G4RToEConvForPositron.cc

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// $Id$
//
//
// --------------------------------------------------------------
//      GEANT 4 class implementation file/  History:
//    5 Oct. 2002, H.Kuirashige : Structure created based on object model
// --------------------------------------------------------------
 
#include "G4RToEConvForPositron.hh"
#include "G4ParticleDefinition.hh"
#include "G4ParticleTable.hh"
#include "G4Material.hh"
#include "G4PhysicsLogVector.hh"
 
#include "G4ios.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
 
G4RToEConvForPositron::G4RToEConvForPositron() : G4VRangeToEnergyConverter()
{    
  theParticle =  G4ParticleTable::GetParticleTable()->FindParticle("e+");
  if (theParticle ==0) {
#ifdef G4VERBOSE
    if (GetVerboseLevel()>0) {
      G4cout << " G4RToEConvForPositron::G4RToEConvForPositron() ";
      G4cout << " Positron is not defined !!" << G4endl;
    }
#endif
  } 
}
 
G4RToEConvForPositron::~G4RToEConvForPositron()
{ 
}
 
 
 
 
// **********************************************************************
// ************************* ComputeLoss ********************************
// **********************************************************************
G4double G4RToEConvForPositron::ComputeLoss(G4double AtomicNumber,
                        G4double KineticEnergy) const
{
  static G4double Z;  
  static G4double taul, ionpot, ionpotlog;
  const  G4double cbr1=0.02, cbr2=-5.7e-5, cbr3=1., cbr4=0.072;
  const  G4double Tlow=10.*keV, Thigh=1.*GeV;
  static G4double bremfactor = 0.1 ;
 
  G4double Mass = theParticle->GetPDGMass();       
  //  calculate dE/dx for electrons
  if( std::fabs(AtomicNumber-Z)>0.1 ) {
    Z = AtomicNumber;
    taul = Tlow/Mass;
    ionpot = 1.6e-5*MeV*std::exp(0.9*std::log(Z))/Mass;
    ionpotlog = std::log(ionpot);
  } 
 
  G4double tau = KineticEnergy/Mass;
  G4double dEdx;
 
 if(tau<taul)
  {
    G4double t1 = taul+1.;
    G4double t2 = taul+2.;
    G4double tsq = taul*taul;
    G4double beta2 = taul*t2/(t1*t1);
    G4double     f = 2.*std::log(taul)
                     -(6.*taul+1.5*tsq-taul*(1.-tsq/3.)/t2-tsq*(0.5-tsq/12.)/
                       (t2*t2))/(t1*t1);
    dEdx = (std::log(2.*taul+4.)-2.*ionpotlog+f)/beta2;
    dEdx = twopi_mc2_rcl2*Z*dEdx;
    G4double clow = dEdx*std::sqrt(taul);
    dEdx = clow/std::sqrt(KineticEnergy/Mass);
 
  } else {
   G4double t1 = tau+1.;
    G4double t2 = tau+2.;
    G4double tsq = tau*tau;
    G4double beta2 = tau*t2/(t1*t1);
    G4double f = 2.*std::log(tau)
                 - (6.*tau+1.5*tsq-tau*(1.-tsq/3.)/t2-tsq*(0.5-tsq/12.)/
                     (t2*t2))/(t1*t1);
    dEdx = (std::log(2.*tau+4.)-2.*ionpotlog+f)/beta2;
    dEdx = twopi_mc2_rcl2*Z*dEdx;
 
    // loss from bremsstrahlung follows
    G4double cbrem = (cbr1+cbr2*Z)
                       *(cbr3+cbr4*std::log(KineticEnergy/Thigh));
    cbrem = Z*(Z+1.)*cbrem*tau/beta2;
    cbrem *= bremfactor ;
    dEdx += twopi_mc2_rcl2*cbrem;
  }
  return dEdx;
}