G4LowEnergyCompton Class Reference

#include <G4LowEnergyCompton.hh>

Inheritance diagram for G4LowEnergyCompton:

Public Member Functions
	G4LowEnergyCompton (const G4String &processName="LowEnCompton")
	~G4LowEnergyCompton ()
G4bool	IsApplicable (const G4ParticleDefinition &definition)
void	BuildPhysicsTable (const G4ParticleDefinition &definition)
G4VParticleChange *	PostStepDoIt (const G4Track &track, const G4Step &step)
G4double	DumpMeanFreePath (const G4Track &track, 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 &track, 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 61 of file G4LowEnergyCompton.hh.

Constructor & Destructor Documentation

G4LowEnergyCompton::G4LowEnergyCompton

(

const G4String &

processName = "LowEnCompton"

)

Definition at line 73 of file G4LowEnergyCompton.cc.

References FatalException, G4cout, G4endl, G4Exception(), G4VProcess::GetProcessName(), python.hepunit::GeV, python.hepunit::keV, G4RDVEMDataSet::LoadData(), G4RDShellData::SetOccupancyData(), and G4VProcess::verboseLevel.

  : G4VDiscreteProcess(processName),
    lowEnergyLimit(250*eV),
    highEnergyLimit(100*GeV),
    intrinsicLowEnergyLimit(10*eV),
    intrinsicHighEnergyLimit(100*GeV)
{
  if (lowEnergyLimit < intrinsicLowEnergyLimit ||
      highEnergyLimit > intrinsicHighEnergyLimit)
    {
      G4Exception("G4LowEnergyCompton::G4LowEnergyCompton()",
                  "OutOfRange", FatalException,
                  "Energy outside intrinsic process validity range!");
    }

  crossSectionHandler = new G4RDCrossSectionHandler;

  G4RDVDataSetAlgorithm* scatterInterpolation = new G4RDLogLogInterpolation;
  G4String scatterFile = "comp/ce-sf-";
  scatterFunctionData = new G4RDCompositeEMDataSet(scatterInterpolation, 1., 1.);
  scatterFunctionData->LoadData(scatterFile);

  meanFreePathTable = 0;

  rangeTest = new G4RDRangeNoTest;

  // For Doppler broadening
  shellData.SetOccupancyData();

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

G4LowEnergyCompton::~G4LowEnergyCompton

(

)

Definition at line 112 of file G4LowEnergyCompton.cc.

{
  delete meanFreePathTable;
  delete crossSectionHandler;
  delete scatterFunctionData;
  delete rangeTest;
}

Member Function Documentation

void G4LowEnergyCompton::BuildPhysicsTable ( const G4ParticleDefinition &  definition )

virtual

Reimplemented from G4VProcess.

Definition at line 120 of file G4LowEnergyCompton.cc.

References G4RDVCrossSectionHandler::BuildMeanFreePathForMaterials(), G4RDVCrossSectionHandler::Clear(), G4RDShellData::LoadData(), and G4RDVCrossSectionHandler::LoadData().

{

  crossSectionHandler->Clear();
  G4String crossSectionFile = "comp/ce-cs-";
  crossSectionHandler->LoadData(crossSectionFile);

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

  // For Doppler broadening
  G4String file = "/doppler/shell-doppler";
  shellData.LoadData(file);
}

G4double G4LowEnergyCompton::DumpMeanFreePath ( const G4Track &  track, G4double  previousStepSize, G4ForceCondition *  condition  )

inline

Definition at line 76 of file G4LowEnergyCompton.hh.

References GetMeanFreePath().

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

G4double G4LowEnergyCompton::GetMeanFreePath ( const G4Track &  track, G4double  previousStepSize, G4ForceCondition *  condition  )

protectedvirtual

Implements G4VDiscreteProcess.

Definition at line 331 of file G4LowEnergyCompton.cc.

References DBL_MAX, energy(), G4RDVEMDataSet::FindValue(), G4Track::GetDynamicParticle(), G4MaterialCutsCouple::GetIndex(), G4DynamicParticle::GetKineticEnergy(), G4Track::GetMaterialCutsCouple(), and photon.

Referenced by DumpMeanFreePath().

{
  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;
}

G4bool G4LowEnergyCompton::IsApplicable ( const G4ParticleDefinition &  definition )

virtual

Reimplemented from G4VProcess.

Definition at line 326 of file G4LowEnergyCompton.cc.

References G4Gamma::Gamma().

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

G4VParticleChange * G4LowEnergyCompton::PostStepDoIt ( const G4Track &  track, const G4Step &  step  )

virtual

Reimplemented from G4VDiscreteProcess.

Definition at line 135 of file G4LowEnergyCompton.cc.

References G4ParticleChange::AddSecondary(), G4VProcess::aParticleChange, G4RDShellData::BindingEnergy(), python.hepunit::c_light, python.hepunit::cm, G4InuclParticleNames::electron, G4Electron::Electron(), python.hepunit::electron_mass_c2, python.hepunit::epsilon0, G4RDVRangeTest::Escape(), G4RDVEMDataSet::FindValue(), python.hepunit::fine_structure_const, fStopAndKill, G4UniformRand, G4Track::GetDynamicParticle(), G4DynamicParticle::GetKineticEnergy(), G4Track::GetMaterialCutsCouple(), G4DynamicParticle::GetMomentumDirection(), G4Step::GetPostStepPoint(), G4StepPoint::GetSafety(), python.hepunit::h_Planck, G4ParticleChange::Initialize(), G4VDiscreteProcess::PostStepDoIt(), G4ParticleChange::ProposeEnergy(), G4VParticleChange::ProposeLocalEnergyDeposit(), G4ParticleChange::ProposeMomentumDirection(), G4VParticleChange::ProposeTrackStatus(), G4RDDopplerProfile::RandomSelectMomentum(), CLHEP::Hep3Vector::rotateUz(), G4RDVCrossSectionHandler::SelectRandomAtom(), G4RDShellData::SelectRandomShell(), G4VParticleChange::SetNumberOfSecondaries(), python.hepunit::twopi, var(), and test::x.

{
  // The scattered gamma energy is sampled according to Klein - Nishina formula.
  // then accepted or rejected depending on the Scattering Function multiplied
  // by factor from Klein - Nishina formula.
  // Expression of the angular distribution as Klein Nishina
  // angular and energy distribution and Scattering fuctions is taken from
  // D. E. Cullen "A simple model of photon transport" Nucl. Instr. Meth.
  // Phys. Res. B 101 (1995). Method of sampling with form factors is different
  // data are interpolated while in the article they are fitted.
  // Reference to the article is from J. Stepanek New Photon, Positron
  // and Electron Interaction Data for GEANT in Energy Range from 1 eV to 10
  // TeV (draft).
  // The random number techniques of Butcher & Messel are used
  // (Nucl Phys 20(1960),15).

  aParticleChange.Initialize(aTrack);

  // Dynamic particle quantities
  const G4DynamicParticle* incidentPhoton = aTrack.GetDynamicParticle();
  G4double photonEnergy0 = incidentPhoton->GetKineticEnergy();

  if (photonEnergy0 <= lowEnergyLimit)
    {
      aParticleChange.ProposeTrackStatus(fStopAndKill);
      aParticleChange.ProposeEnergy(0.);
      aParticleChange.ProposeLocalEnergyDeposit(photonEnergy0);
      return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
    }

  G4double e0m = photonEnergy0 / electron_mass_c2 ;
  G4ParticleMomentum photonDirection0 = incidentPhoton->GetMomentumDirection();
  G4double epsilon0 = 1. / (1. + 2. * e0m);
  G4double epsilon0Sq = epsilon0 * epsilon0;
  G4double alpha1 = -std::log(epsilon0);
  G4double alpha2 = 0.5 * (1. - epsilon0Sq);
  G4double wlPhoton = h_Planck*c_light/photonEnergy0;

  // Select randomly one element in the current material
  const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple();
  G4int Z = crossSectionHandler->SelectRandomAtom(couple,photonEnergy0);

  // Sample the energy of the scattered photon
  G4double epsilon;
  G4double epsilonSq;
  G4double oneCosT;
  G4double sinT2;
  G4double gReject;
  do
    {
      if ( alpha1/(alpha1+alpha2) > G4UniformRand())
    {
      epsilon = std::exp(-alpha1 * G4UniformRand());  // std::pow(epsilon0,G4UniformRand())
      epsilonSq = epsilon * epsilon;
    }
      else
    {
      epsilonSq = epsilon0Sq + (1. - epsilon0Sq) * G4UniformRand();
      epsilon = std::sqrt(epsilonSq);
    }

      oneCosT = (1. - epsilon) / ( epsilon * e0m);
      sinT2 = oneCosT * (2. - oneCosT);
      G4double x = std::sqrt(oneCosT/2.) / (wlPhoton/cm);
      G4double scatteringFunction = scatterFunctionData->FindValue(x,Z-1);
      gReject = (1. - epsilon * sinT2 / (1. + epsilonSq)) * scatteringFunction;

    }  while(gReject < G4UniformRand()*Z);

  G4double cosTheta = 1. - oneCosT;
  G4double sinTheta = std::sqrt (sinT2);
  G4double phi = twopi * G4UniformRand() ;
  G4double dirX = sinTheta * std::cos(phi);
  G4double dirY = sinTheta * std::sin(phi);
  G4double dirZ = cosTheta ;

  // Doppler broadening -  Method based on:
  // Y. Namito, S. Ban and H. Hirayama, 
  // "Implementation of the Doppler Broadening of a Compton-Scattered Photon Into the EGS4 Code" 
  // NIM A 349, pp. 489-494, 1994
  
  // Maximum number of sampling iterations
  G4int maxDopplerIterations = 1000;
  G4double bindingE = 0.;
  G4double photonEoriginal = epsilon * photonEnergy0;
  G4double photonE = -1.;
  G4int iteration = 0;
  G4double eMax = photonEnergy0;
  do
    {
      iteration++;
      // Select shell based on shell occupancy
      G4int shell = shellData.SelectRandomShell(Z);
      bindingE = shellData.BindingEnergy(Z,shell);
      
      eMax = photonEnergy0 - bindingE;
     
      // Randomly sample bound electron momentum (memento: the data set is in Atomic Units)
      G4double pSample = profileData.RandomSelectMomentum(Z,shell);
      // Rescale from atomic units
      G4double pDoppler = pSample * fine_structure_const;
      G4double pDoppler2 = pDoppler * pDoppler;
      G4double var2 = 1. + oneCosT * e0m;
      G4double var3 = var2*var2 - pDoppler2;
      G4double var4 = var2 - pDoppler2 * cosTheta;
      G4double var = var4*var4 - var3 + pDoppler2 * var3;
      if (var > 0.)
    {
      G4double varSqrt = std::sqrt(var);        
      G4double scale = photonEnergy0 / var3;  
          // Random select either root
      if (G4UniformRand() < 0.5) photonE = (var4 - varSqrt) * scale;               
      else photonE = (var4 + varSqrt) * scale;
    } 
      else
    {
      photonE = -1.;
    }
   } while ( iteration <= maxDopplerIterations && 
         (photonE < 0. || photonE > eMax || photonE < eMax*G4UniformRand()) );
 
  // End of recalculation of photon energy with Doppler broadening
  // Revert to original if maximum number of iterations threshold has been reached
  if (iteration >= maxDopplerIterations)
    {
      photonE = photonEoriginal;
      bindingE = 0.;
    }

  // Update G4VParticleChange for the scattered photon

  G4ThreeVector photonDirection1(dirX,dirY,dirZ);
  photonDirection1.rotateUz(photonDirection0);
  aParticleChange.ProposeMomentumDirection(photonDirection1);
 
  G4double photonEnergy1 = photonE;
  //G4cout << "--> PHOTONENERGY1 = " << photonE/keV << G4endl;

  if (photonEnergy1 > 0.)
    {
      aParticleChange.ProposeEnergy(photonEnergy1) ;
    }
  else
    {
      aParticleChange.ProposeEnergy(0.) ;
      aParticleChange.ProposeTrackStatus(fStopAndKill);
    }

  // Kinematics of the scattered electron
  G4double eKineticEnergy = photonEnergy0 - photonEnergy1 - bindingE;
  G4double eTotalEnergy = eKineticEnergy + electron_mass_c2;

  G4double electronE = photonEnergy0 * (1. - epsilon) + electron_mass_c2; 
  G4double electronP2 = electronE*electronE - electron_mass_c2*electron_mass_c2;
  G4double sinThetaE = -1.;
  G4double cosThetaE = 0.;
  if (electronP2 > 0.)
    {
      cosThetaE = (eTotalEnergy + photonEnergy1 )* (1. - epsilon) / std::sqrt(electronP2);
      sinThetaE = -1. * std::sqrt(1. - cosThetaE * cosThetaE); 
    }
  
  G4double eDirX = sinThetaE * std::cos(phi);
  G4double eDirY = sinThetaE * std::sin(phi);
  G4double eDirZ = cosThetaE;

  // 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,eKineticEnergy,safety))
    {
      G4ThreeVector eDirection(eDirX,eDirY,eDirZ);
      eDirection.rotateUz(photonDirection0);

      G4DynamicParticle* electron = new G4DynamicParticle (G4Electron::Electron(),eDirection,eKineticEnergy) ;
      aParticleChange.SetNumberOfSecondaries(1);
      aParticleChange.AddSecondary(electron);
      // Binding energy deposited locally
      aParticleChange.ProposeLocalEnergyDeposit(bindingE);
    }
  else
    {
      aParticleChange.SetNumberOfSecondaries(0);
      aParticleChange.ProposeLocalEnergyDeposit(eKineticEnergy + bindingE);
    }

  return G4VDiscreteProcess::PostStepDoIt( aTrack, aStep);
}

---

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

• G4LowEnergyCompton.hh
• G4LowEnergyCompton.cc