[819] | 1 | // |
---|
| 2 | // ******************************************************************** |
---|
| 3 | // * License and Disclaimer * |
---|
| 4 | // * * |
---|
| 5 | // * The Geant4 software is copyright of the Copyright Holders of * |
---|
| 6 | // * the Geant4 Collaboration. It is provided under the terms and * |
---|
| 7 | // * conditions of the Geant4 Software License, included in the file * |
---|
| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
---|
| 9 | // * include a list of copyright holders. * |
---|
| 10 | // * * |
---|
| 11 | // * Neither the authors of this software system, nor their employing * |
---|
| 12 | // * institutes,nor the agencies providing financial support for this * |
---|
| 13 | // * work make any representation or warranty, express or implied, * |
---|
| 14 | // * regarding this software system or assume any liability for its * |
---|
| 15 | // * use. Please see the license in the file LICENSE and URL above * |
---|
| 16 | // * for the full disclaimer and the limitation of liability. * |
---|
| 17 | // * * |
---|
| 18 | // * This code implementation is the result of the scientific and * |
---|
| 19 | // * technical work of the GEANT4 collaboration. * |
---|
| 20 | // * By using, copying, modifying or distributing the software (or * |
---|
| 21 | // * any work based on the software) you agree to acknowledge its * |
---|
| 22 | // * use in resulting scientific publications, and indicate your * |
---|
| 23 | // * acceptance of all terms of the Geant4 Software license. * |
---|
| 24 | // ******************************************************************** |
---|
| 25 | // |
---|
| 26 | // |
---|
| 27 | // $Id: G4PolarizedComptonScattering.cc,v 1.16 2006/06/29 19:53:30 gunter Exp $ |
---|
| 28 | // GEANT4 tag $Name: geant4-09-01-patch-02 $ |
---|
| 29 | // |
---|
| 30 | // |
---|
| 31 | //---------- G4PolarizedComptonScattering physics process ---------------------- |
---|
| 32 | // by Vicente Lara, March 1998 |
---|
| 33 | // |
---|
| 34 | // ----------------------------------------------------------------------------- |
---|
| 35 | // Corrections by Rui Curado da Silva (Nov. 2000) |
---|
| 36 | // - Sampling of Phi |
---|
| 37 | // - Depolarization probability |
---|
| 38 | // |
---|
| 39 | // 13-07-01, DoIt: suppression of production cut for the electron (mma) |
---|
| 40 | // 20-09-01, DoIt: fminimalEnergy = 1*eV (mma) |
---|
| 41 | // 04-05-05, Inheritance from ComptonScattering52 (V.Ivanchenko) |
---|
| 42 | // 30-01-06, DoIt : return G4ComptonScattering52::PostStepDoIt(aTrack,aStep) mma |
---|
| 43 | // |
---|
| 44 | // ----------------------------------------------------------------------------- |
---|
| 45 | |
---|
| 46 | #include "G4PolarizedComptonScattering.hh" |
---|
| 47 | |
---|
| 48 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 49 | |
---|
| 50 | using namespace std; |
---|
| 51 | |
---|
| 52 | G4PolarizedComptonScattering::G4PolarizedComptonScattering( |
---|
| 53 | const G4String& processName) |
---|
| 54 | : G4ComptonScattering52 (processName) |
---|
| 55 | { } |
---|
| 56 | |
---|
| 57 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 58 | |
---|
| 59 | G4VParticleChange* G4PolarizedComptonScattering::PostStepDoIt( |
---|
| 60 | const G4Track& aTrack, |
---|
| 61 | const G4Step& aStep) |
---|
| 62 | // |
---|
| 63 | // The scattered gamma energy is sampled according to Klein - Nishina formula. |
---|
| 64 | // The random number techniques of Butcher & Messel are used |
---|
| 65 | // (Nuc Phys 20(1960),15). |
---|
| 66 | // GEANT4 internal units |
---|
| 67 | // |
---|
| 68 | // Note : Effects due to binding of atomic electrons are negliged. |
---|
| 69 | |
---|
| 70 | { |
---|
| 71 | aParticleChange.Initialize(aTrack); |
---|
| 72 | |
---|
| 73 | const G4DynamicParticle* aDynamicGamma = aTrack.GetDynamicParticle(); |
---|
| 74 | |
---|
| 75 | G4ThreeVector GammaPolarization0 = aDynamicGamma->GetPolarization(); |
---|
| 76 | |
---|
| 77 | if (std::abs(GammaPolarization0.mag() - 1.e0) > 1.e-14) |
---|
| 78 | return G4ComptonScattering52::PostStepDoIt(aTrack,aStep); |
---|
| 79 | |
---|
| 80 | G4double GammaEnergy0 = aDynamicGamma->GetKineticEnergy(); |
---|
| 81 | G4double E0_m = GammaEnergy0 / electron_mass_c2; |
---|
| 82 | |
---|
| 83 | G4ParticleMomentum GammaDirection0 = aDynamicGamma->GetMomentumDirection(); |
---|
| 84 | |
---|
| 85 | // |
---|
| 86 | // sample the energy rate of the scattered gamma |
---|
| 87 | // |
---|
| 88 | G4double epsilon, epsilonsq, onecost, sint2, greject; |
---|
| 89 | |
---|
| 90 | G4double epsilon0 = 1./(1. + 2*E0_m) , epsilon0sq = epsilon0*epsilon0; |
---|
| 91 | G4double alpha1 = - log(epsilon0) , alpha2 = 0.5*(1.- epsilon0sq); |
---|
| 92 | |
---|
| 93 | do { |
---|
| 94 | if (alpha1/(alpha1+alpha2) > G4UniformRand()) |
---|
| 95 | { epsilon = exp(-alpha1*G4UniformRand()); // epsilon0**r |
---|
| 96 | epsilonsq = epsilon*epsilon; } |
---|
| 97 | else { |
---|
| 98 | epsilonsq = epsilon0sq + (1.- epsilon0sq)*G4UniformRand(); |
---|
| 99 | epsilon = sqrt(epsilonsq); |
---|
| 100 | }; |
---|
| 101 | onecost = (1.- epsilon)/(epsilon*E0_m); |
---|
| 102 | sint2 = onecost*(2.-onecost); |
---|
| 103 | greject = 1. - epsilon*sint2/(1.+ epsilonsq); |
---|
| 104 | } while (greject < G4UniformRand()); |
---|
| 105 | |
---|
| 106 | |
---|
| 107 | // |
---|
| 108 | // Phi determination |
---|
| 109 | // |
---|
| 110 | G4double minimum=0., maximum=twopi, middle=0., resolution=0.001; |
---|
| 111 | G4double Rand = G4UniformRand(); |
---|
| 112 | |
---|
| 113 | int j = 0; |
---|
| 114 | while ((j < 100) && (std::abs(SetPhi(epsilon,sint2,middle,Rand)) > resolution)) |
---|
| 115 | { |
---|
| 116 | middle = (maximum + minimum)/2; |
---|
| 117 | if (SetPhi(epsilon,sint2,middle,Rand)* |
---|
| 118 | SetPhi(epsilon,sint2,minimum,Rand)<0) maximum = middle; |
---|
| 119 | else minimum = middle; |
---|
| 120 | j++; |
---|
| 121 | } |
---|
| 122 | |
---|
| 123 | // |
---|
| 124 | // scattered gamma angles. ( Z - axis along the parent gamma) |
---|
| 125 | // |
---|
| 126 | G4double cosTeta = 1. - onecost , sinTeta = sqrt (sint2); |
---|
| 127 | G4double Phi = middle; |
---|
| 128 | G4double dirx = sinTeta*cos(Phi), diry = sinTeta*sin(Phi), dirz = cosTeta; |
---|
| 129 | |
---|
| 130 | // |
---|
| 131 | // update G4VParticleChange for the scattered gamma |
---|
| 132 | // |
---|
| 133 | G4double GammaEnergy1 = epsilon*GammaEnergy0; |
---|
| 134 | |
---|
| 135 | // New polarization |
---|
| 136 | // |
---|
| 137 | G4ThreeVector GammaPolarization1 = SetNewPolarization(epsilon,sint2,Phi, |
---|
| 138 | cosTeta, |
---|
| 139 | GammaPolarization0); |
---|
| 140 | // Set new direction |
---|
| 141 | G4ThreeVector GammaDirection1 ( dirx,diry,dirz ); |
---|
| 142 | |
---|
| 143 | // Change reference frame. |
---|
| 144 | SystemOfRefChange(GammaDirection0,GammaDirection1, |
---|
| 145 | GammaPolarization0,GammaPolarization1); |
---|
| 146 | |
---|
| 147 | G4double localEnergyDeposit = 0.; |
---|
| 148 | |
---|
| 149 | if (GammaEnergy1 > fminimalEnergy) |
---|
| 150 | { |
---|
| 151 | aParticleChange.ProposeEnergy(GammaEnergy1); |
---|
| 152 | } |
---|
| 153 | else |
---|
| 154 | { |
---|
| 155 | localEnergyDeposit += GammaEnergy1; |
---|
| 156 | aParticleChange.ProposeEnergy(0.) ; |
---|
| 157 | aParticleChange.ProposeTrackStatus(fStopAndKill); |
---|
| 158 | } |
---|
| 159 | |
---|
| 160 | // |
---|
| 161 | // kinematic of the scattered electron |
---|
| 162 | // |
---|
| 163 | G4double ElecKineEnergy = GammaEnergy0 - GammaEnergy1; |
---|
| 164 | |
---|
| 165 | if (ElecKineEnergy > fminimalEnergy) |
---|
| 166 | { |
---|
| 167 | G4double ElecMomentum = sqrt(ElecKineEnergy* |
---|
| 168 | (ElecKineEnergy+2.*electron_mass_c2)); |
---|
| 169 | G4ThreeVector ElecDirection ( |
---|
| 170 | (GammaEnergy0*GammaDirection0 - GammaEnergy1*GammaDirection1) |
---|
| 171 | *(1./ElecMomentum)); |
---|
| 172 | |
---|
| 173 | // create G4DynamicParticle object for the electron. |
---|
| 174 | G4DynamicParticle* aElectron= new G4DynamicParticle ( |
---|
| 175 | G4Electron::Electron(),ElecDirection,ElecKineEnergy); |
---|
| 176 | aParticleChange.SetNumberOfSecondaries(1); |
---|
| 177 | aParticleChange.AddSecondary( aElectron ); |
---|
| 178 | } |
---|
| 179 | else |
---|
| 180 | { |
---|
| 181 | aParticleChange.SetNumberOfSecondaries(0); |
---|
| 182 | localEnergyDeposit += ElecKineEnergy; |
---|
| 183 | } |
---|
| 184 | |
---|
| 185 | aParticleChange.ProposeLocalEnergyDeposit(localEnergyDeposit); |
---|
| 186 | |
---|
| 187 | // Reset NbOfInteractionLengthLeft and return aParticleChange |
---|
| 188 | return G4VDiscreteProcess::PostStepDoIt( aTrack, aStep); |
---|
| 189 | } |
---|
| 190 | |
---|
| 191 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 192 | |
---|
| 193 | G4double G4PolarizedComptonScattering::SetPhi(G4double EnergyRate, |
---|
| 194 | G4double sinsqrth, |
---|
| 195 | G4double phi, |
---|
| 196 | G4double rand) |
---|
| 197 | { |
---|
| 198 | G4double cosphi = cos(phi), sinphi = sin(phi); |
---|
| 199 | G4double PhiDetermination = ((twopi*rand - phi) |
---|
| 200 | *(EnergyRate + 1./EnergyRate - sinsqrth)) |
---|
| 201 | + (sinsqrth*sinphi*cosphi); |
---|
| 202 | return PhiDetermination; |
---|
| 203 | } |
---|
| 204 | |
---|
| 205 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 206 | |
---|
| 207 | G4ThreeVector G4PolarizedComptonScattering::SetNewPolarization( |
---|
| 208 | G4double EnergyRate, |
---|
| 209 | G4double sinsqrth, |
---|
| 210 | G4double phi, |
---|
| 211 | G4double costheta, |
---|
| 212 | G4ThreeVector&) |
---|
| 213 | { |
---|
| 214 | G4double cosphi = cos(phi), sinphi = sin(phi); |
---|
| 215 | //// G4double ParallelIntensityPolar = EnergyRate + 1./EnergyRate |
---|
| 216 | //// + 2. - 4.*sinsqrth*cosphi*cosphi; |
---|
| 217 | G4double ParallelIntensityPolar = EnergyRate + 1./EnergyRate |
---|
| 218 | - 2.*sinsqrth*cosphi*cosphi; |
---|
| 219 | G4double PerpendiIntensityPolar = EnergyRate + 1./EnergyRate - 2.; |
---|
| 220 | G4double PolarizationDegree = sqrt(sinsqrth*sinphi*sinphi+costheta*costheta); |
---|
| 221 | G4double sintheta = sqrt(sinsqrth); |
---|
| 222 | |
---|
| 223 | G4ThreeVector GammaPolarization1; |
---|
| 224 | // depolarization probability (1-P) |
---|
| 225 | if ( G4UniformRand() > (PerpendiIntensityPolar/ParallelIntensityPolar) ) |
---|
| 226 | { |
---|
| 227 | // Parallel to initial polarization |
---|
| 228 | GammaPolarization1.setX(PolarizationDegree); |
---|
| 229 | GammaPolarization1.setY(-sinsqrth*sinphi*cosphi/PolarizationDegree); |
---|
| 230 | GammaPolarization1.setZ(-sintheta*costheta*cosphi/PolarizationDegree); |
---|
| 231 | |
---|
| 232 | } |
---|
| 233 | else |
---|
| 234 | { |
---|
| 235 | // Perpendicular to initial polarization |
---|
| 236 | GammaPolarization1.setX(0.); |
---|
| 237 | GammaPolarization1.setY(costheta/PolarizationDegree); |
---|
| 238 | GammaPolarization1.setZ(-sintheta*sinphi/PolarizationDegree); |
---|
| 239 | |
---|
| 240 | }; |
---|
| 241 | |
---|
| 242 | return GammaPolarization1; |
---|
| 243 | } |
---|
| 244 | |
---|
| 245 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|
| 246 | |
---|
| 247 | void G4PolarizedComptonScattering::SystemOfRefChange(G4ThreeVector& Direction0, |
---|
| 248 | G4ThreeVector& Direction1, |
---|
| 249 | G4ThreeVector& Polarization0, |
---|
| 250 | G4ThreeVector& Polarization1) |
---|
| 251 | { |
---|
| 252 | // Angles for go back to the original RS |
---|
| 253 | G4double cosTeta0 = Direction0.cosTheta(), sinTeta0 = sin(Direction0.theta()); |
---|
| 254 | G4double cosPhi0 = cos(Direction0.phi()), sinPhi0 = sin(Direction0.phi()); |
---|
| 255 | |
---|
| 256 | |
---|
| 257 | |
---|
| 258 | G4double cosPsi, sinPsi; |
---|
| 259 | |
---|
| 260 | if (sinTeta0 != 0. ) |
---|
| 261 | { |
---|
| 262 | cosPsi = -Polarization0.z()/sinTeta0; |
---|
| 263 | if (cosPhi0 != 0.) |
---|
| 264 | sinPsi = (Polarization0.y() - cosTeta0*sinPhi0*cosPsi)/cosPhi0; |
---|
| 265 | else sinPsi = -Polarization0.x()/sinPhi0; |
---|
| 266 | |
---|
| 267 | } |
---|
| 268 | else |
---|
| 269 | { |
---|
| 270 | cosPsi = Polarization0.x()/cosTeta0; |
---|
| 271 | sinPsi = Polarization0.y(); |
---|
| 272 | } |
---|
| 273 | G4double Psi = atan(sinPsi/cosPsi); |
---|
| 274 | |
---|
| 275 | // Rotation along Z axe |
---|
| 276 | Direction1.rotateZ(Psi); |
---|
| 277 | // |
---|
| 278 | Direction1.rotateUz(Direction0); |
---|
| 279 | aParticleChange.ProposeMomentumDirection(Direction1); |
---|
| 280 | |
---|
| 281 | // 3 Euler angles rotation for scattered photon polarization |
---|
| 282 | Polarization1.rotateZ(Psi); |
---|
| 283 | Polarization1.rotateUz(Direction0); |
---|
| 284 | aParticleChange.ProposePolarization(Polarization1); |
---|
| 285 | |
---|
| 286 | } |
---|
| 287 | |
---|
| 288 | //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... |
---|