Geant4: G4LivermoreNuclearGammaConversionModel Class Reference

G4LivermoreNuclearGammaConversionModel::G4LivermoreNuclearGammaConversionModel	(	const G4ParticleDefinition *	p = `0`,
		const G4String &	nam = `"LivermoreNuclearGammaConversion"`
	)

Definition at line 41 of file G4LivermoreNuclearGammaConversionModel.cc.

References G4cout, G4endl, and G4VEmModel::SetHighEnergyLimit().

00043   :G4VEmModel(nam),fParticleChange(0),smallEnergy(2.*MeV),
00044    isInitialised(false),
00045    crossSectionHandler(0),meanFreePathTable(0)
00046 {
00047   lowEnergyLimit = 2.0*electron_mass_c2;
00048   highEnergyLimit = 100 * GeV;
00049   SetHighEnergyLimit(highEnergyLimit);
00050          
00051   verboseLevel= 0;
00052   // Verbosity scale:
00053   // 0 = nothing 
00054   // 1 = warning for energy non-conservation 
00055   // 2 = details of energy budget
00056   // 3 = calculation of cross sections, file openings, sampling of atoms
00057   // 4 = entering in methods
00058 
00059   if(verboseLevel > 0) {
00060     G4cout << "Livermore Nuclear Gamma conversion is constructed " << G4endl
00061            << "Energy range: "
00062            << lowEnergyLimit / MeV << " MeV - "
00063            << highEnergyLimit / GeV << " GeV"
00064            << G4endl;
00065   }
00066 }

G4LivermoreNuclearGammaConversionModel::~G4LivermoreNuclearGammaConversionModel ( ) [virtual]

Definition at line 70 of file G4LivermoreNuclearGammaConversionModel.cc.

00071 {  
00072   if (crossSectionHandler) delete crossSectionHandler;
00073 }

G4double G4LivermoreNuclearGammaConversionModel::ComputeCrossSectionPerAtom	(	const G4ParticleDefinition *	,
		G4double	kinEnergy,
		G4double	Z,
		G4double	A = `0`,
		G4double	cut = `0`,
		G4double	emax = `DBL_MAX`
	)			`[virtual]`

Reimplemented from G4VEmModel.

Definition at line 121 of file G4LivermoreNuclearGammaConversionModel.cc.

References G4VCrossSectionHandler::FindValue(), G4cout, and G4endl.

00125 {
00126   if (verboseLevel > 3) {
00127     G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreNuclearGammaConversionModel" 
00128            << G4endl;
00129   }
00130   if (GammaEnergy < lowEnergyLimit || GammaEnergy > highEnergyLimit) return 0;
00131 
00132   G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
00133   return cs;
00134 }

G4double G4LivermoreNuclearGammaConversionModel::GetMeanFreePath	(	const G4Track &	aTrack,
		G4double	previousStepSize,
		G4ForceCondition *	condition
	)			`[protected]`

void G4LivermoreNuclearGammaConversionModel::Initialise	(	const G4ParticleDefinition *	,
		const G4DataVector &
	)			`[virtual]`

Implements G4VEmModel.

Definition at line 78 of file G4LivermoreNuclearGammaConversionModel.cc.

References G4VCrossSectionHandler::Clear(), fParticleChange, G4cout, G4endl, G4VEmModel::GetParticleChangeForGamma(), G4VEmModel::HighEnergyLimit(), G4VCrossSectionHandler::Initialise(), G4VCrossSectionHandler::LoadData(), and G4VEmModel::LowEnergyLimit().

00080 {
00081   if (verboseLevel > 3)
00082     G4cout << "Calling G4LivermoreNuclearGammaConversionModel::Initialise()" << G4endl;
00083 
00084   if (crossSectionHandler)
00085   {
00086     crossSectionHandler->Clear();
00087     delete crossSectionHandler;
00088   }
00089 
00090   // Read data tables for all materials
00091   
00092   crossSectionHandler = new G4CrossSectionHandler();
00093   crossSectionHandler->Initialise(0,lowEnergyLimit,100.*GeV,400);
00094   G4String crossSectionFile = "pairdata/pp-pair-cs-"; // here only pair in nuclear field cs should be used
00095   crossSectionHandler->LoadData(crossSectionFile);
00096 
00097   //
00098   
00099   if (verboseLevel > 0) {
00100     G4cout << "Loaded cross section files for Livermore GammaConversion" << G4endl;
00101     G4cout << "To obtain the total cross section this should be used only " << G4endl 
00102            << "in connection with G4ElectronGammaConversion " << G4endl;
00103   }
00104 
00105   if (verboseLevel > 0) { 
00106     G4cout << "Livermore Nuclear Gamma Conversion model is initialized " << G4endl
00107            << "Energy range: "
00108            << LowEnergyLimit() / MeV << " MeV - "
00109            << HighEnergyLimit() / GeV << " GeV"
00110            << G4endl;
00111   }
00112 
00113   if(isInitialised) return;
00114   fParticleChange = GetParticleChangeForGamma();
00115   isInitialised = true;
00116 }

void G4LivermoreNuclearGammaConversionModel::SampleSecondaries	(	std::vector< G4DynamicParticle * > *	,
		const G4MaterialCutsCouple *	,
		const G4DynamicParticle *	,
		G4double	tmin,
		G4double	maxEnergy
	)			`[virtual]`

Implements G4VEmModel.

Definition at line 138 of file G4LivermoreNuclearGammaConversionModel.cc.

References G4Electron::Electron(), fParticleChange, 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().

00143 {
00144 
00145 // The energies of the e+ e- secondaries are sampled using the Bethe - Heitler
00146 // cross sections with Coulomb correction. A modified version of the random
00147 // number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15).
00148 
00149 // Note 1 : Effects due to the breakdown of the Born approximation at low
00150 // energy are ignored.
00151 // Note 2 : The differential cross section implicitly takes account of
00152 // pair creation in both nuclear and atomic electron fields. However triplet
00153 // prodution is not generated.
00154 
00155   if (verboseLevel > 3)
00156     G4cout << "Calling SampleSecondaries() of G4LivermoreNuclearGammaConversionModel" << G4endl;
00157 
00158   G4double photonEnergy = aDynamicGamma->GetKineticEnergy();
00159   G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection();
00160 
00161   G4double epsilon ;
00162   G4double epsilon0Local = electron_mass_c2 / photonEnergy ;
00163 
00164   // Do it fast if photon energy < 2. MeV
00165   if (photonEnergy < smallEnergy )
00166     {
00167       epsilon = epsilon0Local + (0.5 - epsilon0Local) * G4UniformRand();
00168     }
00169   else
00170     {
00171       // Select randomly one element in the current material
00172       //const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy);
00173       const G4ParticleDefinition* particle =  aDynamicGamma->GetDefinition();
00174       const G4Element* element = SelectRandomAtom(couple,particle,photonEnergy);
00175 
00176       if (element == 0)
00177         {
00178           G4cout << "G4LivermoreNuclearGammaConversionModel::SampleSecondaries - element = 0" 
00179                  << G4endl;
00180           return;
00181         }
00182       G4IonisParamElm* ionisation = element->GetIonisation();
00183       if (ionisation == 0)
00184         {
00185           G4cout << "G4LivermoreNuclearGammaConversionModel::SampleSecondaries - ionisation = 0" 
00186                  << G4endl;
00187           return;
00188         }
00189 
00190       // Extract Coulomb factor for this Element
00191       G4double fZ = 8. * (ionisation->GetlogZ3());
00192       if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb());
00193 
00194       // Limits of the screening variable
00195       G4double screenFactor = 136. * epsilon0Local / (element->GetIonisation()->GetZ3()) ;
00196       G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ;
00197       G4double screenMin = std::min(4.*screenFactor,screenMax) ;
00198 
00199       // Limits of the energy sampling
00200       G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ;
00201       G4double epsilonMin = std::max(epsilon0Local,epsilon1);
00202       G4double epsilonRange = 0.5 - epsilonMin ;
00203 
00204       // Sample the energy rate of the created electron (or positron)
00205       G4double screen;
00206       G4double gReject ;
00207 
00208       G4double f10 = ScreenFunction1(screenMin) - fZ;
00209       G4double f20 = ScreenFunction2(screenMin) - fZ;
00210       G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.);
00211       G4double normF2 = std::max(1.5 * f20,0.);
00212 
00213       do {
00214         if (normF1 / (normF1 + normF2) > G4UniformRand() )
00215           {
00216             epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.3333) ;
00217             screen = screenFactor / (epsilon * (1. - epsilon));
00218             gReject = (ScreenFunction1(screen) - fZ) / f10 ;
00219           }
00220         else
00221           {
00222             epsilon = epsilonMin + epsilonRange * G4UniformRand();
00223             screen = screenFactor / (epsilon * (1 - epsilon));
00224             gReject = (ScreenFunction2(screen) - fZ) / f20 ;
00225           }
00226       } while ( gReject < G4UniformRand() );
00227 
00228     }   //  End of epsilon sampling
00229 
00230   // Fix charges randomly
00231 
00232   G4double electronTotEnergy;
00233   G4double positronTotEnergy;
00234 
00235   if (G4int(2*G4UniformRand()))    
00236     {
00237       electronTotEnergy = (1. - epsilon) * photonEnergy;
00238       positronTotEnergy = epsilon * photonEnergy;
00239     }
00240   else
00241     {
00242       positronTotEnergy = (1. - epsilon) * photonEnergy;
00243       electronTotEnergy = epsilon * photonEnergy;
00244     }
00245 
00246   // Scattered electron (positron) angles. ( Z - axis along the parent photon)
00247   // Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211),
00248   // derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977)
00249 
00250   G4double u;
00251   const G4double a1 = 0.625;
00252   G4double a2 = 3. * a1;
00253   //  G4double d = 27. ;
00254 
00255   //  if (9. / (9. + d) > G4UniformRand())
00256   if (0.25 > G4UniformRand())
00257     {
00258       u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ;
00259     }
00260   else
00261     {
00262       u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ;
00263     }
00264 
00265   G4double thetaEle = u*electron_mass_c2/electronTotEnergy;
00266   G4double thetaPos = u*electron_mass_c2/positronTotEnergy;
00267   G4double phi  = twopi * G4UniformRand();
00268 
00269   G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle);
00270   G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos);
00271   
00272   
00273   // Kinematics of the created pair:
00274   // the electron and positron are assumed to have a symetric angular 
00275   // distribution with respect to the Z axis along the parent photon
00276   
00277   G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ;
00278   
00279   // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
00280 
00281   G4ThreeVector electronDirection (dxEle, dyEle, dzEle);
00282   electronDirection.rotateUz(photonDirection);
00283       
00284   G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(),
00285                                                             electronDirection,
00286                                                             electronKineEnergy);
00287 
00288   // The e+ is always created (even with kinetic energy = 0) for further annihilation
00289   G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
00290 
00291   // SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
00292 
00293   G4ThreeVector positronDirection (dxPos, dyPos, dzPos);
00294   positronDirection.rotateUz(photonDirection);   
00295   
00296   // Create G4DynamicParticle object for the particle2 
00297   G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(),
00298                                                        positronDirection, positronKineEnergy);
00299   // Fill output vector
00300 
00301   fvect->push_back(particle1);
00302   fvect->push_back(particle2);
00303 
00304   // kill incident photon
00305   fParticleChange->SetProposedKineticEnergy(0.);
00306   fParticleChange->ProposeTrackStatus(fStopAndKill);   
00307 
00308 }

G4ParticleChangeForGamma* G4LivermoreNuclearGammaConversionModel::fParticleChange [protected]

Definition at line 71 of file G4LivermoreNuclearGammaConversionModel.hh.

Referenced by Initialise(), and SampleSecondaries().


Public Member Functions
	G4LivermoreNuclearGammaConversionModel (const G4ParticleDefinition *p=0, const G4String &nam="LivermoreNuclearGammaConversion")
virtual	~G4LivermoreNuclearGammaConversionModel ()
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)
Protected Member Functions
G4double	GetMeanFreePath (const G4Track &aTrack, G4double previousStepSize, G4ForceCondition *condition)
Protected Attributes
G4ParticleChangeForGamma *	fParticleChange

G4LivermoreNuclearGammaConversionModel Class Reference

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Field Documentation