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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4mplIonisationModel.cc,v 1.6 2009/02/20 16:38:33 vnivanch Exp $ |
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27 | // GEANT4 tag $Name: geant4-09-02-ref-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: G4mplIonisationModel |
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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 "G4mplIonisationModel.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 | |
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62 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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63 | |
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64 | using namespace std; |
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65 | |
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66 | G4mplIonisationModel::G4mplIonisationModel(G4double mCharge, const G4String& nam) |
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67 | : G4VEmModel(nam),G4VEmFluctuationModel(nam), |
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68 | magCharge(mCharge), |
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69 | twoln10(log(100.0)), |
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70 | betalow(0.01), |
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71 | betalim(0.1), |
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72 | beta2lim(betalim*betalim), |
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73 | bg2lim(beta2lim*(1.0 + beta2lim)) |
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74 | { |
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75 | nmpl = G4int(abs(magCharge) * 2 * fine_structure_const + 0.5); |
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76 | if(nmpl > 6) nmpl = 6; |
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77 | else if(nmpl < 1) nmpl = 1; |
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78 | pi_hbarc2_over_mc2 = pi * hbarc * hbarc / electron_mass_c2; |
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79 | chargeSquare = magCharge * magCharge; |
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80 | dedxlim = 45.*nmpl*nmpl*GeV*cm2/g; |
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81 | } |
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82 | |
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83 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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84 | |
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85 | G4mplIonisationModel::~G4mplIonisationModel() |
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86 | {} |
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87 | |
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88 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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89 | |
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90 | void G4mplIonisationModel::Initialise(const G4ParticleDefinition* p, |
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91 | const G4DataVector&) |
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92 | { |
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93 | monopole = p; |
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94 | mass = monopole->GetPDGMass(); |
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95 | |
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96 | if(pParticleChange) |
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97 | fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*>(pParticleChange); |
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98 | else |
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99 | fParticleChange = new G4ParticleChangeForLoss(); |
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100 | } |
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101 | |
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102 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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103 | |
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104 | G4double G4mplIonisationModel::ComputeDEDXPerVolume(const G4Material* material, |
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105 | const G4ParticleDefinition*, |
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106 | G4double kineticEnergy, |
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107 | G4double) |
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108 | { |
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109 | G4double tau = kineticEnergy / mass; |
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110 | G4double gam = tau + 1.0; |
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111 | G4double bg2 = tau * (tau + 2.0); |
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112 | G4double beta2 = bg2 / (gam * gam); |
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113 | G4double beta = sqrt(beta2); |
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114 | |
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115 | // low-energy asymptotic formula |
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116 | G4double dedx = dedxlim*beta*material->GetDensity(); |
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117 | |
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118 | // above asymptotic |
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119 | if(beta > betalow) { |
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120 | |
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121 | // high energy |
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122 | if(beta >= betalim) { |
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123 | dedx = ComputeDEDXAhlen(material, bg2); |
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124 | |
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125 | } else { |
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126 | |
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127 | G4double dedx1 = dedxlim*betalow*material->GetDensity(); |
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128 | G4double dedx2 = ComputeDEDXAhlen(material, bg2lim); |
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129 | |
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130 | // extrapolation between two formula |
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131 | G4double kapa2 = beta - betalow; |
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132 | G4double kapa1 = betalim - beta; |
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133 | dedx = (kapa1*dedx1 + kapa2*dedx2)/(kapa1 + kapa2); |
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134 | } |
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135 | } |
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136 | return dedx; |
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137 | } |
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138 | |
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139 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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140 | |
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141 | G4double G4mplIonisationModel::ComputeDEDXAhlen(const G4Material* material, |
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142 | G4double bg2) |
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143 | { |
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144 | G4double eDensity = material->GetElectronDensity(); |
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145 | G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy(); |
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146 | G4double cden = material->GetIonisation()->GetCdensity(); |
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147 | G4double mden = material->GetIonisation()->GetMdensity(); |
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148 | G4double aden = material->GetIonisation()->GetAdensity(); |
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149 | G4double x0den = material->GetIonisation()->GetX0density(); |
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150 | G4double x1den = material->GetIonisation()->GetX1density(); |
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151 | |
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152 | // Ahlen's formula for nonconductors, [1]p157, f(5.7) |
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153 | G4double dedx = log(2.0 * electron_mass_c2 * bg2 / eexc) - 0.5; |
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154 | |
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155 | // Kazama et al. cross-section correction |
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156 | G4double k = 0.406; |
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157 | if(nmpl > 1) k = 0.346; |
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158 | |
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159 | // Bloch correction |
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160 | const G4double B[7] = { 0.0, 0.248, 0.672, 1.022, 1.243, 1.464, 1.685}; |
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161 | |
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162 | dedx += 0.5 * k - B[nmpl]; |
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163 | |
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164 | // density effect correction |
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165 | G4double deltam; |
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166 | G4double x = log(bg2) / twoln10; |
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167 | if ( x >= x0den ) { |
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168 | deltam = twoln10 * x - cden; |
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169 | if ( x < x1den ) deltam += aden * pow((x1den-x), mden); |
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170 | dedx -= 0.5 * deltam; |
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171 | } |
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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 | void G4mplIonisationModel::SampleSecondaries(std::vector<G4DynamicParticle*>*, |
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183 | const G4MaterialCutsCouple*, |
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184 | const G4DynamicParticle*, |
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185 | G4double, |
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186 | G4double) |
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187 | {} |
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188 | |
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189 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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190 | |
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191 | G4double G4mplIonisationModel::SampleFluctuations( |
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192 | const G4Material* material, |
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193 | const G4DynamicParticle* dp, |
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194 | G4double& tmax, |
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195 | G4double& length, |
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196 | G4double& meanLoss) |
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197 | { |
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198 | G4double siga = Dispersion(material,dp,tmax,length); |
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199 | G4double loss = meanLoss; |
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200 | siga = sqrt(siga); |
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201 | G4double twomeanLoss = meanLoss + meanLoss; |
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202 | |
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203 | if(twomeanLoss < siga) { |
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204 | G4double x; |
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205 | do { |
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206 | loss = twomeanLoss*G4UniformRand(); |
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207 | x = (loss - meanLoss)/siga; |
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208 | } while (1.0 - 0.5*x*x < G4UniformRand()); |
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209 | } else { |
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210 | do { |
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211 | loss = G4RandGauss::shoot(meanLoss,siga); |
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212 | } while (0.0 > loss || loss > twomeanLoss); |
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213 | } |
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214 | return loss; |
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215 | } |
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216 | |
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217 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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218 | |
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219 | G4double G4mplIonisationModel::Dispersion(const G4Material* material, |
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220 | const G4DynamicParticle* dp, |
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221 | G4double& tmax, |
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222 | G4double& length) |
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223 | { |
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224 | G4double siga = 0.0; |
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225 | G4double tau = dp->GetKineticEnergy()/mass; |
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226 | if(tau > 0.0) { |
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227 | G4double electronDensity = material->GetElectronDensity(); |
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228 | G4double gam = tau + 1.0; |
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229 | G4double invbeta2 = (gam*gam)/(tau * (tau+2.0)); |
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230 | siga = (invbeta2 - 0.5) * twopi_mc2_rcl2 * tmax * length |
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231 | * electronDensity * chargeSquare; |
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232 | } |
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233 | return siga; |
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234 | } |
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235 | |
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236 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... |
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