| 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: G4CrossSectionElasticScreenedRutherfordLE.cc,v 1.2 2008/07/14 20:47:34 sincerti Exp $
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| 27 | // GEANT4 tag $Name: geant4-09-02 $
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| 28 |
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| 29 | #include "G4CrossSectionElasticScreenedRutherfordLE.hh"
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| 30 |
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| 31 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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| 32 |
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| 33 | G4CrossSectionElasticScreenedRutherfordLE::G4CrossSectionElasticScreenedRutherfordLE()
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| 34 | {
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| 35 | lowEnergyLimit = 0 * eV;
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| 36 | highEnergyLimit = 200 * eV;
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| 37 | }
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| 38 |
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| 39 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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| 40 |
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| 41 | G4CrossSectionElasticScreenedRutherfordLE::~G4CrossSectionElasticScreenedRutherfordLE()
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| 42 | {}
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| 43 |
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| 44 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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| 45 |
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| 46 | G4double G4CrossSectionElasticScreenedRutherfordLE::CrossSection(const G4Track& track)
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| 47 | {
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| 48 | const G4DynamicParticle* particle = track.GetDynamicParticle();
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| 49 | G4double k = particle->GetKineticEnergy();
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| 50 |
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| 51 | G4double screenedCrossSection = 0.;
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| 52 |
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| 53 | if (k > lowEnergyLimit && k <= highEnergyLimit)
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| 54 | {
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| 55 | G4double z = 10.;
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| 56 | G4double n = ScreeningFactor(k,z);
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| 57 | G4double crossSection = RutherfordCrossSection(k, z);
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| 58 | screenedCrossSection = pi * crossSection / (n * (n + 1.));
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| 59 | }
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| 60 |
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| 61 | return screenedCrossSection;
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| 62 | }
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| 63 |
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| 64 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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| 65 |
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| 66 | G4double G4CrossSectionElasticScreenedRutherfordLE::RutherfordCrossSection(G4double k, G4double z)
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| 67 | {
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| 68 | //
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| 69 | // e^4 / K + m_e c^2 \^2
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| 70 | // sigma_Ruth(K) = Z (Z+1) -------------------- | --------------------- |
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| 71 | // (4 pi epsilon_0)^2 \ K * (K + 2 m_e c^2) /
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| 72 | //
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| 73 | // Where K is the electron non-relativistic kinetic energy
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| 74 | //
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| 75 | // NIM 155, pp. 145-156, 1978
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| 76 |
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| 77 | G4double length =(e_squared * (k + electron_mass_c2)) / (4 * pi *epsilon0 * k * ( k + 2 * electron_mass_c2));
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| 78 | G4double cross = z * ( z + 1) * length * length;
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| 79 |
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| 80 | return cross;
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| 81 | }
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| 82 |
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| 83 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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| 84 |
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| 85 | G4double G4CrossSectionElasticScreenedRutherfordLE::ScreeningFactor(G4double k, G4double z)
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| 86 | {
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| 87 | //
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| 88 | // alpha_1 + beta_1 ln(K/eV) constK Z^(2/3)
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| 89 | // n(T) = -------------------------- -----------------
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| 90 | // K/(m_e c^2) 2 + K/(m_e c^2)
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| 91 | //
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| 92 | // Where K is the electron non-relativistic kinetic energy
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| 93 | //
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| 94 | // n(T) > 0 for T < ~ 400 MeV
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| 95 | //
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| 96 | // NIM 155, pp. 145-156, 1978
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| 97 | // Formulae (2) and (5)
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| 98 |
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| 99 | const G4double alpha_1(1.64);
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| 100 | const G4double beta_1(-0.0825);
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| 101 | const G4double constK(1.7E-5);
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| 102 |
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| 103 | G4double numerator = (alpha_1 + beta_1 * std::log(k/eV)) * constK * std::pow(z, 2./3.);
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| 104 |
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| 105 | k /= electron_mass_c2;
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| 106 |
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| 107 | G4double denominator = k * (2 + k);
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| 108 |
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| 109 | G4double value = 0.;
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| 110 | if (denominator > 0.) value = numerator / denominator;
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| 111 |
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| 112 | return value;
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| 113 | }
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