G4hBetheBlochModel.cc

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// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4hBetheBlochModel
//
// Author:        V.Ivanchenko (Vladimir.Ivanchenko@cern.ch)
// 
// Creation date: 20 July 2000
//
// Modifications: 
// 20/07/2000  V.Ivanchenko First implementation
// 03/10/2000  V.Ivanchenko clean up accoding to CodeWizard
//
// Class Description: 
//
// Bethe-Bloch ionisation model
//
// Class Description: End 
//
// -------------------------------------------------------------------
//
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#include "G4hBetheBlochModel.hh"

#include "globals.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4DynamicParticle.hh"
#include "G4ParticleDefinition.hh"
#include "G4Material.hh"

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G4hBetheBlochModel::G4hBetheBlochModel(const G4String& name)
  : G4VLowEnergyModel(name), 
    lowEnergyLimit(1.*MeV),
    highEnergyLimit(100.*GeV),
    twoln10(2.*std::log(10.)),
    bg2lim(0.0169), 
    taulim(8.4146e-3)
{;}

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G4hBetheBlochModel::~G4hBetheBlochModel() 
{;}

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G4double G4hBetheBlochModel::TheValue(const G4DynamicParticle* particle,
                                      const G4Material* material) 
{
  G4double energy = particle->GetKineticEnergy() ;
  G4double particleMass = particle->GetMass() ;

  G4double eloss  = BetheBlochFormula(material,energy,particleMass) ;

  return eloss ;
}

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G4double G4hBetheBlochModel::TheValue(const G4ParticleDefinition* aParticle,
                                      const G4Material* material,
                                      G4double kineticEnergy) 
{
  G4double particleMass = aParticle->GetPDGMass() ;
  G4double eloss  = BetheBlochFormula(material,kineticEnergy,particleMass) ;

  return eloss ;
}

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G4double G4hBetheBlochModel::HighEnergyLimit(
                             const G4ParticleDefinition* ,
                             const G4Material* ) const
{
  return highEnergyLimit ;
}

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G4double G4hBetheBlochModel::LowEnergyLimit(
                             const G4ParticleDefinition* aParticle,
                             const G4Material* material) const
{
  G4double taul = (material->GetIonisation()->GetTaul())*
                  (aParticle->GetPDGMass()) ;
  return taul ;
}

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G4double G4hBetheBlochModel::HighEnergyLimit(
                             const G4ParticleDefinition* ) const
{
  return highEnergyLimit ;
}

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G4double G4hBetheBlochModel::LowEnergyLimit(
                             const G4ParticleDefinition* ) const
{
  return lowEnergyLimit ;
}

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G4bool G4hBetheBlochModel::IsInCharge(const G4DynamicParticle* ,
                                      const G4Material* ) const
{
  return true ;
}

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G4bool G4hBetheBlochModel::IsInCharge(const G4ParticleDefinition* ,
                                      const G4Material* ) const
{
  return true ;
}

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G4double G4hBetheBlochModel::BetheBlochFormula(
                             const G4Material* material,
                                   G4double kineticEnergy,
                                   G4double particleMass) const
{
  // This member function is applied normally to proton/antiproton
  G4double ionloss ;

  G4double rateMass = electron_mass_c2/particleMass ;

  G4double taul = material->GetIonisation()->GetTaul() ;
  G4double tau  = kineticEnergy/particleMass ;    // tau is relative energy
  
  // It is not normal case for this function
  // for low energy parametrisation have to be applied
  if ( tau < taul ) tau = taul ; 
    
  // some local variables 
    
  G4double gamma,bg2,beta2,tmax,x,delta,sh ;
  G4double electronDensity = material->GetElectronDensity();
  G4double eexc  = material->GetIonisation()->GetMeanExcitationEnergy();
  G4double eexc2 = eexc*eexc ;
  G4double cden  = material->GetIonisation()->GetCdensity();
  G4double mden  = material->GetIonisation()->GetMdensity();
  G4double aden  = material->GetIonisation()->GetAdensity();
  G4double x0den = material->GetIonisation()->GetX0density();
  G4double x1den = material->GetIonisation()->GetX1density();
  G4double* shellCorrectionVector =
            material->GetIonisation()->GetShellCorrectionVector();
    
  gamma = tau + 1.0 ;
  bg2 = tau*(tau+2.0) ;
  beta2 = bg2/(gamma*gamma) ;
  tmax = 2.*electron_mass_c2*bg2/(1.+2.*gamma*rateMass+rateMass*rateMass) ;
        
  ionloss = std::log(2.0*electron_mass_c2*bg2*tmax/eexc2)-2.0*beta2 ;
    
  // density correction     
  x = std::log(bg2)/twoln10 ;
  if ( x < x0den ) {
    delta = 0.0 ;

  } else { 
    delta = twoln10*x - cden ;
    if ( x < x1den ) delta += aden*std::pow((x1den-x),mden) ;
  }
    
  // shell correction 
  sh = 0.0 ;      
  x  = 1.0 ;

  if ( bg2 > bg2lim ) {
    for (G4int k=0; k<=2; k++) {
        x *= bg2 ;
        sh += shellCorrectionVector[k]/x;
    }

  } else {
    for (G4int k=0; k<=2; k++) {
        x *= bg2lim ;
        sh += shellCorrectionVector[k]/x;
    }
    sh *= std::log(tau/taul)/std::log(taulim/taul) ;     
  }
    
  // now compute the total ionization loss
    
  ionloss -= delta + sh ;
  ionloss *= twopi_mc2_rcl2*electronDensity/beta2 ;

  if ( ionloss < 0.0) ionloss = 0.0 ;
  
  return ionloss;
}

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