G4ParticleHPFissionSpectrum.hh

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// P. Arce, June-2014 Conversion neutron_hp to particle_hp
//
#ifndef G4ParticleHPFissionSpectrum_h
#define G4ParticleHPFissionSpectrum_h 1

#include <fstream>
#include <CLHEP/Units/SystemOfUnits.h>

#include "globals.hh"
#include "G4ios.hh"
#include "Randomize.hh"
#include "G4Exp.hh"
#include "G4ParticleHPVector.hh"
#include "G4VParticleHPEDis.hh"

// we will need a List of these .... one per term.

class G4ParticleHPFissionSpectrum : public G4VParticleHPEDis
{
  public:
  G4ParticleHPFissionSpectrum()
  {
    expm1 = G4Exp(-1.);
  }
  ~G4ParticleHPFissionSpectrum()
  {
  }
  
  inline void Init(std::istream & aDataFile)
  {
    theFractionalProb.Init(aDataFile, CLHEP::eV);
    theThetaDist.Init(aDataFile, CLHEP::eV);
  }
  
  inline G4double GetFractionalProbability(G4double anEnergy)
  {
    return theFractionalProb.GetY(anEnergy);
  }
  
  inline G4double Sample(G4double anEnergy) 
  {
    G4double theta = theThetaDist.GetY(anEnergy);
    // here we need to sample Maxwells distribution, if 
    // need be.
    G4double result, cut;
    G4double range =50*CLHEP::MeV;
    G4double max = Maxwell((theta*CLHEP::eV)/2., theta);
    G4double value;
    G4int icounter=0;
    G4int icounter_max=1024;
    do
    {
      icounter++;
      if ( icounter > icounter_max ) {
     G4cout << "Loop-counter exceeded the threshold value at " << __LINE__ << "th line of " << __FILE__ << "." << G4endl;
         break;
      }
      result = range*G4UniformRand();
      value = Maxwell(result, theta);
      cut = G4UniformRand();
    }
    while(cut > value/max); // Loop checking, 11.05.2015, T. Koi
    return result;
  }
  
  private:
 
  // this is the function to sample from. 
  inline G4double Maxwell(G4double anEnergy, G4double theta)
  {
    G4double result = std::sqrt(anEnergy/CLHEP::eV)*G4Exp(-anEnergy/CLHEP::eV/theta);
    return result;
  }
  
  private:
  
  G4double expm1;
  
  G4ParticleHPVector theFractionalProb;
  
  G4ParticleHPVector theThetaDist;
  
};

#endif