G4FissionParameters.cc

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//
//
// Hadronic Process: Nuclear De-excitations
// by V. Lara (Oct 1998)
//
//J. M. Quesada (May 2009): sigma_sym (SigmaS) tuned for spallation data.
//J. M. Quesada (30.10.09): retuning for IAEA spallation data

#include "G4FissionParameters.hh"
#include "G4SystemOfUnits.hh"

G4FissionParameters::G4FissionParameters()
  : A1(134),A2(141),A3((A1 + A2)*0.5),As(0.0),Sigma1(0.0),Sigma2(0.0),
    SigmaS(0.),w(0.0)
{}

G4FissionParameters::~G4FissionParameters()
{}

void G4FissionParameters::DefineParameters(G4int A, G4int Z, G4double ExEnergy,
             G4double FissionBarrier)
{
  // to avoid usage of units
  G4double U = std::min(200., ExEnergy/CLHEP::MeV); 

  As = A*0.5;
    
  if (A <= 235) { Sigma2 = 5.6; }  
  else          { Sigma2 = 5.6 + 0.096*(A-235); }

  Sigma1 = 0.5*Sigma2;     
    
  //JMQ 310509 
  //    if (SigmaS > 20.0) SigmaS = 20.0;
  //   SigmaS*=1.3;
  //JMQ 301009: retuning (after CEM transition prob.have been chosen as default)
  SigmaS = 0.8*G4Exp(0.00553*U + 2.1386); 
        
  G4double wa = 0.0;
  w = 0.0;
  if (Z >= 90) {  
    if (U <= 16.25) { wa = G4Exp(0.5385*U-9.9564); }  
    else            { wa = G4Exp(0.09197*U-2.7003); }            
  } else if (Z == 89) {  
    wa = G4Exp(0.09197*U-1.0808);
  } else if (Z >= 82) {  
    G4double X = std::max(0.0, FissionBarrier/CLHEP::MeV - 7.5);
    wa = G4Exp(0.09197*(U-X) - 1.0808);
  } else {               // Z < 82
    w = 1001.0;
  }
    
  if (Z >= 82) {
    G4double x1 = (A1-As)/Sigma1;
    G4double x2 = (A2-As)/Sigma2;
    G4double FasymAsym = 2*LocalExp(x2) + LocalExp(x1);
    
    G4double x3 = (As-A3)/SigmaS;
    G4double FsymA1A2 = LocalExp(x3);

    G4double w1 = std::max(1.03*wa - FasymAsym, 0.0001);
    G4double w2 = std::max(1.0 - FsymA1A2*wa,   0.0001);
    
    w = w1/w2;
      
    if (A < 227) { w *= G4Exp(0.3*(227-A)); }
  }
}