G4NeutronHPSimpleEvapSpectrum.hh

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00027 // $Id$
00028 //
00029 #ifndef G4NeutronHPSimpleEvapSpectrum_h
00030 #define G4NeutronHPSimpleEvapSpectrum_h 1
00031 
00032 #include <fstream>
00033 #include <CLHEP/Units/SystemOfUnits.h>
00034 
00035 #include "globals.hh"
00036 #include "G4ios.hh"
00037 #include "Randomize.hh"
00038 #include "G4NeutronHPVector.hh"
00039 #include "G4VNeutronHPEDis.hh"
00040 
00041 // we will need a List of these .... one per term.
00042 
00043 class G4NeutronHPSimpleEvapSpectrum : public G4VNeutronHPEDis
00044 {
00045   public:
00046   G4NeutronHPSimpleEvapSpectrum()
00047   {
00048     expm1 = std::exp(-1.);
00049   }
00050   ~G4NeutronHPSimpleEvapSpectrum()
00051   {
00052   }
00053   
00054   inline void Init(std::ifstream & aDataFile)
00055   {
00056     theFractionalProb.Init(aDataFile, CLHEP::eV);
00057     theThetaDist.Init(aDataFile, CLHEP::eV);
00058   }
00059   
00060   inline G4double GetFractionalProbability(G4double anEnergy)
00061   {
00062     return theFractionalProb.GetY(anEnergy);
00063   }
00064   
00065   inline G4double Sample(G4double anEnergy) 
00066   {
00067     G4double theta = theThetaDist.GetY(anEnergy)*CLHEP::eV;
00068     G4double random, cut, max, result;
00069     max = 10.*theta;
00070     do
00071     {
00072       random = G4UniformRand();
00073       result = -theta*std::log(random); 
00074       cut = G4UniformRand();
00075     }
00076     while(cut>result/max); 
00077     return result;
00078   }
00079   
00080   private:
00081   
00082   inline G4double Evapo(G4double anEnergy, G4double theta)
00083   {
00084     G4double result = (anEnergy*CLHEP::eV)*std::exp(-anEnergy*CLHEP::eV/theta);
00085     return result;
00086   }
00087   
00088   private:
00089   
00090   G4double expm1;
00091   
00092   G4NeutronHPVector theFractionalProb;
00093   
00094   G4NeutronHPVector theThetaDist;
00095   
00096 };
00097 
00098 #endif

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