include/Geant4/G4ParticleHPFissionSpectrum.hh

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0025 //
0026 //
0027 // P. Arce, June-2014 Conversion neutron_hp to particle_hp
0028 //
0029 #ifndef G4ParticleHPFissionSpectrum_h
0030 #define G4ParticleHPFissionSpectrum_h 1
0031
0032 #include "G4Exp.hh"
0033 #include "G4ParticleHPVector.hh"
0034 #include "G4VParticleHPEDis.hh"
0035 #include "G4ios.hh"
0036 #include "Randomize.hh"
0037 #include "globals.hh"
0038
0039 #include <CLHEP/Units/SystemOfUnits.h>
0040
0041 #include <fstream>
0042
0043 // we will need a List of these .... one per term.
0044
0045 class G4ParticleHPFissionSpectrum : public G4VParticleHPEDis
0046 {
0047   public:
0048     G4ParticleHPFissionSpectrum() { expm1 = G4Exp(-1.); }
0049     ~G4ParticleHPFissionSpectrum() override = default;
0050
0051     inline void Init(std::istream& aDataFile) override
0052     {
0053       theFractionalProb.Init(aDataFile, CLHEP::eV);
0054       theThetaDist.Init(aDataFile, CLHEP::eV);
0055     }
0056
0057     inline G4double GetFractionalProbability(G4double anEnergy) override
0058     {
0059       return theFractionalProb.GetY(anEnergy);
0060     }
0061
0062     inline G4double Sample(G4double anEnergy) override
0063     {
0064       G4double theta = theThetaDist.GetY(anEnergy);
0065       // here we need to sample Maxwells distribution, if
0066       // need be.
0067       G4double result = 0., cut;
0068       G4double range = 50 * CLHEP::MeV;
0069       G4double max = Maxwell((theta * CLHEP::eV) / 2., theta);
0070       G4double value;
0071       G4int icounter = 0;
0072       G4int icounter_max = 1024;
0073       do {
0074         icounter++;
0075         if (icounter > icounter_max) {
0076           G4cout << "Loop-counter exceeded the threshold value at " << __LINE__ << "th line of "
0077                  << __FILE__ << "." << G4endl;
0078           break;
0079         }
0080         result = range * G4UniformRand();
0081         value = Maxwell(result, theta);
0082         cut = G4UniformRand();
0083       } while (cut > value / max);  // Loop checking, 11.05.2015, T. Koi
0084       return result;
0085     }
0086
0087   private:
0088     // this is the function to sample from.
0089     inline G4double Maxwell(G4double anEnergy, G4double theta)
0090     {
0091       G4double result = std::sqrt(anEnergy / CLHEP::eV) * G4Exp(-anEnergy / CLHEP::eV / theta);
0092       return result;
0093     }
0094
0095   private:
0096     G4double expm1;
0097
0098     G4ParticleHPVector theFractionalProb;
0099
0100     G4ParticleHPVector theThetaDist;
0101 };
0102
0103 #endif