G4NeutronField.cc

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//
// -------------------------------------------------------------------
//      GEANT 4 class implementation file 
//
//      CERN, Geneva, Switzerland
//
//      File name:     G4NeutronField.cc
//
//      Author:        Alessandro Brunengo (Alessandro.Brunengo@ge.infn.it)
// 
//      Creation date: 5 June 2000
// -------------------------------------------------------------------

#include "G4NeutronField.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4VNuclearDensity.hh"
#include "G4FermiMomentum.hh"

G4NeutronField::G4NeutronField(G4V3DNucleus * aNucleus) : 
    G4VNuclearField(aNucleus), theDensity(theNucleus->GetNuclearDensity())
{ 
  theA = theNucleus->GetMassNumber();
  theZ = theNucleus->GetCharge();
  theFermi.Init(theA, theZ);
  theR = 2.*theNucleus->GetOuterRadius();
  G4double aR=0;
  while(aR<theR)
  {
    G4ThreeVector aPosition(0,0,aR);
    G4double density = GetDensity(aPosition);
    G4double fermiMom = GetFermiMomentum(density);
    theFermiMomBuffer.push_back(fermiMom);
    aR+=0.3*fermi;
  }
  {
  G4ThreeVector aPosition(0,0,theR);
  G4double density = GetDensity(aPosition);
  G4double fermiMom = GetFermiMomentum(density);
  theFermiMomBuffer.push_back(fermiMom);  
  }
  {
  G4ThreeVector aPosition(0,0,theR+0.001*fermi);
  theFermiMomBuffer.push_back(0);  
  }
  {
  G4ThreeVector aPosition(0,0,1.*m);
  theFermiMomBuffer.push_back(0);  
  }
}

G4NeutronField::~G4NeutronField()
{ }

G4double G4NeutronField::GetField(const G4ThreeVector & aPosition)
{
  G4double x = aPosition.mag();
  G4int index = static_cast<G4int>(x/(0.3*fermi) );
  if(index+2> static_cast<G4int>(theFermiMomBuffer.size())) return theFermiMomBuffer.back();
  G4double y1 = theFermiMomBuffer[index];
  G4double y2 = theFermiMomBuffer[index+1];
  G4double x1 = (0.3*fermi)*index;
  G4double x2 = (0.3*fermi)*(index+1);
  G4double fermiMom = y1 + (x-x1)*(y2-y1)/(x2-x1);
  return -1*(fermiMom*fermiMom)/(2*neutron_mass_c2);
}

G4double G4NeutronField::GetBarrier()
{
/*
 *   G4double A = theNucleus->GetMassNumber();
 *   G4double Z = theNucleus->GetCharge();
 * 
 *   return G4NucleiPropertiesTable::GetBindingEnergy(Z, A)/A;
 */
        return 0.;
}

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