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: G4ScreenedNuclearRecoil.cc,v 1.5 2008/01/14 12:11:39 vnivanch Exp $ |
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28 | // GEANT4 tag $Name: $ |
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29 | // |
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30 | // |
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31 | // Class Description |
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32 | // Process for screened electromagnetic nuclear elastic scattering; |
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33 | // Physics comes from: |
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34 | // Marcus H. Mendenhall and Robert A. Weller, |
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35 | // "Algorithms for the rapid computation of classical cross |
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36 | // sections for screened Coulomb collisions " |
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37 | // Nuclear Instruments and Methods in Physics Research B58 (1991) 11-17 |
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38 | // The only input required is a screening function phi(r/a) which is the ratio |
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39 | // of the actual interatomic potential for two atoms with atomic numbers Z1 and Z2, |
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40 | // to the unscreened potential Z1*Z2*e^2/r where e^2 is elm_coupling in Geant4 units |
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41 | // |
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42 | // First version, April 2004, Marcus H. Mendenhall, Vanderbilt University |
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43 | // |
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44 | // 5 May, 2004, Marcus Mendenhall |
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45 | // Added an option for enhancing hard collisions statistically, to allow |
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46 | // backscattering calculations to be carried out with much improved event rates, |
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47 | // without distorting the multiple-scattering broadening too much. |
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48 | // the method SetCrossSectionHardening(G4double fraction, G4double HardeningFactor) |
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49 | // sets what fraction of the events will be randomly hardened, |
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50 | // and the factor by which the impact area is reduced for such selected events. |
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51 | // |
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52 | // 21 November, 2004, Marcus Mendenhall |
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53 | // added static_nucleus to IsApplicable |
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54 | // |
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55 | // 7 December, 2004, Marcus Mendenhall |
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56 | // changed mean free path of stopping particle from 0.0 to 1.0*nanometer |
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57 | // to avoid new verbose warning about 0 MFP in 4.6.2p02 |
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58 | // |
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59 | // 17 December, 2004, Marcus Mendenhall |
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60 | // added code to permit screening out overly close collisions which are |
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61 | // expected to be hadronic, not Coulombic |
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62 | // |
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63 | // 19 December, 2004, Marcus Mendenhall |
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64 | // massive rewrite to add modular physics stages and plug-in cross section table |
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65 | // computation. This allows one to select (e.g.) between the normal external python |
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66 | // process and an embedded python interpreter (which is much faster) for generating |
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67 | // the tables. |
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68 | // It also allows one to switch between sub-sampled scattering (event biasing) and |
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69 | // normal scattering, and between non-relativistic kinematics and relativistic |
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70 | // kinematic approximations, without having a class for every combination. Further, one can |
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71 | // add extra stages to the scattering, which can implement various book-keeping processes. |
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72 | // |
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73 | // January 2007, Marcus Mendenhall |
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74 | // Reorganized heavily for inclusion in Geant4 Core. All modules merged into |
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75 | // one source and header, all historic code removed. |
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76 | // |
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77 | // Class Description - End |
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78 | |
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79 | |
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80 | #include <stdio.h> |
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81 | |
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82 | #include "globals.hh" |
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83 | |
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84 | #include "G4ScreenedNuclearRecoil.hh" |
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85 | |
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86 | #include "G4ParticleTypes.hh" |
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87 | #include "G4ParticleTable.hh" |
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88 | #include "G4VParticleChange.hh" |
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89 | #include "G4ParticleChange.hh" |
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90 | #include "G4DataVector.hh" |
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91 | #include "G4Track.hh" |
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92 | #include "G4Step.hh" |
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93 | |
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94 | #include "G4Material.hh" |
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95 | #include "G4Element.hh" |
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96 | #include "G4Isotope.hh" |
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97 | #include "G4MaterialCutsCouple.hh" |
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98 | #include "G4ElementVector.hh" |
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99 | #include "G4IsotopeVector.hh" |
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100 | |
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101 | #include "G4RangeTest.hh" |
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102 | #include "G4ParticleDefinition.hh" |
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103 | #include "G4DynamicParticle.hh" |
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104 | #include "G4ProcessManager.hh" |
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105 | #include "G4StableIsotopes.hh" |
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106 | |
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107 | #include "Randomize.hh" |
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108 | |
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109 | #include "CLHEP/Units/PhysicalConstants.h" |
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110 | |
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111 | #include <iostream> |
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112 | #include <iomanip> |
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113 | |
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114 | G4ScreenedCoulombCrossSection::~G4ScreenedCoulombCrossSection() |
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115 | { |
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116 | ScreeningMap::iterator tables=screeningData.begin(); |
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117 | for (;tables != screeningData.end(); tables++) { |
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118 | delete (*tables).second.EMphiData; |
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119 | } |
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120 | screeningData.clear(); |
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121 | |
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122 | std::map<G4int, c2_function<G4double> *>::iterator mfpit=MFPTables.begin(); |
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123 | for (;mfpit != MFPTables.end(); mfpit++) { |
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124 | delete (*mfpit).second; |
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125 | } |
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126 | MFPTables.clear(); |
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127 | |
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128 | } |
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129 | |
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130 | const G4double G4ScreenedCoulombCrossSection::massmap[nMassMapElements+1]={ |
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131 | 0, 1.007940, 4.002602, 6.941000, 9.012182, 10.811000, 12.010700, |
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132 | 14.006700, 15.999400, 18.998403, 20.179700, 22.989770, 24.305000, 26.981538, 28.085500, |
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133 | 30.973761, 32.065000, 35.453000, 39.948000, 39.098300, 40.078000, 44.955910, 47.867000, |
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134 | 50.941500, 51.996100, 54.938049, 55.845000, 58.933200, 58.693400, 63.546000, 65.409000, |
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135 | 69.723000, 72.640000, 74.921600, 78.960000, 79.904000, 83.798000, 85.467800, 87.620000, |
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136 | 88.905850, 91.224000, 92.906380, 95.940000, 98.000000, 101.070000, 102.905500, 106.420000, |
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137 | 107.868200, 112.411000, 114.818000, 118.710000, 121.760000, 127.600000, 126.904470, 131.293000, |
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138 | 132.905450, 137.327000, 138.905500, 140.116000, 140.907650, 144.240000, 145.000000, 150.360000, |
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139 | 151.964000, 157.250000, 158.925340, 162.500000, 164.930320, 167.259000, 168.934210, 173.040000, |
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140 | 174.967000, 178.490000, 180.947900, 183.840000, 186.207000, 190.230000, 192.217000, 195.078000, |
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141 | 196.966550, 200.590000, 204.383300, 207.200000, 208.980380, 209.000000, 210.000000, 222.000000, |
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142 | 223.000000, 226.000000, 227.000000, 232.038100, 231.035880, 238.028910, 237.000000, 244.000000, |
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143 | 243.000000, 247.000000, 247.000000, 251.000000, 252.000000, 257.000000, 258.000000, 259.000000, |
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144 | 262.000000, 261.000000, 262.000000, 266.000000, 264.000000, 277.000000, 268.000000, 281.000000, |
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145 | 272.000000, 285.000000, 282.500000, 289.000000, 287.500000, 292.000000}; |
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146 | |
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147 | G4ParticleDefinition* G4ScreenedCoulombCrossSection::SelectRandomUnweightedTarget(const G4MaterialCutsCouple* couple) |
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148 | { |
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149 | // Select randomly an element within the material, according to number density only |
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150 | const G4Material* material = couple->GetMaterial(); |
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151 | G4int nMatElements = material->GetNumberOfElements(); |
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152 | const G4ElementVector* elementVector = material->GetElementVector(); |
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153 | const G4Element *element=0; |
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154 | G4ParticleDefinition*target=0; |
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155 | |
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156 | // Special case: the material consists of one element |
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157 | if (nMatElements == 1) |
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158 | { |
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159 | element= (*elementVector)[0]; |
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160 | } |
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161 | else |
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162 | { |
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163 | // Composite material |
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164 | G4double random = G4UniformRand() * material->GetTotNbOfAtomsPerVolume(); |
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165 | G4double nsum=0.0; |
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166 | const G4double *atomDensities=material->GetVecNbOfAtomsPerVolume(); |
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167 | |
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168 | for (G4int k=0 ; k < nMatElements ; k++ ) |
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169 | { |
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170 | nsum+=atomDensities[k]; |
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171 | element= (*elementVector)[k]; |
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172 | if (nsum >= random) break; |
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173 | } |
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174 | } |
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175 | |
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176 | G4int N=0; |
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177 | G4int Z=(G4int)std::floor(element->GetZ()+0.5); |
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178 | |
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179 | G4int nIsotopes=element->GetNumberOfIsotopes(); |
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180 | if(!nIsotopes) { |
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181 | if(Z<=92) { |
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182 | // we have no detailed material isotopic info available, |
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183 | // so use G4StableIsotopes table up to Z=92 |
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184 | static G4StableIsotopes theIso; // get a stable isotope table for default results |
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185 | nIsotopes=theIso.GetNumberOfIsotopes(Z); |
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186 | G4double random = 100.0*G4UniformRand(); // values are expressed as percent, sum is 100 |
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187 | G4int tablestart=theIso.GetFirstIsotope(Z); |
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188 | G4double asum=0.0; |
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189 | for(G4int i=0; i<nIsotopes; i++) { |
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190 | asum+=theIso.GetAbundance(i+tablestart); |
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191 | N=theIso.GetIsotopeNucleonCount(i+tablestart); |
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192 | if(asum >= random) break; |
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193 | } |
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194 | } else { |
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195 | // too heavy for stable isotope table, just use mean mass |
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196 | N=(G4int)std::floor(element->GetN()+0.5); |
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197 | } |
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198 | } else { |
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199 | G4int i; |
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200 | const G4IsotopeVector *isoV=element->GetIsotopeVector(); |
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201 | G4double random = G4UniformRand(); |
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202 | G4double *abundance=element->GetRelativeAbundanceVector(); |
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203 | G4double asum=0.0; |
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204 | for(i=0; i<nIsotopes; i++) { |
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205 | asum+=abundance[i]; |
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206 | N=(*isoV)[i]->GetN(); |
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207 | if(asum >= random) break; |
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208 | } |
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209 | } |
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210 | |
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211 | // get the official definition of this nucleus, to get the correct value of A |
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212 | // note that GetIon is very slow, so we will cache ones we have already found ourselves. |
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213 | ParticleCache::iterator p=targetMap.find(Z*1000+N); |
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214 | if (p != targetMap.end()) { |
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215 | target=(*p).second; |
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216 | } else{ |
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217 | target=G4ParticleTable::GetParticleTable()->GetIon(Z, N, 0.0); |
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218 | targetMap[Z*1000+N]=target; |
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219 | } |
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220 | return target; |
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221 | } |
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222 | |
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223 | void G4ScreenedCoulombCrossSection::BuildMFPTables() |
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224 | { |
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225 | const G4int nmfpvals=200; |
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226 | |
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227 | std::vector<G4double> evals(nmfpvals), mfpvals(nmfpvals); |
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228 | |
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229 | // sum up inverse MFPs per element for each material |
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230 | const G4MaterialTable* materialTable = G4Material::GetMaterialTable(); |
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231 | if (materialTable == 0) |
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232 | G4Exception("G4ScreenedCoulombCrossSection::BuildMFPTables - no MaterialTable found)"); |
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233 | |
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234 | G4int nMaterials = G4Material::GetNumberOfMaterials(); |
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235 | |
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236 | for (G4int matidx=0; matidx < nMaterials; matidx++) { |
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237 | |
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238 | const G4Material* material= (*materialTable)[matidx]; |
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239 | const G4ElementVector &elementVector = *(material->GetElementVector()); |
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240 | const G4int nMatElements = material->GetNumberOfElements(); |
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241 | |
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242 | const G4Element *element=0; |
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243 | const G4double *atomDensities=material->GetVecNbOfAtomsPerVolume(); |
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244 | |
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245 | G4double emin=0, emax=0; // find innermost range of cross section functions |
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246 | for (G4int kel=0 ; kel < nMatElements ; kel++ ) |
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247 | { |
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248 | element=elementVector[kel]; |
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249 | G4int Z=(G4int)std::floor(element->GetZ()+0.5); |
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250 | c2_function<G4double> &ifunc=*sigmaMap[Z]; |
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251 | if(!kel || ifunc.xmin() > emin) emin=ifunc.xmin(); |
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252 | if(!kel || ifunc.xmax() < emax) emax=ifunc.xmax(); |
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253 | } |
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254 | |
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255 | G4double logint=std::log(emax/emin) / (nmfpvals-1) ; // logarithmic increment for tables |
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256 | |
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257 | // compute energy scale for interpolator. Force exact values at both ends to avoid range errors |
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258 | for (G4int i=1; i<nmfpvals-1; i++) evals[i]=emin*std::exp(logint*i); |
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259 | evals.front()=emin; |
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260 | evals.back()=emax; |
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261 | |
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262 | // zero out the inverse mfp sums to start |
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263 | for (G4int eidx=0; eidx < nmfpvals; eidx++) mfpvals[eidx] = 0.0; |
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264 | |
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265 | // sum inverse mfp for each element in this material and for each energy |
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266 | for (G4int kel=0 ; kel < nMatElements ; kel++ ) |
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267 | { |
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268 | element=elementVector[kel]; |
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269 | G4int Z=(G4int)std::floor(element->GetZ()+0.5); |
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270 | c2_function<G4double> &sigma=*sigmaMap[Z]; |
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271 | G4double ndens = atomDensities[kel]; // compute atom fraction for this element in this material |
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272 | |
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273 | for (G4int eidx=0; eidx < nmfpvals; eidx++) { |
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274 | mfpvals[eidx] += ndens*sigma(evals[eidx]); |
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275 | } |
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276 | } |
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277 | |
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278 | // convert inverse mfp to regular mfp |
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279 | for (G4int eidx=0; eidx < nmfpvals; eidx++) { |
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280 | mfpvals[eidx] = 1.0/mfpvals[eidx]; |
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281 | } |
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282 | // and make a new interpolating function out of the sum |
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283 | MFPTables[matidx] = static_cast<c2_function<G4double> *>(new log_log_interpolating_function<G4double>( |
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284 | evals, mfpvals)); |
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285 | } |
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286 | |
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287 | #ifdef DEBUG |
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288 | for (G4int matidx=0; matidx < nMaterials; matidx++) { |
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289 | const G4Material* material= (*materialTable)[matidx]; |
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290 | G4cout << "***** MFP (1MeV) ***** " << material->GetName() << " " << (*MFPTables[matidx])(1.0) << G4endl; |
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291 | } |
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292 | #endif |
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293 | |
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294 | } |
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295 | |
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296 | G4ScreenedNuclearRecoil:: |
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297 | G4ScreenedNuclearRecoil(const G4String& processName, |
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298 | const G4String &ScreeningKey, |
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299 | G4bool GenerateRecoils, |
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300 | G4double RecoilCutoff, G4double PhysicsCutoff) : |
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301 | G4VDiscreteProcess(processName), |
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302 | screeningKey(ScreeningKey), |
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303 | generateRecoils(GenerateRecoils), avoidReactions(1), |
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304 | recoilCutoff(RecoilCutoff), physicsCutoff(PhysicsCutoff), |
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305 | hardeningFraction(0.0), hardeningFactor(1.0), |
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306 | externalCrossSectionConstructor(0) |
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307 | { |
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308 | highEnergyLimit=100.0*MeV; |
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309 | lowEnergyLimit=physicsCutoff; |
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310 | registerDepositedEnergy=1; // by default, don't hide NIEL |
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311 | MFPScale=1.0; |
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312 | // SetVerboseLevel(2); |
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313 | AddStage(new G4ScreenedCoulombClassicalKinematics); |
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314 | AddStage(new G4SingleScatter); |
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315 | } |
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316 | |
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317 | void G4ScreenedNuclearRecoil::ResetTables() |
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318 | { |
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319 | std::map<G4int, c2_function<G4double>*>::iterator xh=meanFreePathTables.begin(); |
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320 | for(;xh != meanFreePathTables.end(); xh++) { |
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321 | delete (*xh).second; |
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322 | } |
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323 | meanFreePathTables.clear(); |
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324 | |
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325 | std::map<G4int, G4ScreenedCoulombCrossSection*>::iterator xt=crossSectionHandlers.begin(); |
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326 | for(;xt != crossSectionHandlers.end(); xt++) { |
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327 | delete (*xt).second; |
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328 | } |
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329 | crossSectionHandlers.clear(); |
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330 | } |
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331 | |
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332 | void G4ScreenedNuclearRecoil::ClearStages() |
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333 | { |
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334 | // I don't think I like deleting the processes here... they are better abandoned |
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335 | // if the creator doesn't get rid of them |
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336 | // std::vector<G4ScreenedCollisionStage *>::iterator stage=collisionStages.begin(); |
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337 | //for(; stage != collisionStages.end(); stage++) delete (*stage); |
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338 | |
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339 | collisionStages.clear(); |
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340 | } |
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341 | |
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342 | G4ScreenedNuclearRecoil::~G4ScreenedNuclearRecoil() |
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343 | { |
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344 | ResetTables(); |
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345 | } |
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346 | |
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347 | // returns true if it appears the nuclei collided, and we are interested in checking |
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348 | G4bool G4ScreenedNuclearRecoil::CheckNuclearCollision( |
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349 | G4double A, G4double a1, G4double apsis) { |
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350 | return avoidReactions && (apsis < (1.1*(std::pow(A,1.0/3.0)+std::pow(a1,1.0/3.0)) + 1.4)*fermi); |
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351 | // nuclei are within 1.4 fm (reduced pion Compton wavelength) of each other at apsis, |
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352 | // this is hadronic, skip it |
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353 | } |
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354 | |
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355 | G4ScreenedCoulombCrossSection *G4ScreenedNuclearRecoil::GetNewCrossSectionHandler(void) { |
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356 | G4ScreenedCoulombCrossSection *xc; |
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357 | if(!externalCrossSectionConstructor) xc=new G4NativeScreenedCoulombCrossSection; |
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358 | else xc=externalCrossSectionConstructor->create(); |
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359 | xc->SetVerbosity(verboseLevel); |
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360 | return xc; |
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361 | } |
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362 | |
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363 | G4double G4ScreenedNuclearRecoil::GetMeanFreePath(const G4Track& track, |
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364 | G4double, |
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365 | G4ForceCondition*) |
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366 | { |
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367 | const G4DynamicParticle* incoming = track.GetDynamicParticle(); |
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368 | G4double energy = incoming->GetKineticEnergy(); |
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369 | G4double a1=incoming->GetDefinition()->GetPDGMass()/amu_c2; |
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370 | |
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371 | G4double meanFreePath; |
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372 | |
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373 | if (energy < lowEnergyLimit || energy < recoilCutoff) return 1.0*nanometer; /* stop slow particles! */ |
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374 | else if (energy > highEnergyLimit*a1) energy=highEnergyLimit*a1; /* constant MFP at high energy */ |
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375 | |
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376 | G4double fz1=incoming->GetDefinition()->GetPDGCharge(); |
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377 | G4int z1=(G4int)(fz1/eplus + 0.5); |
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378 | |
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379 | std::map<G4int, G4ScreenedCoulombCrossSection*>::iterator xh= |
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380 | crossSectionHandlers.find(z1); |
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381 | G4ScreenedCoulombCrossSection *xs; |
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382 | |
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383 | if (xh==crossSectionHandlers.end()) { |
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384 | xs =crossSectionHandlers[z1]=GetNewCrossSectionHandler(); |
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385 | xs->LoadData(screeningKey, z1, a1, physicsCutoff); |
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386 | xs->BuildMFPTables(); |
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387 | } else xs=(*xh).second; |
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388 | |
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389 | const G4MaterialCutsCouple* materialCouple = track.GetMaterialCutsCouple(); |
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390 | size_t materialIndex = materialCouple->GetMaterial()->GetIndex(); |
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391 | |
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392 | c2_function<G4double> &mfp=*(*xs)[materialIndex]; |
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393 | |
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394 | // make absolutely certain we don't get an out-of-range energy |
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395 | meanFreePath = mfp(std::min(std::max(energy, mfp.xmin()), mfp.xmax())); |
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396 | |
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397 | // G4cout << "MFP: " << meanFreePath << " index " << materialIndex << " energy " << energy << " MFPScale " << MFPScale << G4endl; |
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398 | |
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399 | return meanFreePath*MFPScale; |
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400 | } |
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401 | |
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402 | G4VParticleChange* G4ScreenedNuclearRecoil::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep) |
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403 | { |
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404 | validCollision=1; |
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405 | aParticleChange.Initialize(aTrack); |
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406 | NIEL=0.0; // default is no NIEL deposited |
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407 | |
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408 | // do universal setup |
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409 | |
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410 | const G4DynamicParticle* incidentParticle = aTrack.GetDynamicParticle(); |
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411 | G4ParticleDefinition *baseParticle=aTrack.GetDefinition(); |
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412 | |
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413 | G4double fz1=baseParticle->GetPDGCharge()/eplus; |
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414 | G4int z1=(G4int)(fz1+0.5); |
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415 | G4double incidentEnergy = incidentParticle->GetKineticEnergy(); |
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416 | |
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417 | // Select randomly one element and (possibly) isotope in the current material. |
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418 | const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple(); |
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419 | |
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420 | if(incidentEnergy < GetRecoilCutoff()) { // check energy sanity on entry |
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421 | if(!baseParticle->GetProcessManager()-> |
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422 | GetAtRestProcessVector()->size()) |
---|
423 | aParticleChange.ProposeTrackStatus(fStopAndKill); |
---|
424 | else |
---|
425 | aParticleChange.ProposeTrackStatus(fStopButAlive); |
---|
426 | |
---|
427 | AddToNIEL(incidentEnergy); |
---|
428 | aParticleChange.ProposeEnergy(0.0); |
---|
429 | // stop the particle and bail out |
---|
430 | validCollision=0; |
---|
431 | } |
---|
432 | |
---|
433 | const G4Material* mat = couple->GetMaterial(); |
---|
434 | G4double numberDensity=mat->GetTotNbOfAtomsPerVolume(); |
---|
435 | G4double lattice=0.5/std::pow(numberDensity,1.0/3.0); // typical lattice half-spacing |
---|
436 | G4double length=GetCurrentInteractionLength(); |
---|
437 | G4double sigopi=1.0/(CLHEP::pi*numberDensity*length); // this is sigma0/pi |
---|
438 | |
---|
439 | // compute the impact parameter very early, so if is rejected as too far away, little effort is wasted |
---|
440 | // this is the TRIM method for determining an impact parameter based on the flight path |
---|
441 | // this gives a cumulative distribution of N(P)= 1-exp(-pi P^2 n l) |
---|
442 | // which says the probability of NOT hitting a disk of area sigma= pi P^2 =exp(-sigma N l) |
---|
443 | // which may be reasonable |
---|
444 | G4double P; |
---|
445 | if(sigopi < lattice*lattice) { |
---|
446 | // normal long-flight approximation |
---|
447 | P = std::sqrt(-std::log(G4UniformRand()) *sigopi); |
---|
448 | } else { |
---|
449 | // short-flight limit |
---|
450 | P = std::sqrt(G4UniformRand())*lattice; |
---|
451 | } |
---|
452 | |
---|
453 | G4double fraction=GetHardeningFraction(); |
---|
454 | if(fraction && G4UniformRand() < fraction) { |
---|
455 | // pick out some events, and increase the central cross section |
---|
456 | // by reducing the impact parameter |
---|
457 | P /= std::sqrt(GetHardeningFactor()); |
---|
458 | } |
---|
459 | |
---|
460 | |
---|
461 | // check if we are far enough away that the energy transfer must be below cutoff, |
---|
462 | // and leave everything alone if so, saving a lot of time. |
---|
463 | if(P*P > sigopi) { |
---|
464 | if(GetVerboseLevel() > 1) |
---|
465 | printf("ScreenedNuclear impact reject: length=%.3f P=%.4f limit=%.4f\n", |
---|
466 | length/angstrom, P/angstrom,std::sqrt(sigopi)/angstrom); |
---|
467 | // no collision, don't follow up with anything |
---|
468 | validCollision=0; |
---|
469 | } |
---|
470 | |
---|
471 | // find out what we hit, and record it in our kinematics block. |
---|
472 | if(validCollision) { |
---|
473 | G4ScreenedCoulombCrossSection *xsect=GetCrossSectionHandlers()[z1]; |
---|
474 | G4ParticleDefinition *recoilIon= |
---|
475 | xsect->SelectRandomUnweightedTarget(couple); |
---|
476 | kinematics.crossSection=xsect; |
---|
477 | kinematics.recoilIon=recoilIon; |
---|
478 | kinematics.impactParameter=P; |
---|
479 | kinematics.a1=baseParticle->GetPDGMass()/amu_c2; |
---|
480 | kinematics.a2=recoilIon->GetPDGMass()/amu_c2; |
---|
481 | } else { |
---|
482 | kinematics.recoilIon=0; |
---|
483 | kinematics.impactParameter=0; |
---|
484 | kinematics.a1=baseParticle->GetPDGMass()/amu_c2; |
---|
485 | kinematics.a2=0; |
---|
486 | } |
---|
487 | |
---|
488 | std::vector<G4ScreenedCollisionStage *>::iterator stage=collisionStages.begin(); |
---|
489 | |
---|
490 | for(; stage != collisionStages.end(); stage++) |
---|
491 | (*stage)->DoCollisionStep(this,aTrack, aStep); |
---|
492 | |
---|
493 | if(registerDepositedEnergy) { |
---|
494 | aParticleChange.ProposeLocalEnergyDeposit(NIEL); |
---|
495 | aParticleChange.ProposeNonIonizingEnergyDeposit(NIEL); |
---|
496 | } |
---|
497 | return G4VDiscreteProcess::PostStepDoIt( aTrack, aStep ); |
---|
498 | } |
---|
499 | |
---|
500 | G4bool G4ScreenedCoulombClassicalKinematics::DoScreeningComputation(G4ScreenedNuclearRecoil *master, |
---|
501 | const G4ScreeningTables *screen, G4double eps, G4double beta) |
---|
502 | { |
---|
503 | G4double au=screen->au; |
---|
504 | G4CoulombKinematicsInfo &kin=master->GetKinematics(); |
---|
505 | G4double A=kin.a2; |
---|
506 | G4double a1=kin.a1; |
---|
507 | |
---|
508 | G4double xx0; // first estimate of closest approach |
---|
509 | if(eps < 5.0) { |
---|
510 | G4double y=std::log(eps); |
---|
511 | G4double mlrho4=((((3.517e-4*y+1.401e-2)*y+2.393e-1)*y+2.734)*y+2.220); |
---|
512 | G4double rho4=std::exp(-mlrho4); // W&M eq. 18 |
---|
513 | G4double bb2=0.5*beta*beta; |
---|
514 | xx0=std::sqrt(bb2+std::sqrt(bb2*bb2+rho4)); // W&M eq. 17 |
---|
515 | } else { |
---|
516 | G4double ee=1.0/(2.0*eps); |
---|
517 | xx0=ee+std::sqrt(ee*ee+beta*beta); // W&M eq. 15 (Rutherford value) |
---|
518 | if(master->CheckNuclearCollision(A, a1, xx0*au)) return 0; // nuclei too close |
---|
519 | |
---|
520 | } |
---|
521 | |
---|
522 | c2_function<G4double> &phiData=*(screen->EMphiData); |
---|
523 | // instantiate all the needed functions statically, so no allocation is done at run time |
---|
524 | // we will be solving x^2 - x phi(x*au)/eps - beta^2 == 0.0 |
---|
525 | // or, for easier scaling, x'^2 - x' au phi(x')/eps - beta^2 au^2 |
---|
526 | static c2_plugin_function<G4double> phifunc; |
---|
527 | static c2_quadratic<G4double> xsq(0., 0., 0., 1.); // x^2 |
---|
528 | static c2_linear<G4double> xovereps(0., 0., 0.); // will fill this in with the right slope at run time |
---|
529 | static c2_function<G4double> &xphi=xovereps*phifunc; |
---|
530 | static c2_function<G4double> &diff=xsq-xphi; |
---|
531 | |
---|
532 | xovereps.reset(0., 0.0, au/eps); // slope of x*au/eps term |
---|
533 | phifunc.set_function(phiData); // install interpolating table |
---|
534 | |
---|
535 | G4double xx1, phip, phip2; |
---|
536 | G4int root_error; |
---|
537 | |
---|
538 | xx1=diff.find_root(phiData.xmin(), std::min(10*xx0*au,phiData.xmax()), |
---|
539 | std::min(xx0*au, phiData.xmax()), beta*beta*au*au, &root_error, &phip, &phip2)/au; |
---|
540 | |
---|
541 | if(root_error) { |
---|
542 | G4cout << "Screened Coulomb Root Finder Error" << G4endl; |
---|
543 | G4cout << "au " << au << " A " << A << " a1 " << a1 << " xx1 " << xx1 << " eps " << eps << " beta " << beta << G4endl; |
---|
544 | G4cout << " xmin " << phiData.xmin() << " xmax " << std::min(10*xx0*au,phiData.xmax()) ; |
---|
545 | G4cout << " f(xmin) " << phifunc(phiData.xmin()) << " f(xmax) " << phifunc(std::min(10*xx0*au,phiData.xmax())) ; |
---|
546 | G4cout << " xstart " << std::min(xx0*au, phiData.xmax()) << " target " << beta*beta*au*au ; |
---|
547 | G4cout << G4endl; |
---|
548 | throw c2_exception("Failed root find"); |
---|
549 | } |
---|
550 | |
---|
551 | phifunc.unset_function(); // throws an exception if used without setting again |
---|
552 | // phiprime is scaled by one factor of au because phi is evaluated at (xx0*au), |
---|
553 | G4double phiprime=phip*au; |
---|
554 | |
---|
555 | //lambda0 is from W&M 19 |
---|
556 | G4double lambda0=1.0/std::sqrt(0.5+beta*beta/(2.0*xx1*xx1)-phiprime/(2.0*eps)); |
---|
557 | |
---|
558 | //compute the 6-term Lobatto integral alpha (per W&M 21, with different coefficients) |
---|
559 | // this is probably completely un-needed but gives the highest quality results, |
---|
560 | G4double alpha=(1.0+ lambda0)/30.0; |
---|
561 | G4double xvals[]={0.98302349, 0.84652241, 0.53235309, 0.18347974}; |
---|
562 | G4double weights[]={0.03472124, 0.14769029, 0.23485003, 0.18602489}; |
---|
563 | for(G4int k=0; k<4; k++) { |
---|
564 | G4double x, ff; |
---|
565 | x=xx1/xvals[k]; |
---|
566 | ff=1.0/std::sqrt(1.0-phiData(x*au)/(x*eps)-beta*beta/(x*x)); |
---|
567 | alpha+=weights[k]*ff; |
---|
568 | } |
---|
569 | |
---|
570 | G4double thetac1=CLHEP::pi*beta*alpha/xx1; // complement of CM scattering angle |
---|
571 | G4double sintheta=std::sin(thetac1); //note sin(pi-theta)=sin(theta) |
---|
572 | G4double costheta=-std::cos(thetac1); // note cos(pi-theta)=-cos(theta) |
---|
573 | // G4double psi=std::atan2(sintheta, costheta+a1/A); // lab scattering angle (M&T 3rd eq. 8.69) |
---|
574 | |
---|
575 | // numerics note: because we checked above for reasonable values of beta which give real recoils, |
---|
576 | // we don't have to look too closely for theta -> 0 here (which would cause sin(theta) |
---|
577 | // and 1-cos(theta) to both vanish and make the atan2 ill behaved). |
---|
578 | G4double zeta=std::atan2(sintheta, 1-costheta); // lab recoil angle (M&T 3rd eq. 8.73) |
---|
579 | G4double coszeta=std::cos(zeta); |
---|
580 | G4double sinzeta=std::sin(zeta); |
---|
581 | |
---|
582 | kin.sinTheta=sintheta; |
---|
583 | kin.cosTheta=costheta; |
---|
584 | kin.sinZeta=sinzeta; |
---|
585 | kin.cosZeta=coszeta; |
---|
586 | return 1; // all OK, collision is valid |
---|
587 | } |
---|
588 | |
---|
589 | void G4ScreenedCoulombClassicalKinematics::DoCollisionStep(G4ScreenedNuclearRecoil *master, |
---|
590 | const G4Track& aTrack, const G4Step&) { |
---|
591 | |
---|
592 | if(!master->GetValidCollision()) return; |
---|
593 | |
---|
594 | G4ParticleChange &aParticleChange=master->GetParticleChange(); |
---|
595 | G4CoulombKinematicsInfo &kin=master->GetKinematics(); |
---|
596 | |
---|
597 | const G4DynamicParticle* incidentParticle = aTrack.GetDynamicParticle(); |
---|
598 | G4ParticleDefinition *baseParticle=aTrack.GetDefinition(); |
---|
599 | |
---|
600 | G4double incidentEnergy = incidentParticle->GetKineticEnergy(); |
---|
601 | |
---|
602 | // this adjustment to a1 gives the right results for soft (constant gamma) |
---|
603 | // relativistic collisions. Hard collisions are wrong anyway, since the |
---|
604 | // Coulombic and hadronic terms interfere and cannot be added. |
---|
605 | G4double gamma=(1.0+incidentEnergy/baseParticle->GetPDGMass()); |
---|
606 | G4double a1=kin.a1*gamma; // relativistic gamma correction |
---|
607 | |
---|
608 | G4ParticleDefinition *recoilIon=kin.recoilIon; |
---|
609 | G4double A=recoilIon->GetPDGMass()/amu_c2; |
---|
610 | G4int Z=(G4int)((recoilIon->GetPDGCharge()/eplus)+0.5); |
---|
611 | |
---|
612 | G4double Ec = incidentEnergy*(A/(A+a1)); // energy in CM frame (non-relativistic!) |
---|
613 | const G4ScreeningTables *screen=kin.crossSection->GetScreening(Z); |
---|
614 | G4double au=screen->au; // screening length |
---|
615 | |
---|
616 | G4double beta = kin.impactParameter/au; // dimensionless impact parameter |
---|
617 | G4double eps = Ec/(screen->z1*Z*elm_coupling/au); // dimensionless energy |
---|
618 | |
---|
619 | G4bool ok=DoScreeningComputation(master, screen, eps, beta); |
---|
620 | if(!ok) { |
---|
621 | master->SetValidCollision(0); // flag bad collision |
---|
622 | return; // just bail out without setting valid flag |
---|
623 | } |
---|
624 | |
---|
625 | G4double eRecoil=4*incidentEnergy*a1*A*kin.cosZeta*kin.cosZeta/((a1+A)*(a1+A)); |
---|
626 | kin.eRecoil=eRecoil; |
---|
627 | |
---|
628 | if(incidentEnergy-eRecoil < master->GetRecoilCutoff()) { |
---|
629 | if(!baseParticle->GetProcessManager()-> |
---|
630 | GetAtRestProcessVector()->size()) |
---|
631 | aParticleChange.ProposeTrackStatus(fStopAndKill); |
---|
632 | else |
---|
633 | aParticleChange.ProposeTrackStatus(fStopButAlive); |
---|
634 | aParticleChange.ProposeEnergy(0.0); |
---|
635 | master->AddToNIEL(incidentEnergy-eRecoil); |
---|
636 | } |
---|
637 | |
---|
638 | if(master->GetEnableRecoils() && eRecoil > master->GetRecoilCutoff()) { |
---|
639 | kin.recoilIon=recoilIon; |
---|
640 | } else { |
---|
641 | kin.recoilIon=0; // this flags no recoil to be generated |
---|
642 | master->AddToNIEL(eRecoil) ; |
---|
643 | } |
---|
644 | } |
---|
645 | |
---|
646 | void G4SingleScatter::DoCollisionStep(G4ScreenedNuclearRecoil *master, |
---|
647 | const G4Track& aTrack, const G4Step&) { |
---|
648 | |
---|
649 | if(!master->GetValidCollision()) return; |
---|
650 | |
---|
651 | G4CoulombKinematicsInfo &kin=master->GetKinematics(); |
---|
652 | G4ParticleChange &aParticleChange=master->GetParticleChange(); |
---|
653 | |
---|
654 | const G4DynamicParticle* incidentParticle = aTrack.GetDynamicParticle(); |
---|
655 | G4double incidentEnergy = incidentParticle->GetKineticEnergy(); |
---|
656 | G4double eRecoil=kin.eRecoil; |
---|
657 | |
---|
658 | G4double azimuth=G4UniformRand()*(2.0*CLHEP::pi); |
---|
659 | G4double sa=std::sin(azimuth); |
---|
660 | G4double ca=std::cos(azimuth); |
---|
661 | |
---|
662 | G4ThreeVector recoilMomentumDirection(kin.sinZeta*ca, kin.sinZeta*sa, kin.cosZeta); |
---|
663 | G4ParticleMomentum incidentDirection = incidentParticle->GetMomentumDirection(); |
---|
664 | recoilMomentumDirection=recoilMomentumDirection.rotateUz(incidentDirection); |
---|
665 | G4ThreeVector recoilMomentum=recoilMomentumDirection*std::sqrt(2.0*eRecoil*kin.a2*amu_c2); |
---|
666 | |
---|
667 | if(aParticleChange.GetEnergy() != 0.0) { // DoKinematics hasn't stopped it! |
---|
668 | G4ThreeVector beamMomentum=incidentParticle->GetMomentum()-recoilMomentum; |
---|
669 | aParticleChange.ProposeMomentumDirection(beamMomentum.unit()) ; |
---|
670 | aParticleChange.ProposeEnergy(incidentEnergy-eRecoil); |
---|
671 | } |
---|
672 | |
---|
673 | if(kin.recoilIon) { |
---|
674 | G4DynamicParticle* recoil = new G4DynamicParticle (kin.recoilIon, |
---|
675 | recoilMomentumDirection,eRecoil) ; |
---|
676 | |
---|
677 | aParticleChange.SetNumberOfSecondaries(1); |
---|
678 | aParticleChange.AddSecondary(recoil); |
---|
679 | } |
---|
680 | } |
---|
681 | |
---|
682 | G4bool G4ScreenedNuclearRecoil:: |
---|
683 | IsApplicable(const G4ParticleDefinition& aParticleType) |
---|
684 | { |
---|
685 | return aParticleType == *(G4Proton::Proton()) || |
---|
686 | aParticleType.GetParticleType() == "nucleus" || |
---|
687 | aParticleType.GetParticleType() == "static_nucleus"; |
---|
688 | } |
---|
689 | |
---|
690 | |
---|
691 | void |
---|
692 | G4ScreenedNuclearRecoil:: |
---|
693 | DumpPhysicsTable(const G4ParticleDefinition&) |
---|
694 | { |
---|
695 | } |
---|
696 | |
---|
697 | // This used to be the file mhmScreenedNuclearRecoil_native.cc |
---|
698 | // it has been included here to collect this file into a smaller number of packages |
---|
699 | |
---|
700 | #include "G4DataVector.hh" |
---|
701 | #include "G4Material.hh" |
---|
702 | #include "G4Element.hh" |
---|
703 | #include "G4Isotope.hh" |
---|
704 | #include "G4MaterialCutsCouple.hh" |
---|
705 | #include "G4ElementVector.hh" |
---|
706 | #include <vector> |
---|
707 | |
---|
708 | static c2_function<G4double> &ZBLScreening(G4int z1, G4int z2, size_t npoints, G4double rMax, G4double *auval) |
---|
709 | { |
---|
710 | static const size_t ncoef=4; |
---|
711 | static G4double scales[ncoef]={-3.2, -0.9432, -0.4028, -0.2016}; |
---|
712 | static G4double coefs[ncoef]={0.1818,0.5099,0.2802,0.0281}; |
---|
713 | |
---|
714 | G4double au=0.8854*angstrom*0.529/(std::pow(z1, 0.23)+std::pow(z2,0.23)); |
---|
715 | std::vector<G4double> r(npoints), phi(npoints); |
---|
716 | |
---|
717 | for(size_t i=0; i<npoints; i++) { |
---|
718 | G4double rr=(float)i/(float)(npoints-1); |
---|
719 | r[i]=rr*rr*rMax; // use quadratic r scale to make sampling fine near the center |
---|
720 | G4double sum=0.0; |
---|
721 | for(size_t j=0; j<ncoef; j++) sum+=coefs[j]*std::exp(scales[j]*r[i]/au); |
---|
722 | phi[i]=sum; |
---|
723 | } |
---|
724 | |
---|
725 | // compute the derivative at the origin for the spline |
---|
726 | G4double phiprime0=0.0; |
---|
727 | for(size_t j=0; j<ncoef; j++) phiprime0+=scales[j]*coefs[j]*std::exp(scales[j]*r[0]/au); |
---|
728 | phiprime0*=(1.0/au); // put back in natural units; |
---|
729 | |
---|
730 | *auval=au; |
---|
731 | return *static_cast<c2_function<G4double> *>(new lin_log_interpolating_function<G4double>(r, phi, false, phiprime0)); |
---|
732 | } |
---|
733 | |
---|
734 | static c2_function<G4double> &MoliereScreening(G4int z1, G4int z2, size_t npoints, G4double rMax, G4double *auval) |
---|
735 | { |
---|
736 | static const size_t ncoef=3; |
---|
737 | static G4double scales[ncoef]={-6.0, -1.2, -0.3}; |
---|
738 | static G4double coefs[ncoef]={0.10, 0.55, 0.35}; |
---|
739 | |
---|
740 | G4double au=0.8853*0.529*angstrom/std::sqrt(std::pow(z1, 0.6667)+std::pow(z2,0.6667)); |
---|
741 | std::vector<G4double> r(npoints), phi(npoints); |
---|
742 | |
---|
743 | for(size_t i=0; i<npoints; i++) { |
---|
744 | G4double rr=(float)i/(float)(npoints-1); |
---|
745 | r[i]=rr*rr*rMax; // use quadratic r scale to make sampling fine near the center |
---|
746 | G4double sum=0.0; |
---|
747 | for(size_t j=0; j<ncoef; j++) sum+=coefs[j]*std::exp(scales[j]*r[i]/au); |
---|
748 | phi[i]=sum; |
---|
749 | } |
---|
750 | |
---|
751 | // compute the derivative at the origin for the spline |
---|
752 | G4double phiprime0=0.0; |
---|
753 | for(size_t j=0; j<ncoef; j++) phiprime0+=scales[j]*coefs[j]*std::exp(scales[j]*r[0]/au); |
---|
754 | phiprime0*=(1.0/au); // put back in natural units; |
---|
755 | |
---|
756 | *auval=au; |
---|
757 | return *static_cast<c2_function<G4double> *>(new lin_log_interpolating_function<G4double>(r, phi, false, phiprime0)); |
---|
758 | } |
---|
759 | |
---|
760 | static c2_function<G4double> &LJScreening(G4int z1, G4int z2, size_t npoints, G4double rMax, G4double *auval) |
---|
761 | { |
---|
762 | //from Loftager, Besenbacher, Jensen & Sorensen |
---|
763 | //PhysRev A20, 1443++, 1979 |
---|
764 | G4double au=0.8853*0.529*angstrom/std::sqrt(std::pow(z1, 0.6667)+std::pow(z2,0.6667)); |
---|
765 | std::vector<G4double> r(npoints), phi(npoints); |
---|
766 | |
---|
767 | for(size_t i=0; i<npoints; i++) { |
---|
768 | G4double rr=(float)i/(float)(npoints-1); |
---|
769 | r[i]=rr*rr*rMax; // use quadratic r scale to make sampling fine near the center |
---|
770 | |
---|
771 | G4double y=std::sqrt(9.67*r[i]/au); |
---|
772 | G4double ysq=y*y; |
---|
773 | G4double phipoly=1+y+0.3344*ysq+0.0485*y*ysq+0.002647*ysq*ysq; |
---|
774 | phi[i]=phipoly*std::exp(-y); |
---|
775 | // G4cout << r[i] << " " << phi[i] << G4endl; |
---|
776 | } |
---|
777 | |
---|
778 | // compute the derivative at the origin for the spline |
---|
779 | G4double logphiprime0=(9.67/2.0)*(2*0.3344-1.0); // #avoid 0/0 on first element |
---|
780 | logphiprime0 *= (1.0/au); // #put back in natural units |
---|
781 | |
---|
782 | *auval=au; |
---|
783 | return *static_cast<c2_function<G4double> *>(new lin_log_interpolating_function<G4double>(r, phi, false, logphiprime0*phi[0])); |
---|
784 | } |
---|
785 | |
---|
786 | G4NativeScreenedCoulombCrossSection::~G4NativeScreenedCoulombCrossSection() { |
---|
787 | } |
---|
788 | |
---|
789 | G4NativeScreenedCoulombCrossSection::G4NativeScreenedCoulombCrossSection() { |
---|
790 | AddScreeningFunction("zbl", ZBLScreening); |
---|
791 | AddScreeningFunction("lj", LJScreening); |
---|
792 | AddScreeningFunction("mol", MoliereScreening); |
---|
793 | } |
---|
794 | |
---|
795 | std::vector<G4String> G4NativeScreenedCoulombCrossSection::GetScreeningKeys() const { |
---|
796 | std::vector<G4String> keys; |
---|
797 | // find the available screening keys |
---|
798 | std::map<std::string, ScreeningFunc>::const_iterator sfunciter=phiMap.begin(); |
---|
799 | for(; sfunciter != phiMap.end(); sfunciter++) keys.push_back((*sfunciter).first); |
---|
800 | return keys; |
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801 | } |
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802 | |
---|
803 | static inline G4double cm_energy(G4double a1, G4double a2, G4double t0) { |
---|
804 | // "relativistically correct energy in CM frame" |
---|
805 | G4double m1=a1*amu_c2, m2=a2*amu_c2; |
---|
806 | G4double mc2=(m1+m2); |
---|
807 | G4double f=2.0*m2*t0/(mc2*mc2); |
---|
808 | // old way: return (f < 1e-6) ? 0.5*mc2*f : mc2*(std::sqrt(1.0+f)-1.0); |
---|
809 | // formally equivalent to previous, but numerically stable for all f without conditional |
---|
810 | // uses identity (sqrt(1+x) - 1)(sqrt(1+x) + 1) = x |
---|
811 | return mc2*f/(std::sqrt(1.0+f)+1.0); |
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812 | } |
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813 | |
---|
814 | static inline G4double thetac(G4double m1, G4double m2, G4double eratio) { |
---|
815 | G4double s2th2=eratio*( (m1+m2)*(m1+m2)/(4.0*m1*m2) ); |
---|
816 | G4double sth2=std::sqrt(s2th2); |
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817 | return 2.0*std::asin(sth2); |
---|
818 | } |
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819 | |
---|
820 | void G4NativeScreenedCoulombCrossSection::LoadData(G4String screeningKey, G4int z1, G4double a1, G4double recoilCutoff) |
---|
821 | { |
---|
822 | static const size_t sigLen=200; // since sigma doesn't matter much, a very coarse table will do |
---|
823 | G4DataVector energies(sigLen); |
---|
824 | G4DataVector data(sigLen); |
---|
825 | |
---|
826 | a1=standardmass(z1); // use standardized values for mass for building tables |
---|
827 | |
---|
828 | const G4MaterialTable* materialTable = G4Material::GetMaterialTable(); |
---|
829 | if (materialTable == 0) |
---|
830 | G4Exception("mhmNativeCrossSection::LoadData - no MaterialTable found)"); |
---|
831 | |
---|
832 | G4int nMaterials = G4Material::GetNumberOfMaterials(); |
---|
833 | |
---|
834 | for (G4int m=0; m<nMaterials; m++) |
---|
835 | { |
---|
836 | const G4Material* material= (*materialTable)[m]; |
---|
837 | const G4ElementVector* elementVector = material->GetElementVector(); |
---|
838 | const G4int nMatElements = material->GetNumberOfElements(); |
---|
839 | |
---|
840 | for (G4int iEl=0; iEl<nMatElements; iEl++) |
---|
841 | { |
---|
842 | G4Element* element = (*elementVector)[iEl]; |
---|
843 | G4int Z = (G4int) element->GetZ(); |
---|
844 | G4double a2=element->GetA()*(mole/gram); |
---|
845 | |
---|
846 | if(sigmaMap.find(Z)!=sigmaMap.end()) continue; // we've already got this element |
---|
847 | |
---|
848 | // find the screening function generator we need |
---|
849 | std::map<std::string, ScreeningFunc>::iterator sfunciter=phiMap.find(screeningKey); |
---|
850 | if(sfunciter==phiMap.end()) { |
---|
851 | G4cout << "no such screening key " << screeningKey << G4endl; // FIXME later |
---|
852 | exit(1); |
---|
853 | } |
---|
854 | ScreeningFunc sfunc=(*sfunciter).second; |
---|
855 | |
---|
856 | G4double au; |
---|
857 | c2_function<G4double> &screen=sfunc(z1, Z, 200, 50.0*angstrom, &au); // generate the screening data |
---|
858 | |
---|
859 | G4ScreeningTables st; |
---|
860 | st.EMphiData=&screen; // this is our phi table |
---|
861 | st.z1=z1; st.m1=a1; st.z2=Z; st.m2=a2; st.emin=recoilCutoff; |
---|
862 | st.au=au; |
---|
863 | |
---|
864 | // now comes the hard part... build the total cross section tables from the phi table |
---|
865 | //based on (pi-thetac) = pi*beta*alpha/x0, but noting that alpha is very nearly unity, always |
---|
866 | //so just solve it wth alpha=1, which makes the solution much easier |
---|
867 | //this function returns an approximation to (beta/x0)^2=phi(x0)/(eps*x0)-1 ~ ((pi-thetac)/pi)^2 |
---|
868 | //Since we don't need exact sigma values, this is good enough (within a factor of 2 almost always) |
---|
869 | //this rearranges to phi(x0)/(x0*eps) = 2*theta/pi - theta^2/pi^2 |
---|
870 | |
---|
871 | c2_linear<G4double> c2au(0.0, 0.0, au); |
---|
872 | c2_composed_function<G4double> phiau(screen, c2au); // build phi(x*au) for dimensionless phi |
---|
873 | c2_linear<G4double> c2eps(0.0, 0.0, 0.0); // will store an appropriate eps inside this in loop |
---|
874 | c2_ratio<G4double> x0func(phiau, c2eps); // this will be phi(x)/(x*eps) when c2eps is correctly set |
---|
875 | |
---|
876 | G4double m1c2=a1*amu_c2; |
---|
877 | G4double escale=z1*Z*elm_coupling/au; // energy at screening distance |
---|
878 | G4double emax=m1c2; // model is doubtful in very relativistic range |
---|
879 | G4double eratkin=0.9999*(4*a1*a2)/((a1+a2)*(a1+a2)); // #maximum kinematic ratio possible at 180 degrees |
---|
880 | G4double cmfact0=st.emin/cm_energy(a1, a2, st.emin); |
---|
881 | G4double l1=std::log(emax); |
---|
882 | G4double l0=std::log(st.emin*cmfact0/eratkin); |
---|
883 | |
---|
884 | if(verbosity >=1) |
---|
885 | G4cout << "Native Screening: " << screeningKey << " " << z1 << " " << a1 << " " << |
---|
886 | Z << " " << a2 << " " << recoilCutoff << G4endl; |
---|
887 | |
---|
888 | for(size_t idx=0; idx<sigLen; idx++) { |
---|
889 | G4double ee=std::exp(idx*((l1-l0)/sigLen)+l0); |
---|
890 | G4double gamma=1.0+ee/m1c2; |
---|
891 | G4double eratio=(cmfact0*st.emin)/ee; // factor by which ee needs to be reduced to get emin |
---|
892 | G4double theta=thetac(gamma*a1, a2, eratio); |
---|
893 | |
---|
894 | G4double eps=cm_energy(a1, a2, ee)/escale; // #make sure lab energy is converted to CM for these calculations |
---|
895 | c2eps.reset(0.0, 0.0, eps); // set correct slope in this function |
---|
896 | |
---|
897 | G4double q=theta/pi; |
---|
898 | // G4cout << ee << " " << m1c2 << " " << gamma << " " << eps << " " << theta << " " << q << G4endl; |
---|
899 | G4double x0= x0func.find_root(1e-6*angstrom/au, 0.9999*screen.xmax()/au, 1.0, 2*q-q*q); |
---|
900 | G4double betasquared=x0*x0 - x0*phiau(x0)/eps; |
---|
901 | G4double sigma=pi*betasquared*au*au; |
---|
902 | energies[idx]=ee; |
---|
903 | data[idx]=sigma; |
---|
904 | } |
---|
905 | |
---|
906 | screeningData[Z]=st; |
---|
907 | sigmaMap[Z] = static_cast<c2_function<G4double> *>(new log_log_interpolating_function<G4double>( |
---|
908 | energies, data)); |
---|
909 | } |
---|
910 | } |
---|
911 | } |
---|