G4RToEConvForGamma.cc

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//
// G4RToEConvForGamma class implementation
//
// Author: H.Kurashige, 05 October 2002 - First implementation
// --------------------------------------------------------------------
 
#include "G4RToEConvForGamma.hh"
#include "G4ParticleDefinition.hh"
#include "G4ParticleTable.hh"
#include "G4Material.hh"
#include "G4PhysicsLogVector.hh"
 
#include "G4ios.hh"
#include "G4SystemOfUnits.hh"
 
// --------------------------------------------------------------------
G4RToEConvForGamma::G4RToEConvForGamma()  
  : G4VRangeToEnergyConverter()
{    
  theParticle = G4ParticleTable::GetParticleTable()->FindParticle("gamma");
  if (theParticle == nullptr)
  {
#ifdef G4VERBOSE
    if (GetVerboseLevel()>0)
    {
      G4cout << " G4RToEConvForGamma::G4RToEConvForGamma() - ";
      G4cout << "Gamma is not defined !!" << G4endl;
    }
#endif
  } 
}
 
G4RToEConvForGamma::~G4RToEConvForGamma()
{ 
}
 
// ***********************************************************************
// ******************* BuildAbsorptionLengthVector ***********************
// ***********************************************************************
void G4RToEConvForGamma::BuildAbsorptionLengthVector(
                            const G4Material* aMaterial,
                            G4RangeVector* absorptionLengthVector )
{
  // fill the absorption length vector for this material
  // absorption length is defined here as:
  //   absorption length = 5./ macroscopic absorption cross section
  //
  const G4CrossSectionTable* aCrossSectionTable
        = (G4CrossSectionTable*)(theLossTable);
  const G4ElementVector* elementVector
        = aMaterial->GetElementVector();
  const G4double* atomicNumDensityVector
        = aMaterial->GetAtomicNumDensityVector();
 
  // fill absorption length vector
  G4int NumEl = aMaterial->GetNumberOfElements();
  G4double absorptionLengthMax = 0.0;
  for (std::size_t ibin=0; ibin<size_t(TotBin); ++ibin)
  {
    G4double SIGMA = 0.;
    for (std::size_t iel=0; iel<size_t(NumEl); ++iel)
    {
      G4int IndEl = (*elementVector)[iel]->GetIndex();
      SIGMA += atomicNumDensityVector[iel]
             * (*((*aCrossSectionTable)[IndEl]))[ibin];
    }
    //  absorption length=5./SIGMA
    absorptionLengthVector->PutValue(ibin, 5./SIGMA);
    if (absorptionLengthMax < 5./SIGMA )
      absorptionLengthMax = 5./SIGMA;
  }
}
 
// ***********************************************************************
// ********************** ComputeCrossSection ****************************
// ***********************************************************************
G4double G4RToEConvForGamma::ComputeCrossSection(G4double AtomicNumber,
                                                 G4double KineticEnergy) 
{
  // Compute the "absorption" cross-section of the photon "absorption".
  // Cross-section means here the sum of the cross-sections of the
  // pair production, Compton scattering and photoelectric processes
 
  const  G4double t1keV = 1.*keV;
  const  G4double t200keV = 200.*keV;
  const  G4double t100MeV = 100.*MeV;
 
  // Compute Z dependent quantities in the case of a new AtomicNumber
  if(std::abs(AtomicNumber-Z)>0.1)
  {
    Z = AtomicNumber;
    G4double Zsquare = Z*Z;
    G4double Zlog = std::log(Z);
    G4double Zlogsquare = Zlog*Zlog;
 
    s200keV = (0.2651-0.1501*Zlog+0.02283*Zlogsquare)*Zsquare;
    tmin = (0.552+218.5/Z+557.17/Zsquare)*MeV;
    smin = (0.01239+0.005585*Zlog-0.000923*Zlogsquare)*std::exp(1.5*Zlog);
    cmin = std::log(s200keV/smin)
         /(std::log(tmin/t200keV)*std::log(tmin/t200keV));
    tlow = 0.2*std::exp(-7.355/std::sqrt(Z))*MeV;
    slow = s200keV
         * std::exp(0.042*Z*std::log(t200keV/tlow)*std::log(t200keV/tlow));
    s1keV = 300.*Zsquare;
    clow = std::log(s1keV/slow)/std::log(tlow/t1keV);
    chigh = (7.55e-5-0.0542e-5*Z)*Zsquare*Z/std::log(t100MeV/tmin);
  }
 
  // Calculate the cross-section (using an approximate empirical formula)
  G4double xs;
  if ( KineticEnergy<tlow )
  {
    if(KineticEnergy<t1keV) xs = slow*std::exp(clow*std::log(tlow/t1keV));
    else  xs = slow*std::exp(clow*std::log(tlow/KineticEnergy));
  }
  else if ( KineticEnergy<t200keV )
  {
    xs = s200keV
       * std::exp(0.042*Z*std::log(t200keV/KineticEnergy)
                         *std::log(t200keV/KineticEnergy));
  }
  else if( KineticEnergy<tmin )
  {
    xs = smin
       * std::exp(cmin*std::log(tmin/KineticEnergy)
                      *std::log(tmin/KineticEnergy));
  }
  else
  {
    xs = smin + chigh*std::log(KineticEnergy/tmin);
  }
  return xs * barn;
}