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//
// neutron_hp -- source file
// J.P. Wellisch, Nov-1996
// A prototype of the low energy neutron transport model.
// P. Arce, June-2014 Conversion neutron_hp to particle_hp
//

#include "G4ParticleHPWattSpectrum.hh"

#include "G4SystemOfUnits.hh"

G4double G4ParticleHPWattSpectrum::Sample(G4double anEnergy)
{
  G4double a = theApar.GetY(anEnergy) * eV;
  G4double b = theBpar.GetY(anEnergy) / eV;
  G4double result = 0.;
  G4double random, cut, max;
  max = std::sinh(std::sqrt(b * 15. * a));

  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;
    }
    random = G4UniformRand();
    result = -a * G4Log(random);
    cut = G4UniformRand();
  } while (cut > std::sinh(std::sqrt(b * result)) / max);  // Loop checking, 11.05.2015, T. Koi
  return result;
}