G4FissionProbability.cc

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//
//
// Hadronic Process: Nuclear De-excitations
// by V. Lara (Oct 1998)
//
//
// J.M.Quesada (14 february 2009) bug fixed in fission width: missing 
//                                parenthesis in the denominator 


#include "G4FissionProbability.hh"
#include "G4PhysicalConstants.hh"
#include "G4NuclearLevelData.hh"
#include "G4PairingCorrection.hh"
#include "G4EvaporationLevelDensityParameter.hh"
#include "G4FissionLevelDensityParameter.hh"
#include "G4Exp.hh"

G4FissionProbability::G4FissionProbability() :
  G4VEmissionProbability(0, 0),
  theEvapLDP(new G4EvaporationLevelDensityParameter),
  theFissLDP(new G4FissionLevelDensityParameter),
  ownEvapLDP(true),
  ownFissLDP(true)
{
  fPairCorr = G4NuclearLevelData::GetInstance()->GetPairingCorrection();
}

G4FissionProbability::~G4FissionProbability()
{
  if (ownEvapLDP) delete theEvapLDP;
  if (ownFissLDP) delete theFissLDP;
}

G4double 
G4FissionProbability::EmissionProbability(const G4Fragment & fragment, 
            G4double MaximalKineticEnergy)
  // Compute integrated probability of fission channel
{
  if (MaximalKineticEnergy <= 0.0) { return 0.0; }
  G4int A = fragment.GetA_asInt();
  G4int Z = fragment.GetZ_asInt();
  G4double U = fragment.GetExcitationEnergy();
  
  G4double Ucompound = U - fPairCorr->GetPairingCorrection(A,Z);
  G4double Ufission = U - fPairCorr->GetFissionPairingCorrection(A,Z);
  if(Ucompound < 0.0 || Ufission < 0.0) { return 0.0; }
  
  G4double SystemEntropy = 
    2.0*std::sqrt(theEvapLDP->LevelDensityParameter(A,Z,Ucompound)*Ucompound);
  
  G4double afission = theFissLDP->LevelDensityParameter(A,Z,Ufission);

  G4double Cf = 2.0*std::sqrt(afission*MaximalKineticEnergy);
  G4double Exp1 = (SystemEntropy <= 160.0) ? G4Exp(-SystemEntropy) : 0.0; 
  G4double Exp2 = (SystemEntropy-Cf <= 160.0) ? G4Exp(-SystemEntropy+Cf) : 0.0; 

  // JMQ 14/02/09 BUG fixed in fission probability (missing parenthesis 
  // at denominator)
  G4double probability = (Exp1 + (Cf-1.0)*Exp2) / (4.0*pi*afission);

  return probability;
}