// This code implementation is the intellectual property of
// the GEANT4 collaboration.
//
// By copying, distributing or modifying the Program (or any work
// based on the Program) you indicate your acceptance of this statement,
// and all its terms.
//
// $Id: G4GammaConversion.icc,v 1.1.10.1 1999/12/07 20:50:48 gunter Exp $
// GEANT4 tag $Name: geant4-01-00 $
//
// 
// ---------------------------------------------------------------
//      GEANT 4 class inlined methods file
//
//      For information related to this code contact:
//      CERN, CN Division, ASD group
//      History: first implementation, based on object model of
//      2nd December 1995, G.Cosmo
//      ------------ G4GammaConversion physics process ---------
//                   by Michel Maire, 24 May 1996
// ***************************************************************
// 11-06-96, in GetMeanFreePath() the partial sum is stored, by M.Maire
// 16-09-96, dynamical array PartialSumSigma, by M.Maire
// 13-12-96, Sign corrected in the ScreenFunctions, by L.Urban
// 14-01-97, crossection table + meanfreepath table.
//           PartialSumSigma removed, by M.Maire
// 14-01-97, new physics scheme for geant4alpha, M.Maire
// ---------------------------------------------------------------

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

inline G4bool G4GammaConversion::IsApplicable(const G4ParticleDefinition& particle)
{
   return ( &particle == G4Gamma::Gamma() ); 
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

inline G4double G4GammaConversion::GetMicroscopicCrossSection(
                                   const G4DynamicParticle* aDynamicGamma,
                                         G4Element*         anElement)
 
// gives the microscopic total cross section in GEANT4 internal units

{
   G4double crossSection;
   G4double GammaEnergy = aDynamicGamma->GetKineticEnergy();
   G4bool isOutRange ;

   if (GammaEnergy <  LowestEnergyLimit)
     crossSection = 0. ;
   else {
     if (GammaEnergy > HighestEnergyLimit) GammaEnergy = 0.99*HighestEnergyLimit ;
     crossSection = (*theCrossSectionTable)(anElement->GetIndex())->
                    GetValue( GammaEnergy, isOutRange );
   }

   return crossSection; 
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
 
inline G4double G4GammaConversion::GetMeanFreePath(const G4Track& aTrack,
                                                     G4double,
                                                     G4ForceCondition*)

// returns the photon mean free path in GEANT4 internal units
// (MeanFreePath is a private member of the class)

{
   const G4DynamicParticle* aDynamicGamma = aTrack.GetDynamicParticle();
   G4double GammaEnergy = aDynamicGamma->GetKineticEnergy();
   G4Material* aMaterial = aTrack.GetMaterial();

   G4bool isOutRange ;

   if (GammaEnergy <  LowestEnergyLimit)
     MeanFreePath = DBL_MAX;
   else {
     if (GammaEnergy > HighestEnergyLimit) GammaEnergy = 0.99*HighestEnergyLimit ;
     MeanFreePath = (*theMeanFreePathTable)(aMaterial->GetIndex())->
                    GetValue( GammaEnergy, isOutRange );
   }

   return MeanFreePath; 
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

inline G4double G4GammaConversion::ComputeMeanFreePath(G4double GammaEnergy,
                                                       G4Material* aMaterial)

// computes and returns the photon mean free path in GEANT4 internal units

{
  const G4ElementVector* theElementVector = aMaterial->GetElementVector() ;
  const G4double* theAtomNumDensityVector = aMaterial->GetAtomicNumDensityVector();   

  G4double SIGMA = 0 ;

  for ( G4int i=0 ; i < aMaterial->GetNumberOfElements() ; i++ )
      {             
            SIGMA += theAtomNumDensityVector[i] * 
                     ComputeMicroscopicCrossSection(GammaEnergy,
                                                   (*theElementVector)(i)->GetZ() );
      }       

  return SIGMA > DBL_MIN ? 1./SIGMA : DBL_MAX;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

inline G4double G4GammaConversion::ScreenFunction1(G4double ScreenVariable)

// compute the value of the screening function 3*PHI1 - PHI2

{
   G4double screenVal;

   if (ScreenVariable > 1.)
     screenVal = 42.24 - 8.368*log(ScreenVariable+0.952);
   else
     screenVal = 42.392 - ScreenVariable* (7.796 - 1.961*ScreenVariable);

   return screenVal;
} 

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....

inline G4double G4GammaConversion::ScreenFunction2(G4double ScreenVariable)

// compute the value of the screening function 1.5*PHI1 - 0.5*PHI2

{
   G4double screenVal;

   if (ScreenVariable > 1.)
     screenVal = 42.24 - 8.368*log(ScreenVariable+0.952);
   else
     screenVal = 41.405 - ScreenVariable* (5.828 - 0.8945*ScreenVariable);

   return screenVal;
} 

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
