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15 | // * use. Please see the license in the file LICENSE and URL above * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4mplIonisationWithDeltaModel.cc,v 1.1 2010/10/26 15:40:03 vnivanch Exp $ |
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27 | // GEANT4 tag $Name: emhighenergy-V09-03-02 $ |
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28 | // |
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29 | // ------------------------------------------------------------------- |
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30 | // |
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31 | // GEANT4 Class header file |
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32 | // |
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33 | // |
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34 | // File name: G4mplIonisationWithDeltaModel |
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35 | // |
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36 | // Author: Vladimir Ivanchenko |
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37 | // |
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38 | // Creation date: 06.09.2005 |
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39 | // |
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40 | // Modifications: |
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41 | // 12.08.2007 Changing low energy approximation and extrapolation. |
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42 | // Small bug fixing and refactoring (M. Vladymyrov) |
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43 | // 13.11.2007 Use low-energy asymptotic from [3] (V.Ivanchenko) |
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44 | // |
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45 | // |
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46 | // ------------------------------------------------------------------- |
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47 | // References |
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48 | // [1] Steven P. Ahlen: Energy loss of relativistic heavy ionizing particles, |
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49 | // S.P. Ahlen, Rev. Mod. Phys 52(1980), p121 |
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50 | // [2] K.A. Milton arXiv:hep-ex/0602040 |
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51 | // [3] S.P. Ahlen and K. Kinoshita, Phys. Rev. D26 (1982) 2347 |
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52 | |
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53 | |
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54 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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55 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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56 | |
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57 | #include "G4mplIonisationWithDeltaModel.hh" |
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58 | #include "Randomize.hh" |
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59 | #include "G4LossTableManager.hh" |
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60 | #include "G4ParticleChangeForLoss.hh" |
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61 | #include "G4Electron.hh" |
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62 | #include "G4DynamicParticle.hh" |
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63 | |
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64 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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65 | |
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66 | using namespace std; |
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67 | |
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68 | G4mplIonisationWithDeltaModel::G4mplIonisationWithDeltaModel(G4double mCharge, const G4String& nam) |
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69 | : G4VEmModel(nam),G4VEmFluctuationModel(nam), |
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70 | magCharge(mCharge), |
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71 | twoln10(log(100.0)), |
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72 | betalow(0.01), |
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73 | betalim(0.1), |
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74 | beta2lim(betalim*betalim), |
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75 | bg2lim(beta2lim*(1.0 + beta2lim)) |
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76 | { |
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77 | nmpl = G4int(abs(magCharge) * 2 * fine_structure_const + 0.5); |
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78 | if(nmpl > 6) { nmpl = 6; } |
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79 | else if(nmpl < 1) { nmpl = 1; } |
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80 | pi_hbarc2_over_mc2 = pi * hbarc * hbarc / electron_mass_c2; |
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81 | chargeSquare = magCharge * magCharge; |
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82 | dedxlim = 45.*nmpl*nmpl*GeV*cm2/g; |
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83 | fParticleChange = 0; |
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84 | theElectron = G4Electron::Electron(); |
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85 | G4cout << "### Monopole ionisation model with d-electron production, Gmag= " |
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86 | << magCharge/eplus << G4endl; |
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87 | mass = 0.0; |
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88 | } |
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89 | |
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90 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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91 | |
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92 | G4mplIonisationWithDeltaModel::~G4mplIonisationWithDeltaModel() |
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93 | {} |
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94 | |
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95 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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96 | |
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97 | void |
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98 | G4mplIonisationWithDeltaModel::Initialise(const G4ParticleDefinition* p, |
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99 | const G4DataVector&) |
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100 | { |
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101 | monopole = p; |
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102 | mass = monopole->GetPDGMass(); |
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103 | if(!fParticleChange) { fParticleChange = GetParticleChangeForLoss(); } |
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104 | } |
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105 | |
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106 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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107 | |
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108 | G4double |
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109 | G4mplIonisationWithDeltaModel::ComputeDEDXPerVolume(const G4Material* material, |
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110 | const G4ParticleDefinition* p, |
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111 | G4double kineticEnergy, |
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112 | G4double maxEnergy) |
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113 | { |
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114 | G4double tmax = MaxSecondaryEnergy(p,kineticEnergy); |
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115 | G4double cutEnergy = std::min(tmax, maxEnergy); |
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116 | G4double tau = kineticEnergy / mass; |
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117 | G4double gam = tau + 1.0; |
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118 | G4double bg2 = tau * (tau + 2.0); |
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119 | G4double beta2 = bg2 / (gam * gam); |
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120 | G4double beta = sqrt(beta2); |
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121 | |
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122 | // low-energy asymptotic formula |
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123 | G4double dedx = dedxlim*beta*material->GetDensity(); |
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124 | |
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125 | // above asymptotic |
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126 | if(beta > betalow) { |
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127 | |
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128 | // high energy |
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129 | if(beta >= betalim) { |
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130 | dedx = ComputeDEDXAhlen(material, bg2, cutEnergy); |
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131 | |
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132 | } else { |
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133 | |
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134 | G4double dedx1 = dedxlim*betalow*material->GetDensity(); |
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135 | G4double dedx2 = ComputeDEDXAhlen(material, bg2lim, cutEnergy); |
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136 | |
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137 | // extrapolation between two formula |
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138 | G4double kapa2 = beta - betalow; |
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139 | G4double kapa1 = betalim - beta; |
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140 | dedx = (kapa1*dedx1 + kapa2*dedx2)/(kapa1 + kapa2); |
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141 | } |
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142 | } |
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143 | return dedx; |
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144 | } |
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145 | |
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146 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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147 | |
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148 | G4double |
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149 | G4mplIonisationWithDeltaModel::ComputeDEDXAhlen(const G4Material* material, |
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150 | G4double bg2, |
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151 | G4double cutEnergy) |
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152 | { |
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153 | G4double eDensity = material->GetElectronDensity(); |
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154 | G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy(); |
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155 | |
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156 | // Ahlen's formula for nonconductors, [1]p157, f(5.7) |
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157 | G4double dedx = |
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158 | 0.5*(log(2.0 * electron_mass_c2 * bg2*cutEnergy / (eexc*eexc)) - 1.0); |
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159 | |
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160 | // Kazama et al. cross-section correction |
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161 | G4double k = 0.406; |
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162 | if(nmpl > 1) { k = 0.346; } |
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163 | |
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164 | // Bloch correction |
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165 | const G4double B[7] = { 0.0, 0.248, 0.672, 1.022, 1.243, 1.464, 1.685}; |
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166 | |
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167 | dedx += 0.5 * k - B[nmpl]; |
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168 | |
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169 | // density effect correction |
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170 | G4double x = log(bg2)/twoln10; |
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171 | dedx -= material->GetIonisation()->DensityCorrection(x); |
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172 | |
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173 | // now compute the total ionization loss |
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174 | dedx *= pi_hbarc2_over_mc2 * eDensity * nmpl * nmpl; |
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175 | |
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176 | if (dedx < 0.0) { dedx = 0; } |
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177 | return dedx; |
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178 | } |
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179 | |
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180 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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181 | |
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182 | G4double |
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183 | G4mplIonisationWithDeltaModel::ComputeCrossSectionPerElectron( |
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184 | const G4ParticleDefinition* p, |
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185 | G4double kineticEnergy, |
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186 | G4double cutEnergy, |
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187 | G4double maxKinEnergy) |
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188 | { |
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189 | G4double cross = 0.0; |
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190 | G4double tmax = MaxSecondaryEnergy(p, kineticEnergy); |
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191 | G4double maxEnergy = min(tmax,maxKinEnergy); |
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192 | if(cutEnergy < maxEnergy) { |
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193 | cross = (1.0/cutEnergy - 1.0/maxEnergy)*twopi_mc2_rcl2*chargeSquare; |
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194 | } |
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195 | return cross; |
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196 | } |
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197 | |
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198 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
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199 | |
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200 | G4double |
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201 | G4mplIonisationWithDeltaModel::ComputeCrossSectionPerAtom( |
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202 | const G4ParticleDefinition* p, |
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203 | G4double kineticEnergy, |
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204 | G4double Z, G4double, |
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205 | G4double cutEnergy, |
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206 | G4double maxEnergy) |
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207 | { |
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208 | G4double cross = |
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209 | Z*ComputeCrossSectionPerElectron(p,kineticEnergy,cutEnergy,maxEnergy); |
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210 | return cross; |
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211 | } |
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212 | |
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213 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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214 | |
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215 | void |
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216 | G4mplIonisationWithDeltaModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp, |
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217 | const G4MaterialCutsCouple*, |
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218 | const G4DynamicParticle* dp, |
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219 | G4double minKinEnergy, |
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220 | G4double maxEnergy) |
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221 | { |
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222 | G4double kineticEnergy = dp->GetKineticEnergy(); |
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223 | G4double tmax = MaxSecondaryEnergy(dp->GetDefinition(),kineticEnergy); |
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224 | |
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225 | G4double maxKinEnergy = std::min(maxEnergy,tmax); |
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226 | if(minKinEnergy >= maxKinEnergy) { return; } |
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227 | |
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228 | //G4cout << "G4mplIonisationWithDeltaModel::SampleSecondaries: E(GeV)= " |
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229 | // << kineticEnergy/GeV << " M(GeV)= " << mass/GeV |
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230 | // << " tmin(MeV)= " << minKinEnergy/MeV << G4endl; |
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231 | |
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232 | G4double totEnergy = kineticEnergy + mass; |
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233 | G4double etot2 = totEnergy*totEnergy; |
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234 | G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2; |
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235 | |
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236 | // sampling without nuclear size effect |
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237 | G4double q = G4UniformRand(); |
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238 | G4double deltaKinEnergy = minKinEnergy*maxKinEnergy |
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239 | /(minKinEnergy*(1.0 - q) + maxKinEnergy*q); |
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240 | |
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241 | // delta-electron is produced |
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242 | G4double totMomentum = totEnergy*sqrt(beta2); |
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243 | G4double deltaMomentum = |
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244 | sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2)); |
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245 | G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) / |
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246 | (deltaMomentum * totMomentum); |
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247 | if(cost > 1.0) { cost = 1.0; } |
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248 | |
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249 | G4double sint = sqrt((1.0 - cost)*(1.0 + cost)); |
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250 | |
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251 | G4double phi = twopi * G4UniformRand() ; |
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252 | |
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253 | G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost); |
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254 | G4ThreeVector direction = dp->GetMomentumDirection(); |
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255 | deltaDirection.rotateUz(direction); |
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256 | |
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257 | // create G4DynamicParticle object for delta ray |
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258 | G4DynamicParticle* delta = |
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259 | new G4DynamicParticle(theElectron,deltaDirection,deltaKinEnergy); |
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260 | |
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261 | vdp->push_back(delta); |
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262 | |
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263 | // Change kinematics of primary particle |
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264 | kineticEnergy -= deltaKinEnergy; |
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265 | G4ThreeVector finalP = direction*totMomentum - deltaDirection*deltaMomentum; |
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266 | finalP = finalP.unit(); |
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267 | |
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268 | fParticleChange->SetProposedKineticEnergy(kineticEnergy); |
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269 | fParticleChange->SetProposedMomentumDirection(finalP); |
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270 | } |
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271 | |
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272 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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273 | |
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274 | G4double G4mplIonisationWithDeltaModel::SampleFluctuations( |
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275 | const G4Material* material, |
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276 | const G4DynamicParticle* dp, |
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277 | G4double& tmax, |
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278 | G4double& length, |
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279 | G4double& meanLoss) |
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280 | { |
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281 | G4double siga = Dispersion(material,dp,tmax,length); |
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282 | G4double loss = meanLoss; |
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283 | siga = sqrt(siga); |
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284 | G4double twomeanLoss = meanLoss + meanLoss; |
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285 | |
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286 | if(twomeanLoss < siga) { |
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287 | G4double x; |
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288 | do { |
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289 | loss = twomeanLoss*G4UniformRand(); |
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290 | x = (loss - meanLoss)/siga; |
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291 | } while (1.0 - 0.5*x*x < G4UniformRand()); |
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292 | } else { |
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293 | do { |
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294 | loss = G4RandGauss::shoot(meanLoss,siga); |
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295 | } while (0.0 > loss || loss > twomeanLoss); |
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296 | } |
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297 | return loss; |
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298 | } |
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299 | |
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300 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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301 | |
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302 | G4double |
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303 | G4mplIonisationWithDeltaModel::Dispersion(const G4Material* material, |
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304 | const G4DynamicParticle* dp, |
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305 | G4double& tmax, |
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306 | G4double& length) |
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307 | { |
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308 | G4double siga = 0.0; |
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309 | G4double tau = dp->GetKineticEnergy()/mass; |
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310 | if(tau > 0.0) { |
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311 | G4double electronDensity = material->GetElectronDensity(); |
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312 | G4double gam = tau + 1.0; |
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313 | G4double invbeta2 = (gam*gam)/(tau * (tau+2.0)); |
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314 | siga = (invbeta2 - 0.5) * twopi_mc2_rcl2 * tmax * length |
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315 | * electronDensity * chargeSquare; |
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316 | } |
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317 | return siga; |
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318 | } |
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319 | |
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320 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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321 | |
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322 | G4double |
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323 | G4mplIonisationWithDeltaModel::MaxSecondaryEnergy(const G4ParticleDefinition*, |
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324 | G4double kinEnergy) |
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325 | { |
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326 | G4double tau = kinEnergy/mass; |
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327 | return 2.0*electron_mass_c2*tau*(tau + 2.); |
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328 | } |
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329 | |
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330 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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