G4IonYangFluctuationModel.cc

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//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4IonYangFluctuationModel
//
// Author:        V.Ivanchenko (Vladimir.Ivanchenko@cern.ch)
// 
// Creation date: 18 August 2000
//
// Modifications: 
// 18/08/2000  V.Ivanchenko First implementation
// 04/09/2000  V.Ivanchenko Rename fluctuations            
// 03/10/2000  V.Ivanchenko CodeWizard clean up
// 10/05/2001  V.Ivanchenko Clean up againist Linux compilation with -Wall
//
// -------------------------------------------------------------------
// Class Description: 
//
// The aproximation of additional ion energy loss fluctuations 
// Q.Yang et al., NIM B61(1991)149-155.
//
// Class Description: End 
//
// -------------------------------------------------------------------
//
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#include "G4IonYangFluctuationModel.hh"

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

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G4IonYangFluctuationModel::G4IonYangFluctuationModel(const G4String& name)
  : G4VLowEnergyModel(name)
{;}

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G4IonYangFluctuationModel::~G4IonYangFluctuationModel() 
{;}

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G4double G4IonYangFluctuationModel::TheValue(const G4DynamicParticle* particle,
                                             const G4Material* material) 
{
  G4double energy = particle->GetKineticEnergy() ;
  G4double mass = particle->GetMass() ;
  G4double charge = (particle->GetCharge())/eplus ;

  G4double q = YangFluctuationModel(material,energy,mass,charge) ;

  return q ;
}

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G4double G4IonYangFluctuationModel::TheValue(const G4ParticleDefinition* aParticle,
                                             const G4Material* material,
                                             G4double kineticEnergy) 
{
  G4double mass = aParticle->GetPDGMass() ;
  G4double charge = (aParticle->GetPDGCharge())/eplus ;

  G4double q = YangFluctuationModel(material,kineticEnergy,mass,charge);

  return q ;
}

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G4double G4IonYangFluctuationModel::HighEnergyLimit(const G4ParticleDefinition*,
                                                    const G4Material*) const
{
  return 1.0*TeV ;
}

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G4double G4IonYangFluctuationModel::LowEnergyLimit(const G4ParticleDefinition* ,
                                                   const G4Material* ) const
{
  return 0.0 ;
}

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G4double G4IonYangFluctuationModel::HighEnergyLimit(const G4ParticleDefinition* ) const
{
  return 1.0*TeV ;
}

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G4double G4IonYangFluctuationModel::LowEnergyLimit(
                              const G4ParticleDefinition* ) const
{
  return 0.0 ;
}

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G4bool G4IonYangFluctuationModel::IsInCharge(const G4DynamicParticle*,
                                             const G4Material* ) const
{
  return true ;
}

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G4bool G4IonYangFluctuationModel::IsInCharge(const G4ParticleDefinition* ,
                                             const G4Material* ) const
{
  return true ;
}

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G4double G4IonYangFluctuationModel::YangFluctuationModel(const G4Material* material,
                                                         G4double kineticEnergy,
                                                         G4double particleMass,
                                                         G4double charge) const
{
  // The aproximation of energy loss fluctuations 
  // Q.Yang et al., NIM B61(1991)149-155.

  // Reduced energy in MeV/AMU
  G4double energy = kineticEnergy *amu_c2/(particleMass*MeV) ;

  G4int i = 0 ;
  G4double factor = 1.0 ;

  // The index of set of parameters i = 0 for protons(hadrons) in gases
  //                                    1 for protons(hadrons) in solids
  //                                    2 for ions in atomic gases
  //                                    3 for ions in molecular gases
  //                                    4 for ions in solids
  static const G4double b[5][4] = {
  {0.1014,  0.3700,  0.9642,  3.987},
  {0.1955,  0.6941,  2.522,   1.040},
  {0.05058, 0.08975, 0.1419, 10.80},
  {0.05009, 0.08660, 0.2751,  3.787},
  {0.01273, 0.03458, 0.3951,  3.812}
  } ;

  // protons (hadrons) 
  if(1.5 > charge) {
    if( kStateGas != material->GetState() ) i = 1 ;

  // ions
  } else {
    G4double zeff = (material->GetElectronDensity())/
                    (material->GetTotNbOfAtomsPerVolume()) ;
    factor = charge * std::pow(charge/zeff, 0.3333) ;

    if( kStateGas == material->GetState() ) {
      energy /= (charge * std::sqrt(charge)) ;      

      if(1 == (material->GetNumberOfElements())) {
        i = 2 ;
      } else {
        i = 3 ;
      }

    } else {
      energy /= (charge * std::sqrt(charge*zeff)) ;      
      i = 4 ;
    }
  }

  G4double x = b[i][2] * (1.0 - std::exp( - energy * b[i][3] )) ;

  G4double q = factor * x * b[i][0] / 
             ((energy - b[i][1])*(energy - b[i][1]) + x*x) ;

  return q ;    
}