Geant4 Cross Reference |
1 // 1 2 // ******************************************* 3 // * License and Disclaimer 4 // * 5 // * The Geant4 software is copyright of th 6 // * the Geant4 Collaboration. It is provided 7 // * conditions of the Geant4 Software License 8 // * LICENSE and available at http://cern.ch/ 9 // * include a list of copyright holders. 10 // * 11 // * Neither the authors of this software syst 12 // * institutes,nor the agencies providing fin 13 // * work make any representation or warran 14 // * regarding this software system or assum 15 // * use. Please see the license in the file 16 // * for the full disclaimer and the limitatio 17 // * 18 // * This code implementation is the result 19 // * technical work of the GEANT4 collaboratio 20 // * By using, copying, modifying or distri 21 // * any work based on the software) you ag 22 // * use in resulting scientific publicati 23 // * acceptance of all terms of the Geant4 Sof 24 // ******************************************* 25 // 26 // ------------------------------------------- 27 /// 28 // 29 // 30 // ------------------------------------------- 31 // 32 // Author: A. Forti 33 // Maria Grazia Pia (Maria.Grazia.Pia@ 34 // 35 // History: 36 // -------- 37 // 02/03/1999 A. Forti 1st implementation 38 // 14.03.2000 Veronique Lefebure; 39 // Change initialisation of lowestEnergyLimit 40 // Note that the hard coded value 1.022 should 41 // 2*electron_mass_c2 in order to agree with t 42 // 24.04.01 V.Ivanchenko remove RogueWave 43 // 27.07.01 F.Longo correct bug in energy dist 44 // 21.01.03 V.Ivanchenko Cut per region 45 // 25.03.03 F.Longo fix in angular distributio 46 // 24.04.03 V.Ivanchenko - Cut per region mfpt 47 // 48 // ------------------------------------------- 49 50 #include "G4LowEnergyGammaConversion.hh" 51 52 #include "Randomize.hh" 53 #include "G4PhysicalConstants.hh" 54 #include "G4SystemOfUnits.hh" 55 #include "G4ParticleDefinition.hh" 56 #include "G4Track.hh" 57 #include "G4Step.hh" 58 #include "G4ForceCondition.hh" 59 #include "G4Gamma.hh" 60 #include "G4Electron.hh" 61 #include "G4DynamicParticle.hh" 62 #include "G4VParticleChange.hh" 63 #include "G4ThreeVector.hh" 64 #include "G4Positron.hh" 65 #include "G4IonisParamElm.hh" 66 #include "G4Material.hh" 67 #include "G4RDVCrossSectionHandler.hh" 68 #include "G4RDCrossSectionHandler.hh" 69 #include "G4RDVEMDataSet.hh" 70 #include "G4RDVDataSetAlgorithm.hh" 71 #include "G4RDLogLogInterpolation.hh" 72 #include "G4RDVRangeTest.hh" 73 #include "G4RDRangeTest.hh" 74 #include "G4MaterialCutsCouple.hh" 75 76 G4LowEnergyGammaConversion::G4LowEnergyGammaCo 77 : G4VDiscreteProcess(processName), 78 lowEnergyLimit(1.022000*MeV), 79 highEnergyLimit(100*GeV), 80 intrinsicLowEnergyLimit(1.022000*MeV), 81 intrinsicHighEnergyLimit(100*GeV), 82 smallEnergy(2.*MeV) 83 84 { 85 if (lowEnergyLimit < intrinsicLowEnergyLimit 86 highEnergyLimit > intrinsicHighEnergyLim 87 { 88 G4Exception("G4LowEnergyGammaConversion: 89 "OutOfRange", FatalException 90 "Energy limit outside intrin 91 } 92 93 // The following pointer is owned by G4DataH 94 95 crossSectionHandler = new G4RDCrossSectionHa 96 crossSectionHandler->Initialise(0,1.0220*MeV 97 meanFreePathTable = 0; 98 rangeTest = new G4RDRangeTest; 99 100 if (verboseLevel > 0) 101 { 102 G4cout << GetProcessName() << " is crea 103 << "Energy range: " 104 << lowEnergyLimit / MeV << " MeV - " 105 << highEnergyLimit / GeV << " GeV" 106 << G4endl; 107 } 108 } 109 110 G4LowEnergyGammaConversion::~G4LowEnergyGammaC 111 { 112 delete meanFreePathTable; 113 delete crossSectionHandler; 114 delete rangeTest; 115 } 116 117 void G4LowEnergyGammaConversion::BuildPhysicsT 118 { 119 120 crossSectionHandler->Clear(); 121 G4String crossSectionFile = "pair/pp-cs-"; 122 crossSectionHandler->LoadData(crossSectionFi 123 124 delete meanFreePathTable; 125 meanFreePathTable = crossSectionHandler->Bui 126 } 127 128 G4VParticleChange* G4LowEnergyGammaConversion: 129 const G4Step& aStep) 130 { 131 // The energies of the e+ e- secondaries are s 132 // cross sections with Coulomb correction. A m 133 // number techniques of Butcher & Messel is us 134 135 // Note 1 : Effects due to the breakdown of th 136 // energy are ignored. 137 // Note 2 : The differential cross section imp 138 // pair creation in both nuclear and atomic el 139 // prodution is not generated. 140 141 aParticleChange.Initialize(aTrack); 142 143 const G4MaterialCutsCouple* couple = aTrack. 144 145 const G4DynamicParticle* incidentPhoton = aT 146 G4double photonEnergy = incidentPhoton->GetK 147 G4ParticleMomentum photonDirection = inciden 148 149 G4double epsilon ; 150 G4double epsilon0 = electron_mass_c2 / photo 151 152 // Do it fast if photon energy < 2. MeV 153 if (photonEnergy < smallEnergy ) 154 { 155 epsilon = epsilon0 + (0.5 - epsilon0) * 156 } 157 else 158 { 159 // Select randomly one element in the cu 160 const G4Element* element = crossSectionH 161 162 if (element == 0) 163 { 164 G4cout << "G4LowEnergyGammaConversion::Pos 165 } 166 G4IonisParamElm* ionisation = element->G 167 if (ionisation == 0) 168 { 169 G4cout << "G4LowEnergyGammaConversion::Pos 170 } 171 172 // Extract Coulomb factor for this Eleme 173 G4double fZ = 8. * (ionisation->GetlogZ3 174 if (photonEnergy > 50. * MeV) fZ += 8. * 175 176 // Limits of the screening variable 177 G4double screenFactor = 136. * epsilon0 178 G4double screenMax = std::exp ((42.24 - 179 G4double screenMin = std::min(4.*screenF 180 181 // Limits of the energy sampling 182 G4double epsilon1 = 0.5 - 0.5 * std::sqr 183 G4double epsilonMin = std::max(epsilon0, 184 G4double epsilonRange = 0.5 - epsilonMin 185 186 // Sample the energy rate of the created 187 G4double screen; 188 G4double gReject ; 189 190 G4double f10 = ScreenFunction1(screenMin 191 G4double f20 = ScreenFunction2(screenMin 192 G4double normF1 = std::max(f10 * epsilon 193 G4double normF2 = std::max(1.5 * f20,0.) 194 195 do { 196 if (normF1 / (normF1 + normF2) > G4UniformRa 197 { 198 epsilon = 0.5 - epsilonRange * std::pow( 199 screen = screenFactor / (epsilon * (1. - 200 gReject = (ScreenFunction1(screen) - fZ) 201 } 202 else 203 { 204 epsilon = epsilonMin + epsilonRange * G4 205 screen = screenFactor / (epsilon * (1 - 206 gReject = (ScreenFunction2(screen) - fZ) 207 } 208 } while ( gReject < G4UniformRand() ); 209 210 } // End of epsilon sampling 211 212 // Fix charges randomly 213 214 G4double electronTotEnergy; 215 G4double positronTotEnergy; 216 217 if (CLHEP::RandBit::shootBit()) 218 { 219 electronTotEnergy = (1. - epsilon) * pho 220 positronTotEnergy = epsilon * photonEner 221 } 222 else 223 { 224 positronTotEnergy = (1. - epsilon) * pho 225 electronTotEnergy = epsilon * photonEner 226 } 227 228 // Scattered electron (positron) angles. ( Z 229 // Universal distribution suggested by L. Ur 230 // derived from Tsai distribution (Rev. Mod. 231 232 G4double u; 233 const G4double a1 = 0.625; 234 G4double a2 = 3. * a1; 235 // G4double d = 27. ; 236 237 // if (9. / (9. + d) > G4UniformRand()) 238 if (0.25 > G4UniformRand()) 239 { 240 u = - std::log(G4UniformRand() * G4Unifo 241 } 242 else 243 { 244 u = - std::log(G4UniformRand() * G4Unifo 245 } 246 247 G4double thetaEle = u*electron_mass_c2/elect 248 G4double thetaPos = u*electron_mass_c2/posit 249 G4double phi = twopi * G4UniformRand(); 250 251 G4double dxEle= std::sin(thetaEle)*std::cos( 252 G4double dxPos=-std::sin(thetaPos)*std::cos( 253 254 255 // Kinematics of the created pair: 256 // the electron and positron are assumed to 257 // distribution with respect to the Z axis a 258 259 G4double localEnergyDeposit = 0. ; 260 261 aParticleChange.SetNumberOfSecondaries(2) ; 262 G4double electronKineEnergy = std::max(0.,el 263 264 // Generate the electron only if with large 265 266 G4double safety = aStep.GetPostStepPoint()-> 267 268 if (rangeTest->Escape(G4Electron::Electron() 269 { 270 G4ThreeVector electronDirection (dxEle, 271 electronDirection.rotateUz(photonDirecti 272 273 G4DynamicParticle* particle1 = new G4Dyn 274 electronDirection, 275 electronKineEnergy); 276 aParticleChange.AddSecondary(particle1) 277 } 278 else 279 { 280 localEnergyDeposit += electronKineEnergy 281 } 282 283 // The e+ is always created (even with kinet 284 G4double positronKineEnergy = std::max(0.,po 285 286 // Is the local energy deposit correct, if t 287 if (! (rangeTest->Escape(G4Positron::Positro 288 { 289 localEnergyDeposit += positronKineEnergy 290 positronKineEnergy = 0. ; 291 } 292 293 G4ThreeVector positronDirection (dxPos, dyPo 294 positronDirection.rotateUz(photonDirection); 295 296 // Create G4DynamicParticle object for the p 297 G4DynamicParticle* particle2 = new G4Dynamic 298 positronDirection, positron 299 aParticleChange.AddSecondary(particle2) ; 300 301 aParticleChange.ProposeLocalEnergyDeposit(lo 302 303 // Kill the incident photon 304 aParticleChange.ProposeMomentumDirection(0., 305 aParticleChange.ProposeEnergy(0.) ; 306 aParticleChange.ProposeTrackStatus(fStopAndK 307 308 // Reset NbOfInteractionLengthLeft and retu 309 return G4VDiscreteProcess::PostStepDoIt(aTra 310 } 311 312 G4bool G4LowEnergyGammaConversion::IsApplicabl 313 { 314 return ( &particle == G4Gamma::Gamma() ); 315 } 316 317 G4double G4LowEnergyGammaConversion::GetMeanFr 318 G4double, // previousStepSize 319 G4ForceCondition*) 320 { 321 const G4DynamicParticle* photon = track.GetD 322 G4double energy = photon->GetKineticEnergy() 323 const G4MaterialCutsCouple* couple = track.G 324 size_t materialIndex = couple->GetIndex(); 325 326 G4double meanFreePath; 327 if (energy > highEnergyLimit) meanFreePath = 328 else if (energy < lowEnergyLimit) meanFreePa 329 else meanFreePath = meanFreePathTable->FindV 330 return meanFreePath; 331 } 332 333 G4double G4LowEnergyGammaConversion::ScreenFun 334 { 335 // Compute the value of the screening functi 336 337 G4double value; 338 339 if (screenVariable > 1.) 340 value = 42.24 - 8.368 * std::log(screenVar 341 else 342 value = 42.392 - screenVariable * (7.796 - 343 344 return value; 345 } 346 347 G4double G4LowEnergyGammaConversion::ScreenFun 348 { 349 // Compute the value of the screening functi 350 351 G4double value; 352 353 if (screenVariable > 1.) 354 value = 42.24 - 8.368 * std::log(screenVar 355 else 356 value = 41.405 - screenVariable * (5.828 - 357 358 return value; 359 } 360