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64 { << 68 65 G4Mutex theBetheHMutex = G4MUTEX_INITIALIZER << 69 static const G4double GammaEnergyLimit = 1.5*MeV; 66 } << 70 static const G4double Egsmall=2.*MeV; >> 71 static const G4double >> 72 a0= 8.7842e+2*microbarn, a1=-1.9625e+3*microbarn, a2= 1.2949e+3*microbarn, >> 73 a3=-2.0028e+2*microbarn, a4= 1.2575e+1*microbarn, a5=-2.8333e-1*microbarn; >> 74 >> 75 static const G4double >> 76 b0=-1.0342e+1*microbarn, b1= 1.7692e+1*microbarn, b2=-8.2381 *microbarn, >> 77 b3= 1.3063 *microbarn, b4=-9.0815e-2*microbarn, b5= 2.3586e-3*microbarn; >> 78 >> 79 static const G4double >> 80 c0=-4.5263e+2*microbarn, c1= 1.1161e+3*microbarn, c2=-8.6749e+2*microbarn, >> 81 c3= 2.1773e+2*microbarn, c4=-2.0467e+1*microbarn, c5= 6.5372e-1*microbarn; 67 82 68 G4BetheHeitlerModel::G4BetheHeitlerModel(const << 83 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... 69 const << 84 70 : G4VEmModel(nam), << 85 G4BetheHeitlerModel::G4BetheHeitlerModel(const G4ParticleDefinition*, 71 fG4Calc(G4Pow::GetInstance()), fTheGamma(G4G << 86 const G4String& nam) 72 fTheElectron(G4Electron::Electron()), fThePo << 87 : G4VEmModel(nam) 73 fParticleChange(nullptr) << 74 { 88 { 75 SetAngularDistribution(new G4ModifiedTsai()) << 89 fParticleChange = 0; >> 90 theGamma = G4Gamma::Gamma(); >> 91 thePositron = G4Positron::Positron(); >> 92 theElectron = G4Electron::Electron(); >> 93 g4pow = G4Pow::GetInstance(); 76 } 94 } 77 95 >> 96 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... >> 97 78 G4BetheHeitlerModel::~G4BetheHeitlerModel() 98 G4BetheHeitlerModel::~G4BetheHeitlerModel() 79 { << 99 {} 80 if (isFirstInstance) { << 81 for (auto const & ptr : gElementData) { de << 82 gElementData.clear(); << 83 } << 84 delete fXSection; << 85 } << 86 100 87 void G4BetheHeitlerModel::Initialise(const G4P << 101 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... 88 const G4D << 89 { << 90 if (!fParticleChange) { fParticleChange = Ge << 91 102 92 if (isFirstInstance || gElementData.empty()) << 103 void G4BetheHeitlerModel::Initialise(const G4ParticleDefinition* p, 93 G4AutoLock l(&theBetheHMutex); << 104 const G4DataVector& cuts) 94 if (gElementData.empty()) { << 105 { 95 isFirstInstance = true; << 106 if(!fParticleChange) { fParticleChange = GetParticleChangeForGamma(); } 96 gElementData.resize(gMaxZet+1, nullptr); << 107 if(IsMaster()) { InitialiseElementSelectors(p, cuts); } 97 << 98 // EPICS2017 flag should be checked only << 99 useEPICS2017 = G4EmParameters::Instance( << 100 if (useEPICS2017) { << 101 fXSection = new G4EmElementXS(1, 100, "convE << 102 } << 103 } << 104 // static data should be initialised only << 105 InitialiseElementData(); << 106 l.unlock(); << 107 } << 108 // element selectors should be initialised i << 109 if(IsMaster()) { << 110 InitialiseElementSelectors(p, cuts); << 111 } << 112 } 108 } 113 109 114 void G4BetheHeitlerModel::InitialiseLocal(cons << 110 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... 115 G4VE << 111 >> 112 void G4BetheHeitlerModel::InitialiseLocal(const G4ParticleDefinition*, >> 113 G4VEmModel* masterModel) 116 { 114 { 117 SetElementSelectors(masterModel->GetElementS 115 SetElementSelectors(masterModel->GetElementSelectors()); 118 } 116 } 119 117 >> 118 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... >> 119 >> 120 G4double >> 121 G4BetheHeitlerModel::ComputeCrossSectionPerAtom(const G4ParticleDefinition*, >> 122 G4double GammaEnergy, G4double Z, >> 123 G4double, G4double, G4double) 120 // Calculates the microscopic cross section in 124 // Calculates the microscopic cross section in GEANT4 internal units. 121 // A parametrized formula from L. Urban is use 125 // A parametrized formula from L. Urban is used to estimate 122 // the total cross section. 126 // the total cross section. 123 // It gives a good description of the data fro 127 // It gives a good description of the data from 1.5 MeV to 100 GeV. 124 // below 1.5 MeV: sigma=sigma(1.5MeV)*(GammaEn 128 // below 1.5 MeV: sigma=sigma(1.5MeV)*(GammaEnergy-2electronmass) 125 // *(GammaEn 129 // *(GammaEnergy-2electronmass) 126 G4double << 127 G4BetheHeitlerModel::ComputeCrossSectionPerAto << 128 << 129 << 130 { 130 { 131 G4double xSection = 0.0 ; 131 G4double xSection = 0.0 ; 132 // short versions << 132 if ( Z < 0.9 || GammaEnergy <= 2.0*electron_mass_c2 ) { return xSection; } 133 static const G4double kMC2 = CLHEP::electro << 133 134 // zero cross section below the kinematical << 134 135 if (Z < 0.9 || gammaEnergy <= 2.0*kMC2) { re << 135 G4double GammaEnergySave = GammaEnergy; 136 << 136 if (GammaEnergy < GammaEnergyLimit) { GammaEnergy = GammaEnergyLimit; } 137 G4int iZ = G4lrint(Z); << 137 138 if (useEPICS2017 && iZ < 101) { << 138 G4double X=G4Log(GammaEnergy/electron_mass_c2), X2=X*X, X3=X2*X, X4=X3*X, X5=X4*X; 139 return fXSection->GetXS(iZ, gammaEnergy); << 139 140 } << 140 G4double F1 = a0 + a1*X + a2*X2 + a3*X3 + a4*X4 + a5*X5, >> 141 F2 = b0 + b1*X + b2*X2 + b3*X3 + b4*X4 + b5*X5, >> 142 F3 = c0 + c1*X + c2*X2 + c3*X3 + c4*X4 + c5*X5; 141 143 142 // << 143 static const G4double gammaEnergyLimit = 1.5 << 144 // set coefficients a, b c << 145 static const G4double a0 = 8.7842e+2*CLHEP: << 146 static const G4double a1 = -1.9625e+3*CLHEP: << 147 static const G4double a2 = 1.2949e+3*CLHEP: << 148 static const G4double a3 = -2.0028e+2*CLHEP: << 149 static const G4double a4 = 1.2575e+1*CLHEP: << 150 static const G4double a5 = -2.8333e-1*CLHEP: << 151 << 152 static const G4double b0 = -1.0342e+1*CLHEP: << 153 static const G4double b1 = 1.7692e+1*CLHEP: << 154 static const G4double b2 = -8.2381 *CLHEP: << 155 static const G4double b3 = 1.3063 *CLHEP: << 156 static const G4double b4 = -9.0815e-2*CLHEP: << 157 static const G4double b5 = 2.3586e-3*CLHEP: << 158 << 159 static const G4double c0 = -4.5263e+2*CLHEP: << 160 static const G4double c1 = 1.1161e+3*CLHEP: << 161 static const G4double c2 = -8.6749e+2*CLHEP: << 162 static const G4double c3 = 2.1773e+2*CLHEP: << 163 static const G4double c4 = -2.0467e+1*CLHEP: << 164 static const G4double c5 = 6.5372e-1*CLHEP: << 165 // check low energy limit of the approximati << 166 G4double gammaEnergyOrg = gammaEnergy; << 167 if (gammaEnergy < gammaEnergyLimit) { gammaE << 168 // compute gamma energy variables << 169 const G4double x = G4Log(gammaEnergy/kMC2); << 170 const G4double x2 = x *x; << 171 const G4double x3 = x2*x; << 172 const G4double x4 = x3*x; << 173 const G4double x5 = x4*x; << 174 // << 175 const G4double F1 = a0 + a1*x + a2*x2 + a3*x << 176 const G4double F2 = b0 + b1*x + b2*x2 + b3*x << 177 const G4double F3 = c0 + c1*x + c2*x2 + c3*x << 178 // compute the approximated cross section << 179 xSection = (Z + 1.)*(F1*Z + F2*Z*Z + F3); 144 xSection = (Z + 1.)*(F1*Z + F2*Z*Z + F3); 180 // check if we are below the limit of the ap << 145 181 if (gammaEnergyOrg < gammaEnergyLimit) { << 146 if (GammaEnergySave < GammaEnergyLimit) { 182 const G4double dum = (gammaEnergyOrg-2.*kM << 147 183 xSection *= dum*dum; << 148 X = (GammaEnergySave - 2.*electron_mass_c2) >> 149 / (GammaEnergyLimit - 2.*electron_mass_c2); >> 150 xSection *= X*X; 184 } 151 } 185 // make sure that the cross section is never << 152 186 xSection = std::max(xSection, 0.); << 153 if (xSection < 0.) { xSection = 0.; } 187 return xSection; 154 return xSection; 188 } 155 } 189 156 >> 157 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.... >> 158 >> 159 void G4BetheHeitlerModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect, >> 160 const G4MaterialCutsCouple* couple, >> 161 const G4DynamicParticle* aDynamicGamma, >> 162 G4double, >> 163 G4double) 190 // The secondaries e+e- energies are sampled u 164 // The secondaries e+e- energies are sampled using the Bethe - Heitler 191 // cross sections with Coulomb correction. 165 // cross sections with Coulomb correction. 192 // A modified version of the random number tec 166 // A modified version of the random number techniques of Butcher & Messel 193 // is used (Nuc Phys 20(1960),15). 167 // is used (Nuc Phys 20(1960),15). 194 // 168 // 195 // GEANT4 internal units. 169 // GEANT4 internal units. 196 // 170 // 197 // Note 1 : Effects due to the breakdown of th 171 // Note 1 : Effects due to the breakdown of the Born approximation at 198 // low energy are ignored. 172 // low energy are ignored. 199 // Note 2 : The differential cross section imp 173 // Note 2 : The differential cross section implicitly takes account of 200 // pair creation in both nuclear and 174 // pair creation in both nuclear and atomic electron fields. 201 // However triplet prodution is not g 175 // However triplet prodution is not generated. 202 void G4BetheHeitlerModel::SampleSecondaries(st << 203 co << 204 co << 205 G4 << 206 { 176 { 207 // set some constant values << 177 const G4Material* aMaterial = couple->GetMaterial(); 208 const G4double gammaEnergy = aDynamicGamm << 178 209 const G4double eps0 = CLHEP::elect << 179 G4double GammaEnergy = aDynamicGamma->GetKineticEnergy(); 210 // << 180 G4ParticleMomentum GammaDirection = aDynamicGamma->GetMomentumDirection(); 211 // check kinematical limit: gamma energy(Eg) << 181 212 if (eps0 > 0.5) { return; } << 182 G4double epsil ; 213 // << 183 G4double epsil0 = electron_mass_c2/GammaEnergy ; 214 // select target element of the material (pr << 184 if(epsil0 > 1.0) { return; } 215 const G4Element* anElement = SelectTargetAto << 185 216 aDyn << 186 // do it fast if GammaEnergy < Egsmall 217 << 187 // select randomly one element constituing the material 218 // << 188 const G4Element* anElement = SelectRandomAtom(aMaterial, theGamma, GammaEnergy); 219 // get the random engine << 189 220 CLHEP::HepRandomEngine* rndmEngine = G4Rando << 190 if (GammaEnergy < Egsmall) { 221 // << 191 222 // 'eps' is the total energy transferred to << 192 epsil = epsil0 + (0.5-epsil0)*G4UniformRand(); 223 // gamma energy units Eg. Since the correspo << 193 224 // the kinematical limits for eps0=mc^2/Eg < << 225 // 1. 'eps' is sampled uniformly on the [eps << 226 // 2. otherwise, on the [eps_min, 0.5] inter << 227 G4double eps; << 228 // case 1. << 229 static const G4double Egsmall = 2.*CLHEP::Me << 230 if (gammaEnergy < Egsmall) { << 231 eps = eps0 + (0.5-eps0)*rndmEngine->flat() << 232 } else { 194 } else { 233 // case 2. << 195 // now comes the case with GammaEnergy >= 2. MeV 234 // get the Coulomb factor for the target e << 196 235 // F(Z) = 8*ln(Z)/3 if Eg <= 50 << 197 // Extract Coulomb factor for this Element 236 // F(Z) = 8*ln(Z)/3 + 8*fc(Z) if Eg > 50 << 198 G4double FZ = 8.*(anElement->GetIonisation()->GetlogZ3()); >> 199 if (GammaEnergy > 50.*MeV) { FZ += 8.*(anElement->GetfCoulomb()); } >> 200 >> 201 // limits of the screening variable >> 202 G4double screenfac = 136.*epsil0/(anElement->GetIonisation()->GetZ3()); >> 203 G4double screenmax = exp ((42.24 - FZ)/8.368) - 0.952 ; >> 204 G4double screenmin = min(4.*screenfac,screenmax); >> 205 >> 206 // limits of the energy sampling >> 207 G4double epsil1 = 0.5 - 0.5*sqrt(1. - screenmin/screenmax) ; >> 208 G4double epsilmin = max(epsil0,epsil1) , epsilrange = 0.5 - epsilmin; >> 209 237 // 210 // 238 // The screening variable 'delta(eps)' = 1 << 211 // sample the energy rate of the created electron (or positron) 239 // Due to the Coulomb correction, the DCS << 240 // kinematicaly allowed eps > eps0 values. << 241 // range with negative DCS, the minimum ep << 242 // max[eps0, epsp] with epsp is the soluti << 243 // with SF being the screening function (S << 244 // The solution is epsp = 0.5 - 0.5*sqrt[ << 245 // with deltap = Exp[(42.038-F(Z))/8.29]-0 << 246 // - when eps=eps_max = 0.5 => << 247 // - epsp = 0.5 - 0.5*sqrt[ 1 - delta_min/ << 248 // - and eps_min = max[eps0, epsp] << 249 static const G4double midEnergy = 50.*CLHE << 250 const G4int iZet = std::min(gMa << 251 const G4double deltaFactor = 136.*eps0/an << 252 G4double deltaMax = gElementData << 253 G4double FZ = 8.*anElement << 254 if (gammaEnergy > midEnergy) { << 255 FZ += 8.*(anElement->GetfCoulomb()) << 256 deltaMax = gElementData[iZet]->fDeltaMax << 257 } << 258 const G4double deltaMin = 4.*deltaFactor; << 259 // << 260 // compute the limits of eps << 261 const G4double epsp = 0.5 - 0.5*std::s << 262 const G4double epsMin = std::max(eps0,ep << 263 const G4double epsRange = 0.5 - epsMin; << 264 // 212 // 265 // sample the energy rate (eps) of the cre << 213 //G4double epsil, screenvar, greject ; 266 G4double F10, F20; << 214 G4double screenvar, greject ; 267 ScreenFunction12(deltaMin, F10, F20); << 215 268 F10 -= FZ; << 216 G4double F10 = ScreenFunction1(screenmin) - FZ; 269 F20 -= FZ; << 217 G4double F20 = ScreenFunction2(screenmin) - FZ; 270 const G4double NormF1 = std::max(F10 * e << 218 G4double NormF1 = max(F10*epsilrange*epsilrange,0.); 271 const G4double NormF2 = std::max(1.5 * F << 219 G4double NormF2 = max(1.5*F20,0.); 272 const G4double NormCond = NormF1/(NormF1 + << 220 273 // we will need 3 uniform random number fo << 274 G4double rndmv[3]; << 275 G4double greject = 0.; << 276 do { 221 do { 277 rndmEngine->flatArray(3, rndmv); << 222 if ( NormF1/(NormF1+NormF2) > G4UniformRand() ) { 278 if (NormCond > rndmv[0]) { << 223 epsil = 0.5 - epsilrange*g4pow->A13(G4UniformRand()); 279 eps = 0.5 - epsRange * fG4Calc->A13(rn << 224 screenvar = screenfac/(epsil*(1-epsil)); 280 const G4double delta = deltaFactor/(ep << 225 greject = (ScreenFunction1(screenvar) - FZ)/F10; 281 greject = (ScreenFunction1(delta)-FZ)/ << 226 282 } else { 227 } else { 283 eps = epsMin + epsRange*rndmv[1]; << 228 epsil = epsilmin + epsilrange*G4UniformRand(); 284 const G4double delta = deltaFactor/(ep << 229 screenvar = screenfac/(epsil*(1-epsil)); 285 greject = (ScreenFunction2(delta)-FZ)/ << 230 greject = (ScreenFunction2(screenvar) - FZ)/F20; 286 } 231 } 287 // Loop checking, 03-Aug-2015, Vladimir << 232 288 } while (greject < rndmv[2]); << 233 } while( greject < G4UniformRand() ); 289 } // end of eps sampling << 234 >> 235 } // end of epsil sampling >> 236 290 // 237 // 291 // select charges randomly << 238 // fixe charges randomly 292 G4double eTotEnergy, pTotEnergy; << 239 // 293 if (rndmEngine->flat() > 0.5) { << 240 294 eTotEnergy = (1.-eps)*gammaEnergy; << 241 G4double ElectTotEnergy, PositTotEnergy; 295 pTotEnergy = eps*gammaEnergy; << 242 if (G4UniformRand() > 0.5) { >> 243 >> 244 ElectTotEnergy = (1.-epsil)*GammaEnergy; >> 245 PositTotEnergy = epsil*GammaEnergy; >> 246 296 } else { 247 } else { 297 pTotEnergy = (1.-eps)*gammaEnergy; << 248 298 eTotEnergy = eps*gammaEnergy; << 249 PositTotEnergy = (1.-epsil)*GammaEnergy; >> 250 ElectTotEnergy = epsil*GammaEnergy; 299 } 251 } >> 252 >> 253 // >> 254 // scattered electron (positron) angles. ( Z - axis along the parent photon) 300 // 255 // 301 // sample pair kinematics << 256 // universal distribution suggested by L. Urban 302 const G4double eKinEnergy = std::max(0.,eTot << 257 // (Geant3 manual (1993) Phys211), 303 const G4double pKinEnergy = std::max(0.,pTot << 258 // derived from Tsai distribution (Rev Mod Phys 49,421(1977)) >> 259 >> 260 G4double u; >> 261 static const G4double aa1 = 0.625; >> 262 static const G4double aa2 = 1.875; >> 263 static const G4double d = 27. ; >> 264 >> 265 if (9./(9.+d) >G4UniformRand()) u= - G4Log(G4UniformRand()*G4UniformRand())/aa1; >> 266 else u= - G4Log(G4UniformRand()*G4UniformRand())/aa2; >> 267 >> 268 G4double TetEl = u*electron_mass_c2/ElectTotEnergy; >> 269 G4double TetPo = u*electron_mass_c2/PositTotEnergy; >> 270 G4double Phi = twopi * G4UniformRand(); >> 271 G4double dxEl= sin(TetEl)*cos(Phi),dyEl= sin(TetEl)*sin(Phi),dzEl=cos(TetEl); >> 272 G4double dxPo=-sin(TetPo)*cos(Phi),dyPo=-sin(TetPo)*sin(Phi),dzPo=cos(TetPo); >> 273 304 // 274 // 305 G4ThreeVector eDirection, pDirection; << 275 // kinematic of the created pair 306 // 276 // 307 GetAngularDistribution()->SamplePairDirectio << 277 // the electron and positron are assumed to have a symetric 308 << 278 // angular distribution with respect to the Z axis along the parent photon. 309 << 279 310 // create G4DynamicParticle object for the p << 280 G4double ElectKineEnergy = max(0.,ElectTotEnergy - electron_mass_c2); 311 auto aParticle1= new G4DynamicParticle(fTheE << 281 312 // create G4DynamicParticle object for the p << 282 G4ThreeVector ElectDirection (dxEl, dyEl, dzEl); 313 auto aParticle2= new G4DynamicParticle(fTheP << 283 ElectDirection.rotateUz(GammaDirection); >> 284 >> 285 // create G4DynamicParticle object for the particle1 >> 286 G4DynamicParticle* aParticle1= new G4DynamicParticle( >> 287 theElectron,ElectDirection,ElectKineEnergy); >> 288 >> 289 // the e+ is always created (even with Ekine=0) for further annihilation. >> 290 >> 291 G4double PositKineEnergy = max(0.,PositTotEnergy - electron_mass_c2); >> 292 >> 293 G4ThreeVector PositDirection (dxPo, dyPo, dzPo); >> 294 PositDirection.rotateUz(GammaDirection); >> 295 >> 296 // create G4DynamicParticle object for the particle2 >> 297 G4DynamicParticle* aParticle2= new G4DynamicParticle( >> 298 thePositron,PositDirection,PositKineEnergy); >> 299 314 // Fill output vector 300 // Fill output vector 315 fvect->push_back(aParticle1); 301 fvect->push_back(aParticle1); 316 fvect->push_back(aParticle2); 302 fvect->push_back(aParticle2); >> 303 317 // kill incident photon 304 // kill incident photon 318 fParticleChange->SetProposedKineticEnergy(0. 305 fParticleChange->SetProposedKineticEnergy(0.); 319 fParticleChange->ProposeTrackStatus(fStopAnd 306 fParticleChange->ProposeTrackStatus(fStopAndKill); 320 } 307 } 321 308 322 // should be called only by the master and at << 309 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo...... 323 void G4BetheHeitlerModel::InitialiseElementDat << 324 { << 325 // create for all elements that are in the d << 326 auto elemTable = G4Element::GetElementTable( << 327 for (auto const & elem : *elemTable) { << 328 const G4int Z = elem->GetZasInt(); << 329 const G4int iz = std::min(gMaxZet, Z); << 330 if (nullptr == gElementData[iz]) { // crea << 331 G4double FZLow = 8.*elem->GetIonisat << 332 G4double FZHigh = FZLow + 8.*elem->Ge << 333 auto elD = new ElementData(); << 334 elD->fDeltaMaxLow = G4Exp((42.038 - FZL << 335 elD->fDeltaMaxHigh = G4Exp((42.038 - FZH << 336 gElementData[iz] = elD; << 337 } << 338 if (useEPICS2017 && Z < 101) { << 339 fXSection->Retrieve(Z); << 340 } << 341 } << 342 << 343 } << 344 << 345 310