Geant4: G4LivermoreGammaConversionModel Class Reference

G4LivermoreGammaConversionModel::G4LivermoreGammaConversionModel	(	const G4ParticleDefinition *	p = `0`,
		const G4String &	nam = `"LivermoreConversion"`
	)

Definition at line 40 of file G4LivermoreGammaConversionModel.cc.

References G4cout, and G4endl.

00042 :G4VEmModel(nam),smallEnergy(2.*MeV),isInitialised(false),maxZ(99)
00043 {
00044   fParticleChange = 0;
00045 
00046   lowEnergyLimit = 2.0*electron_mass_c2;
00047   data.resize(maxZ+1,0); 
00048          
00049   verboseLevel= 0;
00050   // Verbosity scale for debugging purposes:
00051   // 0 = nothing 
00052   // 1 = calculation of cross sections, file openings...
00053   // 2 = entering in methods
00054 
00055   if(verboseLevel > 0) 
00056   {
00057     G4cout << "G4LivermoreGammaConversionModel is constructed " << G4endl;
00058   }
00059 }

G4LivermoreGammaConversionModel::~G4LivermoreGammaConversionModel ( ) [virtual]

Definition at line 63 of file G4LivermoreGammaConversionModel.cc.

00064 {  
00065   for(G4int i=0; i<=maxZ; ++i) { delete data[i]; }
00066 }

G4double G4LivermoreGammaConversionModel::ComputeCrossSectionPerAtom	(	const G4ParticleDefinition *	,
		G4double	kinEnergy,
		G4double	Z,
		G4double	A = `0`,
		G4double	cut = `0`,
		G4double	emax = `DBL_MAX`
	)			`[virtual]`

Reimplemented from G4VEmModel.

Definition at line 182 of file G4LivermoreGammaConversionModel.cc.

References G4cout, G4endl, G4PhysicsVector::GetVectorLength(), CLHEP::detail::n, and G4PhysicsVector::Value().

00186 {
00187   if (verboseLevel > 1) 
00188   {
00189     G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreGammaConversionModel" 
00190            << G4endl;
00191   }
00192 
00193   if (GammaEnergy < lowEnergyLimit) { return 0.0; } 
00194 
00195   G4double xs = 0.0;
00196   
00197   G4int intZ=G4int(Z);
00198 
00199   if(intZ < 1 || intZ > maxZ) { return xs; }
00200 
00201   G4LPhysicsFreeVector* pv = data[intZ];
00202 
00203   // element was not initialised
00204   if(!pv) 
00205   {
00206     char* path = getenv("G4LEDATA");
00207     ReadData(intZ, path);
00208     pv = data[intZ];
00209     if(!pv) { return xs; }
00210   }
00211   // x-section is taken from the table
00212   xs = pv->Value(GammaEnergy); 
00213 
00214   if(verboseLevel > 0)
00215   {
00216     G4int n = pv->GetVectorLength() - 1;
00217     G4cout  <<  "****** DEBUG: tcs value for Z=" << Z << " at energy (MeV)=" << GammaEnergy/MeV << G4endl;
00218     G4cout  <<  "  cs (Geant4 internal unit)=" << xs << G4endl;
00219     G4cout  <<  "    -> first cs value in EADL data file (iu) =" << (*pv)[0] << G4endl;
00220     G4cout  <<  "    -> last  cs value in EADL data file (iu) =" << (*pv)[n] << G4endl;
00221     G4cout  <<  "*********************************************************" << G4endl;
00222   }
00223 
00224   return xs;
00225 
00226 }

void G4LivermoreGammaConversionModel::Initialise	(	const G4ParticleDefinition *	,
		const G4DataVector &
	)			`[virtual]`

Implements G4VEmModel.

Definition at line 71 of file G4LivermoreGammaConversionModel.cc.

References G4cout, G4endl, G4MaterialCutsCouple::GetMaterial(), G4ProductionCutsTable::GetMaterialCutsCouple(), G4VEmModel::GetParticleChangeForGamma(), G4ProductionCutsTable::GetProductionCutsTable(), G4ProductionCutsTable::GetTableSize(), G4VEmModel::HighEnergyLimit(), G4VEmModel::InitialiseElementSelectors(), and G4VEmModel::LowEnergyLimit().

00073 {
00074   if (verboseLevel > 1) 
00075   {
00076     G4cout << "Calling Initialise() of G4LivermoreGammaConversionModel." << G4endl
00077            << "Energy range: "
00078            << LowEnergyLimit() / MeV << " MeV - "
00079            << HighEnergyLimit() / GeV << " GeV"
00080            << G4endl;
00081   }
00082 
00083   // Initialise element selector
00084   
00085   InitialiseElementSelectors(particle, cuts);
00086 
00087   // Access to elements
00088   
00089   char* path = getenv("G4LEDATA");
00090 
00091   G4ProductionCutsTable* theCoupleTable =
00092     G4ProductionCutsTable::GetProductionCutsTable();
00093   G4int numOfCouples = theCoupleTable->GetTableSize();
00094   
00095   for(G4int i=0; i<numOfCouples; ++i) 
00096   {
00097     const G4Material* material = 
00098       theCoupleTable->GetMaterialCutsCouple(i)->GetMaterial();
00099     const G4ElementVector* theElementVector = material->GetElementVector();
00100     G4int nelm = material->GetNumberOfElements();
00101     
00102     for (G4int j=0; j<nelm; ++j) 
00103     {
00104         
00105       G4int Z = (G4int)(*theElementVector)[j]->GetZ();
00106       if(Z < 1)          { Z = 1; }
00107       else if(Z > maxZ)  { Z = maxZ; }
00108       if(!data[Z]) { ReadData(Z, path); }
00109     }
00110   }
00111   //
00112   
00113   if(isInitialised) { return; }
00114   fParticleChange = GetParticleChangeForGamma();
00115   isInitialised = true;
00116 }

void G4LivermoreGammaConversionModel::SampleSecondaries	(	std::vector< G4DynamicParticle * > *	,
		const G4MaterialCutsCouple *	,
		const G4DynamicParticle *	,
		G4double	tmin,
		G4double	maxEnergy
	)			`[virtual]`

Implements G4VEmModel.

Definition at line 230 of file G4LivermoreGammaConversionModel.cc.

References G4Electron::Electron(), fStopAndKill, G4cout, G4endl, G4UniformRand, G4DynamicParticle::GetDefinition(), G4Element::GetfCoulomb(), G4Element::GetIonisation(), G4DynamicParticle::GetKineticEnergy(), G4IonisParamElm::GetlogZ3(), G4DynamicParticle::GetMomentumDirection(), G4IonisParamElm::GetZ3(), G4Positron::Positron(), G4VParticleChange::ProposeTrackStatus(), G4VEmModel::SelectRandomAtom(), and G4ParticleChangeForGamma::SetProposedKineticEnergy().

00235 {
00236 
00237 // The energies of the e+ e- secondaries are sampled using the Bethe - Heitler
00238 // cross sections with Coulomb correction. A modified version of the random
00239 // number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15).
00240 
00241 // Note 1 : Effects due to the breakdown of the Born approximation at low
00242 // energy are ignored.
00243 // Note 2 : The differential cross section implicitly takes account of
00244 // pair creation in both nuclear and atomic electron fields. However triplet
00245 // prodution is not generated.
00246 
00247   if (verboseLevel > 1)
00248     G4cout << "Calling SampleSecondaries() of G4LivermoreGammaConversionModel" << G4endl;
00249 
00250   G4double photonEnergy = aDynamicGamma->GetKineticEnergy();
00251   G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection();
00252 
00253   G4double epsilon ;
00254   G4double epsilon0Local = electron_mass_c2 / photonEnergy ;
00255 
00256   // Do it fast if photon energy < 2. MeV
00257   if (photonEnergy < smallEnergy )
00258   {
00259     epsilon = epsilon0Local + (0.5 - epsilon0Local) * G4UniformRand();
00260   }
00261   else
00262   {
00263     // Select randomly one element in the current material
00264 
00265     const G4ParticleDefinition* particle =  aDynamicGamma->GetDefinition();
00266     const G4Element* element = SelectRandomAtom(couple,particle,photonEnergy);
00267 
00268     if (element == 0)
00269       {
00270         G4cout << "G4LivermoreGammaConversionModel::SampleSecondaries - element = 0" 
00271                << G4endl;
00272         return;
00273       }
00274     G4IonisParamElm* ionisation = element->GetIonisation();
00275     if (ionisation == 0)
00276       {
00277         G4cout << "G4LivermoreGammaConversionModel::SampleSecondaries - ionisation = 0" 
00278                << G4endl;
00279         return;
00280       }
00281 
00282     // Extract Coulomb factor for this Element
00283     G4double fZ = 8. * (ionisation->GetlogZ3());
00284     if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb());
00285 
00286     // Limits of the screening variable
00287     G4double screenFactor = 136. * epsilon0Local / (element->GetIonisation()->GetZ3()) ;
00288     G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ;
00289     G4double screenMin = std::min(4.*screenFactor,screenMax) ;
00290 
00291     // Limits of the energy sampling
00292     G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ;
00293     G4double epsilonMin = std::max(epsilon0Local,epsilon1);
00294     G4double epsilonRange = 0.5 - epsilonMin ;
00295 
00296     // Sample the energy rate of the created electron (or positron)
00297     G4double screen;
00298     G4double gReject ;
00299 
00300     G4double f10 = ScreenFunction1(screenMin) - fZ;
00301     G4double f20 = ScreenFunction2(screenMin) - fZ;
00302     G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.);
00303     G4double normF2 = std::max(1.5 * f20,0.);
00304 
00305     do 
00306       {
00307         if (normF1 / (normF1 + normF2) > G4UniformRand() )
00308           {
00309             epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.333333) ;
00310             screen = screenFactor / (epsilon * (1. - epsilon));
00311             gReject = (ScreenFunction1(screen) - fZ) / f10 ;
00312           }
00313         else
00314           {
00315             epsilon = epsilonMin + epsilonRange * G4UniformRand();
00316             screen = screenFactor / (epsilon * (1 - epsilon));
00317             gReject = (ScreenFunction2(screen) - fZ) / f20 ;
00318           }
00319       } while ( gReject < G4UniformRand() );
00320     
00321   }   //  End of epsilon sampling
00322 
00323   // Fix charges randomly
00324 
00325   G4double electronTotEnergy;
00326   G4double positronTotEnergy;
00327 
00328   if (G4UniformRand() > 0.5)
00329     {
00330       electronTotEnergy = (1. - epsilon) * photonEnergy;
00331       positronTotEnergy = epsilon * photonEnergy;
00332     }
00333   else
00334     {
00335       positronTotEnergy = (1. - epsilon) * photonEnergy;
00336       electronTotEnergy = epsilon * photonEnergy;
00337     }
00338 
00339   // Scattered electron (positron) angles. ( Z - axis along the parent photon)
00340   // Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211),
00341   // derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977)
00342 
00343   G4double u;
00344   const G4double a1 = 0.625;
00345   G4double a2 = 3. * a1;
00346   //  G4double d = 27. ;
00347 
00348   //  if (9. / (9. + d) > G4UniformRand())
00349   if (0.25 > G4UniformRand())
00350     {
00351       u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ;
00352     }
00353   else
00354     {
00355       u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ;
00356     }
00357 
00358   G4double thetaEle = u*electron_mass_c2/electronTotEnergy;
00359   G4double thetaPos = u*electron_mass_c2/positronTotEnergy;
00360   G4double phi  = twopi * G4UniformRand();
00361 
00362   G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle);
00363   G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos);
00364   
00365   
00366   // Kinematics of the created pair:
00367   // the electron and positron are assumed to have a symetric angular 
00368   // distribution with respect to the Z axis along the parent photon
00369   
00370   G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ;
00371   
00372   G4ThreeVector electronDirection (dxEle, dyEle, dzEle);
00373   electronDirection.rotateUz(photonDirection);
00374       
00375   G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(),
00376                                                         electronDirection,
00377                                                         electronKineEnergy);
00378 
00379   // The e+ is always created 
00380   G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
00381 
00382   G4ThreeVector positronDirection (dxPos, dyPos, dzPos);
00383   positronDirection.rotateUz(photonDirection);   
00384   
00385   // Create G4DynamicParticle object for the particle2 
00386   G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(),
00387                                                        positronDirection, 
00388                                                        positronKineEnergy);
00389   // Fill output vector
00390   fvect->push_back(particle1);
00391   fvect->push_back(particle2);
00392 
00393   // kill incident photon
00394   fParticleChange->SetProposedKineticEnergy(0.);
00395   fParticleChange->ProposeTrackStatus(fStopAndKill);   
00396 
00397 }


Public Member Functions
	G4LivermoreGammaConversionModel (const G4ParticleDefinition *p=0, const G4String &nam="LivermoreConversion")
virtual	~G4LivermoreGammaConversionModel ()
virtual void	Initialise (const G4ParticleDefinition *, const G4DataVector &)
virtual G4double	ComputeCrossSectionPerAtom (const G4ParticleDefinition *, G4double kinEnergy, G4double Z, G4double A=0, G4double cut=0, G4double emax=DBL_MAX)
virtual void	SampleSecondaries (std::vector< G4DynamicParticle * > , const G4MaterialCutsCouple , const G4DynamicParticle *, G4double tmin, G4double maxEnergy)

G4LivermoreGammaConversionModel Class Reference

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation