentum*eDir.x(),eTotMomentum*eDir.y(), |
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| 186 | eTotMomentum*eDir.z(),eEnergy); |
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| 187 | G4ThreeVector bst = lv2.boostVector(); |
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| 188 | lv1.boost(-bst); |
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| 189 | |
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| 190 | // In the rest frame of an electron |
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| 191 | // The scattered gamma energy is sampled according to Klein - Nishina formula. |
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| 192 | // The random number techniques of Butcher & Messel are used |
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| 193 | // (Nuc Phys 20(1960),15). |
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| 194 | |
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| 195 | G4double gamEnergy0 = lv1.e(); |
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| 196 | G4double E0_m = gamEnergy0 / electron_mass_c2 ; |
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| 197 | |
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| 198 | G4ThreeVector gamDirection0 = (lv1.vect()).unit(); |
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| 199 | |
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| 200 | // |
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| 201 | // sample the energy rate of the scattered gamma |
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| 202 | // |
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| 203 | |
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| 204 | G4double epsilon, epsilonsq, onecost, sint2, greject ; |
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| 205 | |
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| 206 | G4double epsilon0 = 1./(1. + 2.*E0_m); |
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| 207 | G4double epsilon0sq = epsilon0*epsilon0; |
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| 208 | G4double alpha1 = - log(epsilon0); |
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| 209 | G4double alpha2 = 0.5*(1.- epsilon0sq); |
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| 210 | |
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| 211 | do { |
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| 212 | if ( alpha1/(alpha1+alpha2) > G4UniformRand() ) { |
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| 213 | epsilon = exp(-alpha1*G4UniformRand()); // epsilon0**r |
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| 214 | epsilonsq = epsilon*epsilon; |
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| 215 | |
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| 216 | } else { |
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| 217 | epsilonsq = epsilon0sq + (1.- epsilon0sq)*G4UniformRand(); |
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| 218 | epsilon = sqrt(epsilonsq); |
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| 219 | }; |
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| 220 | |
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| 221 | onecost = (1.- epsilon)/(epsilon*E0_m); |
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| 222 | sint2 = onecost*(2.-onecost); |
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| 223 | greject = 1. - epsilon*sint2/(1.+ epsilonsq); |
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| 224 | |
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| 225 | } while (greject < G4UniformRand()); |
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| 226 | |
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| 227 | // |
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| 228 | // scattered gamma angles. ( Z - axis along the parent gamma) |
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| 229 | // |
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| 230 | |
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| 231 | G4double cosTeta = 1. - onecost; |
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| 232 | G4double sinTeta = sqrt (sint2); |
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| 233 | G4double Phi = twopi * G4UniformRand(); |
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| 234 | G4double dirx = sinTeta*cos(Phi), diry = sinTeta*sin(Phi), dirz = cosTeta; |
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| 235 | |
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| 236 | // |
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| 237 | // update G4VParticleChange for the scattered gamma |
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| 238 | // |
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| 239 | |
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| 240 | G4ThreeVector gamDirection1 ( dirx,diry,dirz ); |
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| 241 | gamDirection1.rotateUz(gamDirection0); |
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| 242 | gamEnergy1 = epsilon*gamEnergy0; |
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| 243 | |
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| 244 | // before scattering |
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| 245 | lv2.set(0.0,0.0,0.0,electron_mass_c2); |
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| 246 | lv2 += lv1; |
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| 247 | |
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| 248 | // after scattering |
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| 249 | lv1.set(gamEnergy1*gamDirection1.x(),gamEnergy1*gamDirection1.y(), |
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| 250 | gamEnergy1*gamDirection1.z(),gamEnergy1); |
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| 251 | lv2 -= lv1; |
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| 252 | lv2.boost(bst); |
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| 253 | lv1.boost(bst); |
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| 254 | eKinEnergy = lv2.e() - electron_mass_c2 - bindingEnergy; |
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| 255 | } while ( eKinEnergy < 0.0 ); |
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| 256 | |
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| 257 | // gamma kinematics |
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| 258 | gamEnergy1 = lv1.e(); |
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| 259 | if(gamEnergy1 > lowestGammaEnergy) { |
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| 260 | fParticleChange->SetProposedKineticEnergy(gamEnergy1); |
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| 261 | fParticleChange->ProposeMomentumDirection((lv1.vect()).unit()); |
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| 262 | } else { |
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| 263 | fParticleChange->ProposeTrackStatus(fStopAndKill); |
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| 264 | fParticleChange->ProposeLocalEnergyDeposit(gamEnergy1); |
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| 265 | } |
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| 266 | |
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| 267 | // |
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| 268 | // kinematic of the scattered electron |
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| 269 | // |
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| 270 | if(eKinEnergy > DBL_MIN) { |
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| 271 | G4ThreeVector eDirection = (lv2.vect()).unit(); |
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| 272 | G4DynamicParticle* dp = new G4DynamicParticle(theElectron,eDirection,eKinEnergy); |
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| 273 | fvect->push_back(dp); |
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| 274 | } |
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| 275 | // sample deexcitation |
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| 276 | // |
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| 277 | if(fAtomDeexcitation) { |
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| 278 | G4AtomicShellEnumerator as = G4AtomicShellEnumerator(i); |
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| 279 | const G4AtomicShell* shell = fAtomDeexcitation->GetAtomicShell(Z, as); |
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| 280 | fAtomDeexcitation->GenerateParticles(fvect, shell, Z, couple->GetIndex()); |
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| 281 | } |
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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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