//
// ********************************************************************
// * DISCLAIMER                                                       *
// *                                                                  *
// * The following disclaimer summarizes all the specific disclaimers *
// * of contributors to this software. The specific disclaimers,which *
// * govern, are listed with their locations in:                      *
// *   http://cern.ch/geant4/license                                  *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.                                                             *
// *                                                                  *
// * 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 1.7 2001/09/17 17:07:11 maire Exp $
// GEANT4 tag $Name: geant4-04-01 $
//
// 
//      ------------ 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
// 28-05-01, V.Ivanchenko minor changes to provide ANSI -wall compilation
// 17-09-01, migration of Materials to pure STL (mma)  
// -----------------------------------------------------------------------------

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

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

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

inline G4double G4GammaConversion::GetCrossSectionPerAtom(
                                   const G4DynamicParticle* aDynamicGamma,
                                         G4Element*         anElement)
 
// gives the total cross section per atom 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* NbOfAtomsPerVolume = aMaterial->GetVecNbOfAtomsPerVolume();   

  G4double SIGMA = 0 ;

  for ( size_t i=0 ; i < aMaterial->GetNumberOfElements() ; i++ )
      {             
            SIGMA += NbOfAtomsPerVolume[i] * 
                     ComputeCrossSectionPerAtom(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......