G4GEMProbability.cc

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// $Id: G4GEMProbability.cc 74869 2013-10-23 09:26:17Z gcosmo $
//
//---------------------------------------------------------------------
//
// Geant4 class G4GEMProbability
//
//
// Hadronic Process: Nuclear De-excitations
// by V. Lara (Sept 2001) 
//
//
// Hadronic Process: Nuclear De-excitations
// by V. Lara (Sept 2001)
//
// J. M. Quesada : several fixes in total GEM width 
// J. M. Quesada 14/07/2009 bug fixed in total emission width (hbarc)
// J. M. Quesada (September 2009) several fixes:
//       -level density parameter of residual calculated at its right excitation energy.
//       -InitialLeveldensity calculated according to the right conditions of the 
//        initial excited nucleus.
// J. M. Quesada 19/04/2010 fix in  emission probability calculation.
// V.Ivanchenko  20/04/2010 added usage of G4Pow and use more safe computation
// V.Ivanchenko 18/05/2010 trying to speedup the most slow method
//            by usage of G4Pow, integer Z and A; moved constructor, 
//            destructor and virtual functions to source

#include "G4GEMProbability.hh"
#include "G4PairingCorrection.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4Log.hh"
#include "G4Exp.hh"

G4GEMProbability:: G4GEMProbability(G4int anA, G4int aZ, G4double aSpin) : 
  theA(anA), theZ(aZ), Spin(aSpin), theCoulombBarrierPtr(0), 
  Normalization(1.0)
{
  theEvapLDPptr = new G4EvaporationLevelDensityParameter;
  fG4pow = G4Pow::GetInstance(); 
  fPlanck= CLHEP::hbar_Planck*fG4pow->logZ(2);
  fPairCorr = G4PairingCorrection::GetInstance();
}
    
G4GEMProbability::~G4GEMProbability()
{
  delete theEvapLDPptr;
}

G4double G4GEMProbability::EmissionProbability(const G4Fragment & fragment,
                                               G4double MaximalKineticEnergy)
{
  G4double probability = 0.0;
    
  if (MaximalKineticEnergy > 0.0 && fragment.GetExcitationEnergy() > 0.0) {
    G4double CoulombBarrier = GetCoulombBarrier(fragment);
      
    probability = 
      CalcProbability(fragment,MaximalKineticEnergy,CoulombBarrier);

    // Next there is a loop over excited states for this channel 
    // summing probabilities
    size_t nn = ExcitEnergies.size();
    if (0 < nn) {
      G4double SavedSpin = Spin;
      for (size_t i = 0; i <nn; ++i) {
    Spin = ExcitSpins[i];
    // substract excitation energies
    G4double Tmax = MaximalKineticEnergy - ExcitEnergies[i];
    if (Tmax > 0.0) {
      G4double width = CalcProbability(fragment,Tmax,CoulombBarrier);
      //JMQ April 2010 added condition to prevent reported crash
      // update probability
      if (width > 0. && fPlanck < width*ExcitLifetimes[i]) {
        probability += width;
      }
    }
      }
      // Restore Spin
      Spin = SavedSpin;
    }
  }
  Normalization = probability;
  return probability;
}


G4double G4GEMProbability::CalcProbability(const G4Fragment & fragment, 
                                           G4double MaximalKineticEnergy,
                                           G4double V)

// Calculate integrated probability (width) for evaporation channel
{
  G4int A = fragment.GetA_asInt();
  G4int Z = fragment.GetZ_asInt();

  G4int ResidualA = A - theA;
  G4int ResidualZ = Z - theZ;
  G4double U = fragment.GetExcitationEnergy();
  
  G4double NuclearMass = fragment.ComputeGroundStateMass(theZ, theA);
  
  G4double Alpha = CalcAlphaParam(fragment);
  G4double Beta = CalcBetaParam(fragment);
    
  //                       ***RESIDUAL***
  //JMQ (September 2009) the following quantities refer to the RESIDUAL:
  
  G4double delta0 = fPairCorr->GetPairingCorrection(ResidualA, ResidualZ);  
  
  G4double a = theEvapLDPptr->
    LevelDensityParameter(ResidualA,ResidualZ,MaximalKineticEnergy+V-delta0);
  G4double Ux = (2.5 + 150.0/G4double(ResidualA))*MeV;
  G4double Ex = Ux + delta0;
  G4double T  = 1.0/(std::sqrt(a/Ux) - 1.5/Ux);
  //JMQ fixed bug in units
  G4double E0 = Ex - T*(G4Log(T/MeV) - G4Log(a*MeV)/4.0 
    - 1.25*G4Log(Ux/MeV) + 2.0*std::sqrt(a*Ux));
  //                      ***end RESIDUAL ***
  
  //                       ***PARENT***
  //JMQ (September 2009) the following quantities refer to the PARENT:
     
  G4double deltaCN = fPairCorr->GetPairingCorrection(A, Z);                    
  G4double aCN     = theEvapLDPptr->LevelDensityParameter(A, Z, U-deltaCN);
  G4double UxCN    = (2.5 + 150.0/G4double(A))*MeV;
  G4double ExCN    = UxCN + deltaCN;
  G4double TCN     = 1.0/(std::sqrt(aCN/UxCN) - 1.5/UxCN);
  //                     ***end PARENT***

  G4double Width;
  G4double InitialLevelDensity;
  G4double t = MaximalKineticEnergy/T;
  if ( MaximalKineticEnergy < Ex ) {
    //JMQ 190709 bug in I1 fixed (T was  missing)
    Width = (I1(t,t)*T + (Beta+V)*I0(t))/G4Exp(E0/T);
    //JMQ 160909 fix:  InitialLevelDensity has been taken away 
    //(different conditions for initial CN..) 
  } else {

    //VI minor speedup
    G4double expE0T = G4Exp(E0/T);
    static const G4double sqrt2 = std::sqrt(2.0);

    G4double tx = Ex/T;
    G4double s0 = 2.0*std::sqrt(a*(MaximalKineticEnergy-delta0));
    G4double sx = 2.0*std::sqrt(a*(Ex-delta0));
    Width = I1(t,tx)*T/expE0T + I3(s0,sx)*G4Exp(s0)/(sqrt2*a);
    // For charged particles (Beta+V) = 0 beacuse Beta = -V
    if (theZ == 0) {
      Width += (Beta+V)*(I0(tx)/expE0T + 2.0*sqrt2*I2(s0,sx)*G4Exp(s0));
    }
  }
  
  //JMQ 14/07/2009 BIG BUG : NuclearMass is in MeV => hbarc instead of hbar_planck must be used
  //    G4double g = (2.0*Spin+1.0)*NuclearMass/(pi2* hbar_Planck*hbar_Planck);
  G4double gg = (2.0*Spin+1.0)*NuclearMass/(pi2* hbarc*hbarc);
  
  //JMQ 190709 fix on Rb and  geometrical cross sections according to Furihata's paper 
  //                      (JAERI-Data/Code 2001-105, p6)
  //    G4double RN = 0.0;
  G4double Rb = 0.0;
  if (theA > 4) 
    {
      G4double Ad = fG4pow->Z13(ResidualA);
      G4double Aj = fG4pow->Z13(theA);
      Rb = 1.12*(Aj + Ad) - 0.86*((Aj+Ad)/(Aj*Ad))+2.85;
      Rb *= fermi;
    }
  else if (theA>1)
    {
      G4double Ad = fG4pow->Z13(ResidualA);
      G4double Aj = fG4pow->Z13(theA);
      Rb=1.5*(Aj+Ad)*fermi;
    }
  else
    {
      G4double Ad = fG4pow->Z13(ResidualA);
      Rb = 1.5*Ad*fermi;
    }
  //   G4double GeometricalXS = pi*RN*RN*std::pow(ResidualA,2./3.); 
  G4double GeometricalXS = pi*Rb*Rb; 
  //end of JMQ fix on Rb by 190709
  
  //JMQ 160909 fix: initial level density must be calculated according to the 
  // conditions at the initial compound nucleus 
  // (it has been removed from previous "if" for the residual) 

  if ( U < ExCN ) 
    {
      //JMQ fixed bug in units
      //VI moved the computation here
      G4double E0CN = ExCN - TCN*(G4Log(TCN/MeV) - G4Log(aCN*MeV)/4.0 
                  - 1.25*G4Log(UxCN/MeV) 
                  + 2.0*std::sqrt(aCN*UxCN));
      InitialLevelDensity = (pi/12.0)*G4Exp((U-E0CN)/TCN)/TCN;
    } 
  else 
    {
      //VI speedup
      G4double x  = U-deltaCN;
      G4double x1 = std::sqrt(aCN*x);
      InitialLevelDensity = (pi/12.0)*G4Exp(2*x1)/(x*std::sqrt(x1));
    }

  //JMQ 190709 BUG : pi instead of sqrt(pi) must be here according 
  // to Furihata's report:
  Width *= pi*gg*GeometricalXS*Alpha/(12.0*InitialLevelDensity); 
   
  return Width;
}

G4double G4GEMProbability::I3(G4double s0, G4double sx)
{
  G4double s2 = s0*s0;
  G4double sx2 = sx*sx;
  G4double S = 1.0/std::sqrt(s0);
  G4double S2 = S*S;
  G4double Sx = 1.0/std::sqrt(sx);
  G4double Sx2 = Sx*Sx;
  
  G4double p1 = S *(2.0 + S2 *( 4.0 + S2 *( 13.5 + S2 *( 60.0 + S2 * 325.125 ))));
  G4double p2 = Sx*Sx2 *(
             (s2-sx2) + Sx2 *(
                      (1.5*s2+0.5*sx2) + Sx2 *(
                                   (3.75*s2+0.25*sx2) + Sx2 *(
                                                  (12.875*s2+0.625*sx2) + Sx2 *(
                                                                (59.0625*s2+0.9375*sx2) + Sx2 *(324.8*s2+3.28*sx2))))));
  
  p2 *= G4Exp(sx-s0);
  
  return p1-p2; 
}