G4PreCompoundFragment.cc

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// $Id: G4PreCompoundFragment.cc 108685 2018-02-27 07:58:38Z gcosmo $
//
// J. M. Quesada (August 2008).  
// Based  on previous work by V. Lara
//
// Modified:
// 06.09.2008 JMQ Also external choice has been added for:
//               - superimposed Coulomb barrier (if useSICB=true) 
// 20.08.2010 V.Ivanchenko cleanup
//

#include "G4PreCompoundFragment.hh"
#include "G4KalbachCrossSection.hh"
#include "G4ChatterjeeCrossSection.hh"
#include "Randomize.hh"

G4PreCompoundFragment::G4PreCompoundFragment(const G4ParticleDefinition* p,
               G4VCoulombBarrier* aCoulBarrier)
  : G4VPreCompoundFragment(p, aCoulBarrier)
{
  muu = probmax = 0.0;
  if(0 == theZ)      { index = 0; }
  else if(1 == theZ) { index = theA; }
  else               { index = theA + 1; }
}

G4PreCompoundFragment::~G4PreCompoundFragment()
{}

G4double G4PreCompoundFragment::
CalcEmissionProbability(const G4Fragment & aFragment)
{
  //G4cout << theCoulombBarrier << "  " << GetMaximalKineticEnergy() << G4endl;
  // If  theCoulombBarrier effect is included in the emission probabilities
  // Coulomb barrier is the lower limit of integration over kinetic energy

  theEmissionProbability = 0.0;

  if (theMaxKinEnergy <= theMinKinEnergy) { return 0.0; }    

  // compute power once
  if(0 < index) { 
    muu = G4KalbachCrossSection::ComputePowerParameter(theResA, index);
  }
  
  theEmissionProbability = 
    IntegrateEmissionProbability(theMinKinEnergy,theMaxKinEnergy,aFragment);
  /*
  G4cout << "## G4PreCompoundFragment::CalcEmisProb "
         << "Z= " << aFragment.GetZ_asInt() 
   << " A= " << aFragment.GetA_asInt()
   << " Elow= " << LowerLimit/MeV
   << " Eup= " << UpperLimit/MeV
   << " prob= " << theEmissionProbability
   << G4endl;
  */
  return theEmissionProbability;
}

G4double G4PreCompoundFragment::
IntegrateEmissionProbability(G4double low, G4double up,
           const G4Fragment & aFragment)
{  
  static const G4double den = 1.0/CLHEP::MeV;
  G4double del = (up - low);
  G4int nbins  = std::max(3,(G4int)(del*den));
  del /= (G4double)nbins;
  G4double e = low + 0.5*del;
  probmax = ProbabilityDistributionFunction(e, aFragment);
  //G4cout << "    0. e= " << e << "  y= " << probmax << G4endl;

  G4double sum = probmax;
  for (G4int i=1; i<nbins; ++i) {
    e += del;
    G4double y = ProbabilityDistributionFunction(e, aFragment); 
    probmax = std::max(probmax, y);
    sum += y;
    if(y < sum*0.01) { break; }
    //G4cout << "   " << i << ". e= " << e << "  y= " << y << " sum= " << sum << G4endl;
  }
  sum *= del;
  //G4cout << "Evap prob: " << sum << " probmax= " << probmax << G4endl;
  return sum;
}

G4double G4PreCompoundFragment::CrossSection(G4double ekin) const
{
  G4double res;
  if(OPTxs == 0) { 
    res = GetOpt0(ekin);

  } else if(OPTxs <= 2) { 
    res = G4ChatterjeeCrossSection::ComputeCrossSection(ekin, theCoulombBarrier, 
              theResA13, muu, 
              index, theZ, theResA); 

  } else { 
    res = G4KalbachCrossSection::ComputeCrossSection(ekin, theCoulombBarrier, 
                 theResA13, muu,
                 index, theZ, theA, theResA);
  }
  return res;
}  

// *********************** OPT=0 : Dostrovski's cross section  ***************
G4double G4PreCompoundFragment::GetOpt0(G4double ekin) const
{
  G4double r0 = theParameters->GetR0()*theResA13;
  // cross section is now given in mb (r0 is in mm) for the sake of consistency
  //with the rest of the options
  return 1.e+25*CLHEP::pi*r0*r0*theResA13*GetAlpha()*(1.+GetBeta()/ekin);
}

G4double G4PreCompoundFragment::SampleKineticEnergy(const G4Fragment& fragment) 
{
  G4double delta = theMaxKinEnergy - theMinKinEnergy;
  static const G4double toler = 1.25;
  probmax *= toler;
  G4double prob, T(0.0);
  CLHEP::HepRandomEngine* rndm = G4Random::getTheEngine();
  G4int i;
  for(i=0; i<100; ++i) {
    T = theMinKinEnergy + delta*rndm->flat();
    prob = ProbabilityDistributionFunction(T, fragment);
    /*
    if(prob > probmax) { 
      G4cout << "G4PreCompoundFragment WARNING: prob= " << prob 
       << " probmax= " << probmax << G4endl;
      G4cout << "i= " << i << " Z= " << theZ << " A= " << theA 
       << " resZ= " << theResZ << " resA= " << theResA << "\n"
       << " T= " << T << " Tmax= " << theMaxKinEnergy 
       << " Tmin= " << limit
       << G4endl;
      for(G4int i=0; i<N; ++i) { G4cout << " " << probability[i]; }
      G4cout << G4endl; 
    }
    */
    // Loop checking, 05-Aug-2015, Vladimir Ivanchenko
    if(probmax*rndm->flat() <= prob) { break; }
  }
  /*
  G4cout << "G4PreCompoundFragment: i= " << i << " Z= " << theZ << " A= " << theA 
   <<"  T(MeV)= " << T << " Emin(MeV)= " << theMinKinEnergy << " Emax= " 
   << theMaxKinEnergy << G4endl;
  */
  return T;
}