1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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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: G4QSynchRad.cc,v 1.1 2009/11/17 10:36:55 mkossov Exp $ |
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28 | // GEANT4 tag $Name: hadr-chips-V09-03-08 $ |
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29 | // |
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30 | // Created by Mikhail Kosov 6-Nov-2009 |
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31 | // |
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32 | // -------------------------------------------------------------- |
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33 | // Short description: Algorithm of Synchrotron Radiation from PDG |
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34 | // gamma>>1: dI/dw=(8pi/9)*alpha*gamma*F(w/wc), wc=3*gamma^3*c/2/R |
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35 | // F(y)=(9*sqrt(3)/8/pi)*y*int{y,inf}(K_(5/3)(x)dx) (approximated) |
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36 | // N_gamma=[5pi/sqrt(3)]*alpha*gamma; <w>=[8/15/sqrt(3)]*wc |
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37 | // for electrons/positrons: wc(keV)=2.22*[E(GeV)]^3/R(m) |
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38 | // dE per revolution = (4pi/3)*e^2*beta^3*gamma/R |
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39 | // at beta=1, dE(MeV)=.o885*[E(GeV)]^4/R(m) |
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40 | //--------------------------------------------------------------- |
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41 | |
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42 | //#define debug |
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43 | //#define pdebug |
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44 | |
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45 | #include "G4QSynchRad.hh" |
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46 | |
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47 | // Constructor |
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48 | G4QSynchRad::G4QSynchRad(const G4String& Name, G4ProcessType Type): |
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49 | G4VDiscreteProcess (Name, Type), minGamma(227.), Polarization(0.,0.,1.) {} |
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50 | |
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51 | // Calculates MeanFreePath in GEANT4 internal units |
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52 | G4double G4QSynchRad::GetMeanFreePath(const G4Track& track,G4double,G4ForceCondition* cond) |
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53 | { |
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54 | static const G4double coef = 0.4*std::sqrt(3.)/fine_structure_const; |
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55 | const G4DynamicParticle* particle = track.GetDynamicParticle(); |
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56 | *cond = NotForced ; |
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57 | G4double gamma = particle->GetTotalEnergy() / particle->GetMass(); |
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58 | #ifdef debug |
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59 | G4cout<<"G4QSynchRad::MeanFreePath: gamma = "<<gamma<<G4endl; |
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60 | #endif |
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61 | G4double MFP = DBL_MAX; |
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62 | if( gamma > minGamma ) // For smalle gamma neglect the process |
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63 | { |
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64 | G4double R = GetRadius(track); |
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65 | #ifdef debug |
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66 | G4cout<<"G4QSynchRad::MeanFreePath: Radius = "<<R/meter<<" [m]"<<G4endl; |
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67 | #endif |
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68 | if(R > 0.) MFP= coef*R/gamma; |
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69 | } |
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70 | #ifdef debug |
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71 | G4cout<<"G4QSynchRad::MeanFreePath = "<<MFP/centimeter<<" [cm]"<<G4endl; |
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72 | #endif |
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73 | return MFP; |
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74 | } |
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75 | |
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76 | G4VParticleChange* G4QSynchRad::PostStepDoIt(const G4Track& track, const G4Step& step) |
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77 | |
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78 | { |
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79 | static const G4double hc = 1.5 * c_light * hbar_Planck; // E_c=h*w_c=1.5*(hc)*(gamma^3)/R |
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80 | aParticleChange.Initialize(track); |
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81 | const G4DynamicParticle* particle=track.GetDynamicParticle(); |
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82 | G4double gamma = particle->GetTotalEnergy() / particle->GetMass(); |
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83 | if(gamma <= minGamma ) |
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84 | { |
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85 | #ifdef debug |
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86 | G4cout<<"-Warning-G4QSynchRad::PostStepDoIt is called for small gamma="<<gamma<<G4endl; |
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87 | #endif |
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88 | return G4VDiscreteProcess::PostStepDoIt(track,step); |
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89 | } |
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90 | // Photon energy calculation (E < 8.1*Ec restriction) |
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91 | G4double R = GetRadius(track); |
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92 | if(R <= 0.) |
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93 | { |
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94 | #ifdef debug |
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95 | G4cout<<"-Warning-G4QSynchRad::PostStepDoIt: zero or negativ radius =" |
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96 | <<R/meter<<" [m]"<<G4endl; |
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97 | #endif |
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98 | return G4VDiscreteProcess::PostStepDoIt(track, step); |
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99 | } |
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100 | G4double EPhoton = hc * gamma * gamma * gamma / R; // E_c |
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101 | G4double dd=5.e-8; |
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102 | G4double rnd=G4UniformRand()*(1.+dd); |
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103 | if (rnd < 0.5 ) EPhoton *= .65 * rnd * rnd * rnd; |
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104 | else if(rnd > .997) EPhoton *= 15.-1.03*std::log((1.-rnd)/dd+1.); |
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105 | else |
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106 | { |
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107 | G4double r2=rnd*rnd; |
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108 | G4double dr=1.-rnd; |
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109 | EPhoton*=(2806.+28./rnd)/(1.+500./r2/r2+6500.*(std::sqrt(dr)+28.*dr*dr*dr)); |
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110 | } |
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111 | #ifdef debug |
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112 | G4cout<<"G4SynchRad::PostStepDoIt: PhotonEnergy = "<<EPhoton/keV<<" [keV]"<<G4endl; |
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113 | #endif |
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114 | if(EPhoton <= 0.) |
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115 | { |
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116 | G4cout<<"-Warning-G4QSynchRad::PostStepDoIt: zero or negativ photon energy=" |
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117 | <<EPhoton/keV<<" [keV]"<<G4endl; |
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118 | return G4VDiscreteProcess::PostStepDoIt(track, step); |
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119 | } |
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120 | G4double kinEn = particle->GetKineticEnergy(); |
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121 | G4double newEn = kinEn - EPhoton ; |
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122 | if (newEn > 0.) |
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123 | { |
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124 | aParticleChange.ProposeEnergy(newEn); |
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125 | aParticleChange.ProposeLocalEnergyDeposit (0.); |
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126 | } |
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127 | else // Very low probable event |
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128 | { |
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129 | G4cout<<"-Warning-G4QSynchRad::PostStepDoIt: PhotonEnergy > TotalKinEnergy"<<G4endl; |
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130 | EPhoton = kinEn; |
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131 | aParticleChange.ProposeEnergy(0.); |
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132 | aParticleChange.ProposeLocalEnergyDeposit(0.); |
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133 | aParticleChange.ProposeTrackStatus(fStopButAlive) ; |
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134 | } |
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135 | G4ThreeVector MomDir = particle->GetMomentumDirection(); |
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136 | G4DynamicParticle* Photon = new G4DynamicParticle(G4Gamma::Gamma(), MomDir, EPhoton); |
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137 | Photon->SetPolarization(Polarization.x(), Polarization.y(), Polarization.z()); |
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138 | aParticleChange.SetNumberOfSecondaries(1); |
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139 | aParticleChange.AddSecondary(Photon); |
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140 | return G4VDiscreteProcess::PostStepDoIt(track,step); |
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141 | } |
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142 | |
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143 | // Revolution Radius in independent units for the particle (general member function) |
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144 | G4double G4QSynchRad::GetRadius(const G4Track& track) |
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145 | { |
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146 | static const G4double unk = meter*tesla/0.3/gigaelectronvolt; |
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147 | const G4DynamicParticle* particle = track.GetDynamicParticle(); |
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148 | G4double z = particle->GetDefinition()->GetPDGCharge(); |
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149 | if(z == 0.) return 0.; // --> neutral particle |
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150 | if(z < 0.) z=-z; |
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151 | G4TransportationManager* transMan = G4TransportationManager::GetTransportationManager(); |
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152 | G4PropagatorInField* Field = transMan->GetPropagatorInField(); |
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153 | G4FieldManager* fMan = Field->FindAndSetFieldManager(track.GetVolume()); |
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154 | if(!fMan || !fMan->GetDetectorField()) return 0.; // --> no field at all |
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155 | const G4Field* pField = fMan->GetDetectorField(); |
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156 | G4ThreeVector position = track.GetPosition(); |
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157 | G4double PosArray[3]={position.x(), position.y(), position.z()}; |
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158 | G4double BArray[3]; |
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159 | pField->GetFieldValue(PosArray, BArray); |
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160 | G4ThreeVector B3D(BArray[0], BArray[1], BArray[2]); |
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161 | #ifdef debug |
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162 | G4cout<<"G4QSynchRad::GetRadius: Pos="<<position/meter<<", B(tesla)="<<B3D/tesla<<G4endl; |
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163 | #endif |
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164 | G4ThreeVector MomDir = particle->GetMomentumDirection(); |
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165 | G4ThreeVector Ort = B3D.cross(MomDir); |
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166 | G4double OrtB = Ort.mag(); // not negative (independent units) |
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167 | if(OrtB == 0.) return 0.; // --> along the field line |
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168 | Polarization = Ort/OrtB; // Polarization unit vector |
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169 | G4double mom = particle->GetTotalMomentum(); // Momentum of the particle |
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170 | #ifdef debug |
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171 | G4cout<<"G4QSynchRad::GetRadius: P(GeV)="<<mom/GeV<<", B(tesla)="<<OrtB/tesla<<G4endl; |
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172 | #endif |
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173 | // R [m]= mom [GeV]/(0.3 * z * OrtB [tesla]) |
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174 | return mom * unk / z / OrtB; |
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175 | } |
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