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// $Id: G4ionGasIonisation.cc,v 1.4 2008/01/14 11:59:45 vnivanch Exp $
// GEANT4 tag $Name: geant4-09-01-patch-02 $
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4ionGasIonisation
//
// Author:        Vladimir Ivanchenko
//
// Creation date: 23.07.2007
//
// Modifications:
//
//
// -------------------------------------------------------------------
//
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#include "G4ionGasIonisation.hh"
#include "G4Electron.hh"
#include "G4Proton.hh"
#include "G4GenericIon.hh"

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using namespace std;

G4ionGasIonisation::G4ionGasIonisation(const G4String& name)
  : G4ionIonisation(name),
    currParticle(0),
    baseParticle(0),
    initialised(false)
{
  atomXS = CLHEP::pi*CLHEP::Bohr_radius*CLHEP::Bohr_radius;
  verboseLevel = 1;
}

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G4ionGasIonisation::~G4ionGasIonisation()
{}

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void G4ionGasIonisation::InitialiseEnergyLossProcess(
		      const G4ParticleDefinition* part,
		      const G4ParticleDefinition* bpart)
{
  G4ionIonisation::InitialiseEnergyLossProcess(part, bpart);
  if(initialised) return;

  currParticle = part;

  if(part == bpart || part == G4GenericIon::GenericIon()) baseParticle = 0;
  else if(bpart == 0) baseParticle = G4GenericIon::GenericIon();
  else                baseParticle = bpart;

  if(baseParticle) basePartMass = baseParticle->GetPDGMass();
  else             basePartMass = currParticle->GetPDGMass();
  
  initialised = true;
}

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void G4ionGasIonisation::PrintInfo()
{
  G4ionIonisation::PrintInfo();
  G4cout << "      Version of ion process with simulation discrete ion/media change exchange."
	 << G4endl;	 
}

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void G4ionGasIonisation::InitialiseMassCharge(const G4Track& track)
{
  // First step of an ion
  if(track.GetCurrentStepNumber() == 1) {
    currParticle = track.GetDefinition();
    ionZ = G4int(currParticle->GetPDGCharge()/eplus + 0.5);
    currentIonZ = G4int(track.GetDynamicParticle()->GetCharge()/eplus + 0.5);
    currMassRatio = basePartMass/currParticle->GetPDGMass();
  }
  // any step 
  G4double q = eplus*currentIonZ;
  SetDynamicMassCharge(currMassRatio, q*q);
  preStepKinEnergy = track.GetKineticEnergy();
}

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void G4ionGasIonisation::CorrectionsAlongStep(const G4MaterialCutsCouple* couple,
					      const G4DynamicParticle* dp,
					      G4double& eloss,
					      G4double& s)
{
  const G4ParticleDefinition* part = dp->GetDefinition();
  const G4Material* mat = couple->GetMaterial();
  // add corrections
  if(eloss < preStepKinEnergy) {

    // use Bethe-Bloch with corrections
    if(preStepKinEnergy*currMassRatio > BetheBlochEnergyThreshold())
      eloss += s*corr->HighOrderCorrections(part,mat,preStepKinEnergy);

    // effective number of collisions
    G4double x = mat->GetElectronDensity()*s*atomXS;
    // equilibrium charge
    G4double q = fParticleChange.GetProposedCharge(); 
  
    // sample charge change during the step
    fParticleChange.SetProposedCharge(SampleChargeAfterStep(q, x));
  }

  // use nuclear stopping 
  if(NuclearStoppingFlag()) {
    G4double nloss = s*corr->NuclearDEDX(part,mat,preStepKinEnergy - eloss*0.5);
    eloss += nloss;
    fParticleChange.ProposeNonIonizingEnergyDeposit(nloss);
  }
}

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G4double G4ionGasIonisation::SampleChargeAfterStep(G4double qeff, G4double xeff)
{
  // qeff - equilibrium charge
  // xeff - effective number of collisions
  // q    - current charge
  G4double q = eplus*currentIonZ;
  if(verboseLevel > 1) G4cout << "G4ionGasIonisation: Q1= " << currentIonZ
			      << " Qeff= " << qeff/eplus << "  Neff= " << xeff
			      << G4endl;
  return q;
}

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