// 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: G4IeplusAnnihilation.icc,v 1.2 1999/12/15 14:51:46 gunter Exp $
// GEANT4 tag $Name: geant4-02-00 $
//
// $Id: 
// ---------------------------------------------------------------
//      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
//      ------------ G4IeplusAnnihilation process ---------
//                   by Michel Maire, 7 July 1996
// ***************************************************************
// ************************************************************
// It is the first implementation of the 
//          eplusANNIHILATION  PROCESS
//   using an INTEGRAL APPROACH instead of the differential
//   one used in the standard implementation .
// ************************************************************
//                by Laszlo Urban, 23 June 1998
// ---------------------------------------------------------
// 28/10/98:  some cleanup , L.Urban

inline G4bool G4IeplusAnnihilation::IsApplicable(const G4ParticleDefinition& particle)
{
   return ( &particle == G4Positron::Positron() ); 
}
inline G4double G4IeplusAnnihilation::GetMicroscopicCrossSection(
                                                     G4DynamicParticle* aDynamicPositron,
                                                     G4Element*         anElement)
 
// gives the microscopic total cross section in GEANT4 internal units

{
   G4double crossSection;
   G4double PositronEnergy = aDynamicPositron->GetKineticEnergy();
   G4bool isOutRange ;

   if (PositronEnergy > HighestEnergyLimit)
     crossSection = 0. ;
   else {
     if (PositronEnergy < LowestEnergyLimit) PositronEnergy = 1.01*LowestEnergyLimit;
     crossSection = (*theCrossSectionTable)(anElement->GetIndex())->
                    GetValue( PositronEnergy, isOutRange );
   }

   return crossSection; 
}


inline G4double G4IeplusAnnihilation::PostStepGetPhysicalInteractionLength(
                             const G4Track& track,
                             G4double   previousStepSize,
                             G4ForceCondition* condition
                            )
{// get particle,particle type,kin.energy,material,mat.index
  const G4double Tfac=0.95,Tfac1=1.-Tfac,eps=1.e-2  ;
  G4double nl,nll,nlold,range,rangeold,rangenext,
           dEdx,KineticEnergyOld,KineticEnergyNext,value;
  G4bool isOut;
  const G4DynamicParticle* particle = track.GetDynamicParticle();
  const G4ParticleDefinition* particletype = particle->GetDefinition() ;
  G4double KineticEnergy = particle->GetKineticEnergy();
  G4Material* material = track.GetMaterial();
  const G4MaterialTable* theMaterialTable =
                         G4Material::GetMaterialTable();
  G4int materialindex = material->GetIndex();

  nl = (*theNlambdaTable)[materialindex]->
                           GetValue(KineticEnergy,isOut);
  range = G4EnergyLossTables::GetPreciseRangeFromEnergy(particletype,
                                       KineticEnergy,material) ;

  if ( (previousStepSize <=0.0) || (theNumberOfInteractionLengthLeft<=0.0)) {
    ResetNumberOfInteractionLengthLeft();
  } else {
   if(previousStepSize/range < eps)
   {
    nll = (*theNlambdaTable)[materialindex]->
                             GetValue(Tfac*KineticEnergy,isOut) ;
    dEdx = G4EnergyLossTables::GetPreciseDEDX(particletype,
                                              KineticEnergy,
                                              material) ;
    nlold = nl + dEdx*previousStepSize*(nl-nll)/
                                  (Tfac1*KineticEnergy) ;
   }
   else
   {
    rangeold = range + previousStepSize ;
    KineticEnergyOld = G4EnergyLossTables::GetPreciseEnergyFromRange(
                                             particletype,
                                       rangeold,material);
    nlold = (*theNlambdaTable)[materialindex]->
                           GetValue(KineticEnergyOld,isOut);

    if(nlold < nl)
     {
     if(verboseLevel>2)
     {
      G4cout << "G4IeplusAnnihilation PostStepGPIL : Nlambda has been" <<
              " increased at update.Nlambda old/new :" << nlold <<
              "  " << nl << G4endl;
      G4cout << "(theNumberOfInteractionLengthLeft has been increased!)" << G4endl;
      G4cout << " correction : Nlambda old=new ........." << G4endl;
     }
      nlold = nl ;
     }
    }

    theNumberOfInteractionLengthLeft -= nlold-nl ;

    if(theNumberOfInteractionLengthLeft<perMillion)
       theNumberOfInteractionLengthLeft=0.;
  }


 // condition is set to "Not Forced"
  *condition = NotForced;
  if(nl <= theNumberOfInteractionLengthLeft)
  {
    value = DBL_MAX ;
  }
  else
  {
   if(theNumberOfInteractionLengthLeft/nl < eps)
   {
    nll = (*theNlambdaTable)[materialindex]->
                             GetValue(Tfac*KineticEnergy,isOut) ;
    dEdx = G4EnergyLossTables::GetPreciseDEDX(particletype,
                                              KineticEnergy,
                                              material) ;

    value = theNumberOfInteractionLengthLeft*Tfac1*KineticEnergy/(dEdx*(nl-nll)) ;
   }
   else
   {

    KineticEnergyNext = (*theInverseNlambdaTable)[materialindex]->
                        GetValue(nl-theNumberOfInteractionLengthLeft,isOut);
    rangenext = G4EnergyLossTables::GetPreciseRangeFromEnergy(particletype,
                                       KineticEnergyNext,material);

    value = range - rangenext ;

    if(range<rangenext)
    {
    if(verboseLevel>2)
    {
     G4cout << "G4IeplusAnnihilation PostStepGPIL: Step < 0.!, Step=" <<
             value << G4endl;
     G4cout << "range,rangenext:" << range << "  " << rangenext << G4endl ;
     G4cout << "correction : rangenext=range ....." << G4endl;
    }
     rangenext = range ;
     value = range - rangenext ;
    }
   }
  }
  return value;
}
 
inline G4double G4IeplusAnnihilation::ComputeMeanFreePath(G4double PositKinEnergy,
                                                       G4Material* aMaterial)

// returns the positron 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( PositKinEnergy,
                                                    (*theElementVector)(i)->GetZ() );
      }       

  return SIGMA<=0.0 ? DBL_MAX : 1./SIGMA ;
}

inline G4double G4IeplusAnnihilation::GetMeanLifeTime(const G4Track&,
                                                     G4ForceCondition*)
// returns the annihilation mean life time in GEANT4 internal units

{
   return 0.0; 
}