[807] | 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: MyKleinNishinaCompton.cc,v 1.5 2007/10/01 15:19:57 maire Exp $ |
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| 27 | // GEANT4 tag $Name: $ |
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| 28 | // |
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| 29 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 30 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 31 | |
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| 32 | #include "MyKleinNishinaCompton.hh" |
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| 33 | #include "DetectorConstruction.hh" |
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| 34 | |
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| 35 | #include "G4Electron.hh" |
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| 36 | #include "G4Gamma.hh" |
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| 37 | #include "Randomize.hh" |
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| 38 | #include "G4DataVector.hh" |
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| 39 | #include "G4ParticleChangeForGamma.hh" |
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| 40 | |
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| 41 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 42 | |
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| 43 | using namespace std; |
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| 44 | |
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| 45 | MyKleinNishinaCompton::MyKleinNishinaCompton(DetectorConstruction* det, |
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| 46 | const G4ParticleDefinition*, |
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| 47 | const G4String& nam) |
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| 48 | :G4KleinNishinaCompton(0,nam), detector(det) |
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| 49 | { |
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| 50 | CrossSectionFactor = 1.; |
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| 51 | } |
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| 52 | |
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| 53 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 54 | |
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| 55 | MyKleinNishinaCompton::~MyKleinNishinaCompton() |
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| 56 | {} |
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| 57 | |
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| 58 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 59 | |
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| 60 | G4double MyKleinNishinaCompton::CrossSectionPerVolume( |
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| 61 | const G4Material* mat, |
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| 62 | const G4ParticleDefinition* part, |
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| 63 | G4double GammaEnergy, |
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| 64 | G4double, G4double) |
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| 65 | { |
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| 66 | G4double CrossSection = |
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| 67 | G4VEmModel::CrossSectionPerVolume(mat,part,GammaEnergy); |
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| 68 | |
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| 69 | return CrossSection*CrossSectionFactor; |
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| 70 | } |
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| 71 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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| 72 | |
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| 73 | void MyKleinNishinaCompton::SampleSecondaries( |
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| 74 | std::vector<G4DynamicParticle*>* fvect, |
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| 75 | const G4MaterialCutsCouple*, |
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| 76 | const G4DynamicParticle* aDynamicGamma, |
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| 77 | G4double, |
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| 78 | G4double) |
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| 79 | { |
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| 80 | // The scattered gamma energy is sampled according to Klein - Nishina formula. |
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| 81 | // The random number techniques of Butcher & Messel are used |
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| 82 | // (Nuc Phys 20(1960),15). |
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| 83 | // Note : Effects due to binding of atomic electrons are negliged. |
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| 84 | |
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| 85 | G4double gamEnergy0 = aDynamicGamma->GetKineticEnergy(); |
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| 86 | G4double E0_m = gamEnergy0 / electron_mass_c2 ; |
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| 87 | |
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| 88 | G4ThreeVector gamDirection0 = aDynamicGamma->GetMomentumDirection(); |
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| 89 | |
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| 90 | // |
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| 91 | // sample the energy rate of the scattered gamma |
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| 92 | // |
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| 93 | |
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| 94 | G4double epsilon, epsilonsq, onecost, sint2, greject ; |
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| 95 | |
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| 96 | G4double epsilon0 = 1./(1. + 2.*E0_m); |
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| 97 | G4double epsilon0sq = epsilon0*epsilon0; |
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| 98 | G4double alpha1 = - log(epsilon0); |
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| 99 | G4double alpha2 = 0.5*(1.- epsilon0sq); |
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| 100 | |
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| 101 | do { |
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| 102 | if ( alpha1/(alpha1+alpha2) > G4UniformRand() ) { |
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| 103 | epsilon = exp(-alpha1*G4UniformRand()); // epsilon0**r |
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| 104 | epsilonsq = epsilon*epsilon; |
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| 105 | |
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| 106 | } else { |
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| 107 | epsilonsq = epsilon0sq + (1.- epsilon0sq)*G4UniformRand(); |
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| 108 | epsilon = sqrt(epsilonsq); |
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| 109 | }; |
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| 110 | |
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| 111 | onecost = (1.- epsilon)/(epsilon*E0_m); |
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| 112 | sint2 = onecost*(2.-onecost); |
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| 113 | greject = 1. - epsilon*sint2/(1.+ epsilonsq); |
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| 114 | |
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| 115 | } while (greject < G4UniformRand()); |
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| 116 | |
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| 117 | // |
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| 118 | // scattered gamma angles. ( Z - axis along the parent gamma) |
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| 119 | // |
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| 120 | |
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| 121 | G4double cosTeta = 1. - onecost; |
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| 122 | G4double sinTeta = sqrt (sint2); |
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| 123 | G4double Phi = twopi * G4UniformRand(); |
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| 124 | G4double dirx = sinTeta*cos(Phi), diry = sinTeta*sin(Phi), dirz = cosTeta; |
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| 125 | |
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| 126 | // |
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| 127 | // update G4VParticleChange for the scattered gamma |
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| 128 | // |
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| 129 | // beam regeneration trick : restore incident beam |
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| 130 | |
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| 131 | G4ThreeVector gamDirection1 ( dirx,diry,dirz ); |
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| 132 | gamDirection1.rotateUz(gamDirection0); |
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| 133 | G4double gamEnergy1 = epsilon*gamEnergy0; |
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| 134 | fParticleChange->SetProposedKineticEnergy(gamEnergy0); |
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| 135 | fParticleChange->ProposeMomentumDirection(gamDirection0); |
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| 136 | |
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| 137 | // |
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| 138 | // kinematic of the scattered electron |
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| 139 | // |
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| 140 | |
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| 141 | G4double eKinEnergy = gamEnergy0 - gamEnergy1; |
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| 142 | |
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| 143 | if(eKinEnergy > DBL_MIN) { |
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| 144 | G4ThreeVector eDirection |
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| 145 | = gamEnergy0*gamDirection0 - gamEnergy1*gamDirection1; |
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| 146 | eDirection = eDirection.unit(); |
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| 147 | |
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| 148 | // create G4DynamicParticle object for the electron. |
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| 149 | G4DynamicParticle* dp |
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| 150 | = new G4DynamicParticle(theElectron,eDirection,eKinEnergy); |
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| 151 | fvect->push_back(dp); |
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| 152 | } |
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| 153 | } |
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| 154 | |
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| 155 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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| 156 | |
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| 157 | |
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