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 | // |
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27 | // $Id: G4CrossSectionElasticScreenedRutherford.cc,v 1.1 2007/10/12 23:11:41 pia Exp $ |
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28 | // GEANT4 tag $Name: geant4-09-03-cand-01 $ |
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29 | // |
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30 | // Contact Author: Maria Grazia Pia (Maria.Grazia.Pia@cern.ch) |
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31 | // |
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32 | // Reference: TNS Geant4-DNA paper |
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33 | // Reference for implementation model: NIM. 155, pp. 145-156, 1978 |
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34 | |
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35 | // History: |
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36 | // ----------- |
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37 | // Date Name Modification |
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38 | // 28 Apr 2007 M.G. Pia Created in compliance with design described in TNS paper |
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39 | // |
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40 | // ------------------------------------------------------------------- |
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41 | |
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42 | // Class description: |
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43 | // Geant4-DNA Cross total cross section for electron elastic scattering in water |
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44 | // Reference: TNS Geant4-DNA paper |
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45 | // S. Chauvie et al., Geant4 physics processes for microdosimetry simulation: |
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46 | // design foundation and implementation of the first set of models, |
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47 | // IEEE Trans. Nucl. Sci., vol. 54, no. 6, Dec. 2007. |
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48 | // Further documentation available from http://www.ge.infn.it/geant4/dna |
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49 | |
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50 | // ------------------------------------------------------------------- |
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51 | |
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52 | |
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53 | #include "G4CrossSectionElasticScreenedRutherford.hh" |
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54 | #include "G4Track.hh" |
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55 | #include "G4DynamicParticle.hh" |
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56 | #include "G4ParticleDefinition.hh" |
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57 | #include "G4Electron.hh" |
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58 | |
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59 | |
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60 | G4CrossSectionElasticScreenedRutherford::G4CrossSectionElasticScreenedRutherford() |
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61 | { |
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62 | |
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63 | name = "CrossSectionElasticScreenedRutherford"; |
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64 | lowEnergyLimit = 7. * eV; |
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65 | highEnergyLimit = 10 * MeV; |
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66 | |
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67 | // if (verboseLevel > 0) |
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68 | // { |
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69 | // G4cout << name << " is created " << G4endl |
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70 | // << "Energy range: " |
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71 | // << lowEnergyLimit / keV << " keV - " |
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72 | // << highEnergyLimit / GeV << " GeV" |
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73 | // << G4endl; |
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74 | // } |
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75 | } |
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76 | |
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77 | |
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78 | G4CrossSectionElasticScreenedRutherford::~G4CrossSectionElasticScreenedRutherford() |
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79 | { } |
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80 | |
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81 | |
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82 | G4double G4CrossSectionElasticScreenedRutherford::CrossSection(const G4Track& track) |
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83 | { |
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84 | const G4DynamicParticle* particle = track.GetDynamicParticle(); |
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85 | G4double k = particle->GetKineticEnergy(); |
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86 | |
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87 | // Cross section = 0 outside the energy validity limits set in the constructor |
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88 | // ---- MGP ---- Better handling of these limits to be set in a following design iteration |
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89 | |
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90 | G4double screenedCrossSection = 0.; |
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91 | |
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92 | if (k > lowEnergyLimit && k < highEnergyLimit) |
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93 | { |
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94 | // G4Material* material = track.GetMaterial(); |
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95 | |
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96 | // Assume that the material is water; proper algorithm to calculate z correctly for any material to be inserted here |
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97 | // For H20 Z = 10 (total number of electrons) |
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98 | G4double z = 10.; |
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99 | |
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100 | G4double n = ScreeningFactor(k,z); |
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101 | G4double crossSection = RutherfordCrossSection(k, z); |
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102 | screenedCrossSection = pi * crossSection / (n * (n + 1.)); |
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103 | } |
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104 | |
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105 | return screenedCrossSection; |
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106 | } |
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107 | |
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108 | G4double G4CrossSectionElasticScreenedRutherford::RutherfordCrossSection(G4double k, G4double z) |
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109 | { |
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110 | // |
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111 | // e^4 / K + m_e c^2 \^2 |
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112 | // sigma_Ruth(K) = Z (Z+1) -------------------- | --------------------- | |
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113 | // (4 pi epsilon_0)^2 \ K * (K + 2 m_e c^2) / |
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114 | // |
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115 | // Where K is the electron non-relativistic kinetic energy |
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116 | // |
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117 | // NIM 155, pp. 145-156, 1978 |
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118 | |
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119 | G4double length =(e_squared * (k + electron_mass_c2)) / (4 * pi *epsilon0 * k * ( k + 2 * electron_mass_c2)); |
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120 | G4double cross = z * ( z + 1) * length * length; |
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121 | |
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122 | return cross; |
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123 | } |
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124 | |
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125 | //G4bool G4CrossSectionElasticScreenedRutherford::IsApplicable(const G4ParticleDefinition& particle) |
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126 | //{ |
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127 | // return ( &particle == G4Electron::Electron() ); |
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128 | //} |
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129 | |
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130 | |
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131 | G4double G4CrossSectionElasticScreenedRutherford::ScreeningFactor(G4double k, G4double z) |
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132 | { |
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133 | // |
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134 | // alpha_1 + beta_1 ln(K/eV) constK Z^(2/3) |
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135 | // n(T) = -------------------------- ----------------- |
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136 | // K/(m_e c^2) 2 + K/(m_e c^2) |
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137 | // |
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138 | // Where K is the electron non-relativistic kinetic energy |
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139 | // |
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140 | // n(T) > 0 for T < ~ 400 MeV |
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141 | // |
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142 | // NIM 155, pp. 145-156, 1978 |
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143 | // Formulae (2) and (5) |
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144 | |
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145 | const G4double alpha_1(1.64); |
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146 | const G4double beta_1(-0.0825); |
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147 | const G4double constK(1.7E-5); |
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148 | |
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149 | G4double numerator = (alpha_1 + beta_1 * std::log(k/eV)) * constK * std::pow(z, 2./3.); |
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150 | |
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151 | k /= electron_mass_c2; |
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152 | |
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153 | G4double denominator = k * (2 + k); |
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154 | |
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155 | G4double value = 0.; |
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156 | if (denominator > 0.) value = numerator / denominator; |
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157 | |
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158 | return value; |
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159 | |
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160 | } |
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161 | |
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