G4LowEnergyGammaConversion Class Reference

#include <G4LowEnergyGammaConversion.hh>

Inheritance diagram for G4LowEnergyGammaConversion:

Collaboration diagram for G4LowEnergyGammaConversion:

Public Member Functions
	G4LowEnergyGammaConversion (const G4String &processName="LowEnConversion")
	~G4LowEnergyGammaConversion ()
G4bool	IsApplicable (const G4ParticleDefinition &photon)
void	BuildPhysicsTable (const G4ParticleDefinition &photon)
G4VParticleChange *	PostStepDoIt (const G4Track &aTrack, const G4Step &aStep)
G4double	DumpMeanFreePath (const G4Track &aTrack, G4double previousStepSize, G4ForceCondition *condition)
Public Member Functions inherited from G4VDiscreteProcess
	G4VDiscreteProcess (const G4String &, G4ProcessType aType=fNotDefined)
	G4VDiscreteProcess (G4VDiscreteProcess &)
virtual	~G4VDiscreteProcess ()
virtual G4double	PostStepGetPhysicalInteractionLength (const G4Track &track, G4double previousStepSize, G4ForceCondition *condition)
virtual G4double	AlongStepGetPhysicalInteractionLength (const G4Track &, G4double, G4double, G4double &, G4GPILSelection *)
virtual G4double	AtRestGetPhysicalInteractionLength (const G4Track &, G4ForceCondition *)
virtual G4VParticleChange *	AtRestDoIt (const G4Track &, const G4Step &)
virtual G4VParticleChange *	AlongStepDoIt (const G4Track &, const G4Step &)
Public Member Functions inherited from G4VProcess
	G4VProcess (const G4String &aName="NoName", G4ProcessType aType=fNotDefined)
	G4VProcess (const G4VProcess &right)
virtual	~G4VProcess ()
G4int	operator== (const G4VProcess &right) const
G4int	operator!= (const G4VProcess &right) const
G4double	GetCurrentInteractionLength () const
void	SetPILfactor (G4double value)
G4double	GetPILfactor () const
G4double	AlongStepGPIL (const G4Track &track, G4double previousStepSize, G4double currentMinimumStep, G4double &proposedSafety, G4GPILSelection *selection)
G4double	AtRestGPIL (const G4Track &track, G4ForceCondition *condition)
G4double	PostStepGPIL (const G4Track &track, G4double previousStepSize, G4ForceCondition *condition)
virtual void	PreparePhysicsTable (const G4ParticleDefinition &)
virtual G4bool	StorePhysicsTable (const G4ParticleDefinition *, const G4String &, G4bool)
virtual G4bool	RetrievePhysicsTable (const G4ParticleDefinition *, const G4String &, G4bool)
const G4String &	GetPhysicsTableFileName (const G4ParticleDefinition *, const G4String &directory, const G4String &tableName, G4bool ascii=false)
const G4String &	GetProcessName () const
G4ProcessType	GetProcessType () const
void	SetProcessType (G4ProcessType)
G4int	GetProcessSubType () const
void	SetProcessSubType (G4int)
virtual void	StartTracking (G4Track *)
virtual void	EndTracking ()
virtual void	SetProcessManager (const G4ProcessManager *)
virtual const G4ProcessManager *	GetProcessManager ()
virtual void	ResetNumberOfInteractionLengthLeft ()
G4double	GetNumberOfInteractionLengthLeft () const
G4double	GetTotalNumberOfInteractionLengthTraversed () const
G4bool	isAtRestDoItIsEnabled () const
G4bool	isAlongStepDoItIsEnabled () const
G4bool	isPostStepDoItIsEnabled () const
virtual void	DumpInfo () const
void	SetVerboseLevel (G4int value)
G4int	GetVerboseLevel () const
virtual void	SetMasterProcess (G4VProcess *masterP)
const G4VProcess *	GetMasterProcess () const
virtual void	BuildWorkerPhysicsTable (const G4ParticleDefinition &part)
virtual void	PrepareWorkerPhysicsTable (const G4ParticleDefinition &)

Protected Member Functions
G4double	GetMeanFreePath (const G4Track &aTrack, G4double previousStepSize, G4ForceCondition *condition)
Protected Member Functions inherited from G4VProcess
void	SubtractNumberOfInteractionLengthLeft (G4double previousStepSize)
void	ClearNumberOfInteractionLengthLeft ()

Additional Inherited Members
Static Public Member Functions inherited from G4VProcess
static const G4String &	GetProcessTypeName (G4ProcessType)
Protected Attributes inherited from G4VProcess
const G4ProcessManager *	aProcessManager
G4VParticleChange *	pParticleChange
G4ParticleChange	aParticleChange
G4double	theNumberOfInteractionLengthLeft
G4double	currentInteractionLength
G4double	theInitialNumberOfInteractionLength
G4String	theProcessName
G4String	thePhysicsTableFileName
G4ProcessType	theProcessType
G4int	theProcessSubType
G4double	thePILfactor
G4bool	enableAtRestDoIt
G4bool	enableAlongStepDoIt
G4bool	enablePostStepDoIt
G4int	verboseLevel

Detailed Description

Definition at line 62 of file G4LowEnergyGammaConversion.hh.

Constructor & Destructor Documentation

G4LowEnergyGammaConversion::G4LowEnergyGammaConversion

(

const G4String &

processName = "LowEnConversion"

)

Definition at line 78 of file G4LowEnergyGammaConversion.cc.

  : G4VDiscreteProcess(processName),
    lowEnergyLimit(1.022000*MeV),
    highEnergyLimit(100*GeV),
    intrinsicLowEnergyLimit(1.022000*MeV),
    intrinsicHighEnergyLimit(100*GeV),
    smallEnergy(2.*MeV)

{
  if (lowEnergyLimit < intrinsicLowEnergyLimit || 
      highEnergyLimit > intrinsicHighEnergyLimit)
    {
      G4Exception("G4LowEnergyGammaConversion::G4LowEnergyGammaConversion()",
                  "OutOfRange", FatalException,
                  "Energy limit outside intrinsic process validity range!");
    }

  // The following pointer is owned by G4DataHandler
  
  crossSectionHandler = new G4RDCrossSectionHandler();
  crossSectionHandler->Initialise(0,1.0220*MeV,100.*GeV,400);
  meanFreePathTable = 0;
  rangeTest = new G4RDRangeTest;

   if (verboseLevel > 0) 
     {
       G4cout << GetProcessName() << " is created " << G4endl
          << "Energy range: " 
          << lowEnergyLimit / MeV << " MeV - "
          << highEnergyLimit / GeV << " GeV" 
          << G4endl;
     }
}

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G4LowEnergyGammaConversion::~G4LowEnergyGammaConversion

(

)

Definition at line 112 of file G4LowEnergyGammaConversion.cc.

{
  delete meanFreePathTable;
  delete crossSectionHandler;
  delete rangeTest;
}

Member Function Documentation

void G4LowEnergyGammaConversion::BuildPhysicsTable ( const G4ParticleDefinition &  photon )

virtual

Reimplemented from G4VProcess.

Definition at line 119 of file G4LowEnergyGammaConversion.cc.

{

  crossSectionHandler->Clear();
  G4String crossSectionFile = "pair/pp-cs-";
  crossSectionHandler->LoadData(crossSectionFile);

  delete meanFreePathTable;
  meanFreePathTable = crossSectionHandler->BuildMeanFreePathForMaterials();
}

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G4double G4LowEnergyGammaConversion::DumpMeanFreePath ( const G4Track &  aTrack, G4double  previousStepSize, G4ForceCondition *  condition  )

inline

Definition at line 78 of file G4LowEnergyGammaConversion.hh.

  { return GetMeanFreePath(aTrack, previousStepSize, condition); }

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G4double G4LowEnergyGammaConversion::GetMeanFreePath ( const G4Track &  aTrack, G4double  previousStepSize, G4ForceCondition *  condition  )

protectedvirtual

Implements G4VDiscreteProcess.

Definition at line 319 of file G4LowEnergyGammaConversion.cc.

{
  const G4DynamicParticle* photon = track.GetDynamicParticle();
  G4double energy = photon->GetKineticEnergy();
  const G4MaterialCutsCouple* couple = track.GetMaterialCutsCouple();
  size_t materialIndex = couple->GetIndex();

  G4double meanFreePath;
  if (energy > highEnergyLimit) meanFreePath = meanFreePathTable->FindValue(highEnergyLimit,materialIndex);
  else if (energy < lowEnergyLimit) meanFreePath = DBL_MAX;
  else meanFreePath = meanFreePathTable->FindValue(energy,materialIndex);
  return meanFreePath;
}

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G4bool G4LowEnergyGammaConversion::IsApplicable ( const G4ParticleDefinition &  photon )

virtual

Reimplemented from G4VProcess.

Definition at line 314 of file G4LowEnergyGammaConversion.cc.

{
  return ( &particle == G4Gamma::Gamma() ); 
}

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G4VParticleChange * G4LowEnergyGammaConversion::PostStepDoIt ( const G4Track &  aTrack, const G4Step &  aStep  )

virtual

Reimplemented from G4VDiscreteProcess.

Definition at line 130 of file G4LowEnergyGammaConversion.cc.

{
// The energies of the e+ e- secondaries are sampled using the Bethe - Heitler
// cross sections with Coulomb correction. A modified version of the random
// number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15).

// Note 1 : Effects due to the breakdown of the Born approximation at low
// energy are ignored.
// Note 2 : The differential cross section implicitly takes account of
// pair creation in both nuclear and atomic electron fields. However triplet
// prodution is not generated.

  aParticleChange.Initialize(aTrack);

  const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple();

  const G4DynamicParticle* incidentPhoton = aTrack.GetDynamicParticle();
  G4double photonEnergy = incidentPhoton->GetKineticEnergy();
  G4ParticleMomentum photonDirection = incidentPhoton->GetMomentumDirection();

  G4double epsilon ;
  G4double epsilon0 = electron_mass_c2 / photonEnergy ;

  // Do it fast if photon energy < 2. MeV
  if (photonEnergy < smallEnergy )
    {
      epsilon = epsilon0 + (0.5 - epsilon0) * G4UniformRand();
    }
  else
    {
      // Select randomly one element in the current material
      const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy);

      if (element == 0)
    {
      G4cout << "G4LowEnergyGammaConversion::PostStepDoIt - element = 0" << G4endl;
    }
      G4IonisParamElm* ionisation = element->GetIonisation();
       if (ionisation == 0)
    {
      G4cout << "G4LowEnergyGammaConversion::PostStepDoIt - ionisation = 0" << G4endl;
    }

      // Extract Coulomb factor for this Element
      G4double fZ = 8. * (ionisation->GetlogZ3());
      if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb());

      // Limits of the screening variable
      G4double screenFactor = 136. * epsilon0 / (element->GetIonisation()->GetZ3()) ;
      G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ;
      G4double screenMin = std::min(4.*screenFactor,screenMax) ;

      // Limits of the energy sampling
      G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ;
      G4double epsilonMin = std::max(epsilon0,epsilon1);
      G4double epsilonRange = 0.5 - epsilonMin ;

      // Sample the energy rate of the created electron (or positron)
      G4double screen;
      G4double gReject ;

      G4double f10 = ScreenFunction1(screenMin) - fZ;
      G4double f20 = ScreenFunction2(screenMin) - fZ;
      G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.);
      G4double normF2 = std::max(1.5 * f20,0.);

      do {
    if (normF1 / (normF1 + normF2) > G4UniformRand() )
      {
        epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.3333) ;
        screen = screenFactor / (epsilon * (1. - epsilon));
        gReject = (ScreenFunction1(screen) - fZ) / f10 ;
      }
    else
      {
        epsilon = epsilonMin + epsilonRange * G4UniformRand();
        screen = screenFactor / (epsilon * (1 - epsilon));
        gReject = (ScreenFunction2(screen) - fZ) / f20 ;
      }
      } while ( gReject < G4UniformRand() );

    }   //  End of epsilon sampling

  // Fix charges randomly

  G4double electronTotEnergy;
  G4double positronTotEnergy;

  if (CLHEP::RandBit::shootBit())
    {
      electronTotEnergy = (1. - epsilon) * photonEnergy;
      positronTotEnergy = epsilon * photonEnergy;
    }
  else
    {
      positronTotEnergy = (1. - epsilon) * photonEnergy;
      electronTotEnergy = epsilon * photonEnergy;
    }

  // Scattered electron (positron) angles. ( Z - axis along the parent photon)
  // Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211),
  // derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977)

  G4double u;
  const G4double a1 = 0.625;
  G4double a2 = 3. * a1;
  //  G4double d = 27. ;

  //  if (9. / (9. + d) > G4UniformRand())
  if (0.25 > G4UniformRand())
    {
      u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ;
    }
  else
    {
      u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ;
    }

  G4double thetaEle = u*electron_mass_c2/electronTotEnergy;
  G4double thetaPos = u*electron_mass_c2/positronTotEnergy;
  G4double phi  = twopi * G4UniformRand();

  G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle);
  G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos);
  
  
  // Kinematics of the created pair:
  // the electron and positron are assumed to have a symetric angular 
  // distribution with respect to the Z axis along the parent photon
  
  G4double localEnergyDeposit = 0. ;
  
  aParticleChange.SetNumberOfSecondaries(2) ; 
  G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ;
  
  // Generate the electron only if with large enough range w.r.t. cuts and safety
  
  G4double safety = aStep.GetPostStepPoint()->GetSafety();
  
  if (rangeTest->Escape(G4Electron::Electron(),couple,electronKineEnergy,safety))
    {
      G4ThreeVector electronDirection (dxEle, dyEle, dzEle);
      electronDirection.rotateUz(photonDirection);
      
      G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(),
                                electronDirection,
                                electronKineEnergy);
      aParticleChange.AddSecondary(particle1) ;
    }
  else
    {
      localEnergyDeposit += electronKineEnergy ;
    }

  // The e+ is always created (even with kinetic energy = 0) for further annihilation
  G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;

  // Is the local energy deposit correct, if the positron is always created?
  if (! (rangeTest->Escape(G4Positron::Positron(),couple,positronKineEnergy,safety)))
    {
      localEnergyDeposit += positronKineEnergy ;
      positronKineEnergy = 0. ;
    }

  G4ThreeVector positronDirection (dxPos, dyPos, dzPos);
  positronDirection.rotateUz(photonDirection);   
  
  // Create G4DynamicParticle object for the particle2 
  G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(),
                               positronDirection, positronKineEnergy);
  aParticleChange.AddSecondary(particle2) ; 

  aParticleChange.ProposeLocalEnergyDeposit(localEnergyDeposit) ;
  
  // Kill the incident photon 
  aParticleChange.ProposeMomentumDirection(0.,0.,0.) ;
  aParticleChange.ProposeEnergy(0.) ; 
  aParticleChange.ProposeTrackStatus(fStopAndKill) ;

  //  Reset NbOfInteractionLengthLeft and return aParticleChange
  return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
}

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---

The documentation for this class was generated from the following files:

• source/geant4.10.03.p03/examples/advanced/eRosita/physics/include/G4LowEnergyGammaConversion.hh
• source/geant4.10.03.p03/examples/advanced/eRosita/physics/src/G4LowEnergyGammaConversion.cc