G4E1SingleProbability1.cc

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// $Id$
//
//  Class G4E1SingleProbability1.cc
//
 
#include "G4E1SingleProbability1.hh"
#include "G4ConstantLevelDensityParameter.hh"
#include "Randomize.hh"
#include "G4Pow.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
 
// Constructors and operators
//
 
G4E1SingleProbability1::G4E1SingleProbability1()
{}
 
G4E1SingleProbability1::~G4E1SingleProbability1()
{}
 
// Calculate the emission probability
//
 
G4double G4E1SingleProbability1::EmissionProbDensity(const G4Fragment& frag, 
                             G4double exciteE)
{
 
  // Calculate the probability density here
 
  // From nuclear fragment properties and the excitation energy, calculate
  // the probability density for photon evaporation from U to U - exciteE
  // (U = nucleus excitation energy, exciteE = total evaporated photon
  // energy).
  // fragment = nuclear fragment BEFORE de-excitation
 
  G4double theProb = 0.0;
 
  G4int Afrag = frag.GetA_asInt();
  G4int Zfrag = frag.GetZ_asInt();
  G4double Uexcite = frag.GetExcitationEnergy();
 
  if( (Uexcite-exciteE) < 0.0 || exciteE < 0 || Uexcite <= 0) return theProb;
 
  // Need a level density parameter.
  // For now, just use the constant approximation (not reliable near magic
  // nuclei).
 
  G4ConstantLevelDensityParameter a;
  G4double aLevelDensityParam = a.LevelDensityParameter(Afrag,Zfrag,Uexcite);
 
  G4double levelDensBef = std::exp(2.0*std::sqrt(aLevelDensityParam*Uexcite));
  G4double levelDensAft = std::exp(2.0*std::sqrt(aLevelDensityParam*(Uexcite-exciteE)));
 
  // Now form the probability density
 
  // Define constants for the photoabsorption cross-section (the reverse
  // process of our de-excitation)
 
  G4double sigma0 = 2.5 * Afrag * millibarn;  // millibarns
 
  G4double Egdp = (40.3 / G4Pow::GetInstance()->powZ(Afrag,0.2) )*MeV;
  G4double GammaR = 0.30 * Egdp;
 
  const G4double normC = 1.0 / ((pi * hbarc)*(pi * hbarc));
 
  // CD
  //cout<<"  PROB TESTS "<<G4endl;
  //cout<<" hbarc = "<<hbarc<<G4endl;
  //cout<<" pi = "<<pi<<G4endl;
  //cout<<" Uexcite, exciteE = "<<Uexcite<<"  "<<exciteE<<G4endl;
  //cout<<" Uexcite, exciteE = "<<Uexcite*MeV<<"  "<<exciteE*MeV<<G4endl;
  //cout<<" lev density param = "<<aLevelDensityParam<<G4endl;
  //cout<<" level densities = "<<levelDensBef<<"  "<<levelDensAft<<G4endl;
  //cout<<" sigma0 = "<<sigma0<<G4endl;
  //cout<<" Egdp, GammaR = "<<Egdp<<"  "<<GammaR<<G4endl;
  //cout<<" normC = "<<normC<<G4endl;
 
  G4double numerator = sigma0 * exciteE*exciteE * GammaR*GammaR;
  G4double denominator = (exciteE*exciteE - Egdp*Egdp)*
           (exciteE*exciteE - Egdp*Egdp) + GammaR*GammaR*exciteE*exciteE;
 
  G4double sigmaAbs = numerator/denominator; 
 
  theProb = normC * sigmaAbs * exciteE*exciteE *
            levelDensAft/levelDensBef;
 
  // CD
  //cout<<" sigmaAbs = "<<sigmaAbs<<G4endl;
  //cout<<" Probability = "<<theProb<<G4endl;
 
  return theProb;
 
}
 
G4double G4E1SingleProbability1::EmissionProbability(const G4Fragment& frag, 
                             G4double exciteE)
{
 
  // From nuclear fragment properties and the excitation energy, calculate
  // the probability for photon evaporation down to the level
  // Uexcite-exciteE.
  // fragment = nuclear fragment BEFORE de-excitation
 
  G4double theProb = 0.0;
 
  G4double ScaleFactor = 1.0;     // playing with scale factors
 
  const G4double Uexcite = frag.GetExcitationEnergy();
  G4double Uafter = Uexcite - exciteE;
 
  G4double normC = 3.0;
 
  const G4double upperLim = Uexcite;
  const G4double lowerLim = Uafter;
  const G4int numIters = 25;
 
  // Need to integrate EmissionProbDensity from lowerLim to upperLim 
  // and multiply by normC
 
  G4double integ = normC *
           EmissionIntegration(frag,exciteE,lowerLim,upperLim,numIters);
 
  if(integ > 0.0) theProb = integ;
 
  return theProb * ScaleFactor;
 
}
 
G4double G4E1SingleProbability1::EmissionIntegration(const G4Fragment& frag, 
                             G4double ,
                             G4double lowLim, G4double upLim,
                             G4int numIters)
 
{
 
  // Simple Gaussian quadrature integration
 
  G4double x;
  const G4double root3 = 1.0/std::sqrt(3.0);
 
  G4double Step = (upLim-lowLim)/(2.0*numIters);
  G4double Delta = Step*root3;
 
  G4double mean = 0.0;
 
  G4double theInt = 0.0;
 
  for(G4int i = 0; i < numIters; i++) {
 
    x = (2*i + 1)/Step;
    G4double E1ProbDensityA = EmissionProbDensity(frag,x+Delta);
    G4double E1ProbDensityB = EmissionProbDensity(frag,x-Delta);
 
    mean += E1ProbDensityA + E1ProbDensityB;
 
  }
 
  if(mean*Step > 0.0) theInt = mean*Step;
 
  return theInt;
 
}