G4IonCoulombScatteringModel.cc

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//
//      G4IonCoulombScatteringModel.cc
// -------------------------------------------------------------------
//
// GEANT4 Class header file
//
// File name:    G4IonCoulombScatteringModel
//
// Author:      Cristina Consolandi
//
// Creation date: 05.10.2010 from G4eCoulombScatteringModel 
//                               & G4CoulombScatteringModel
//
// Class Description:
//      Single Scattering Model for
//      for protons, alpha and heavy Ions
//
// Reference:
//      M.J. Boschini et al. "Nuclear and Non-Ionizing Energy-Loss 
//      for Coulomb ScatteredParticles from Low Energy up to Relativistic 
//      Regime in Space Radiation Environment"
//      Accepted for publication in the Proceedings of  the  ICATPP Conference
//      on Cosmic Rays for Particle and Astroparticle Physics, Villa  Olmo, 7-8
//      October,  2010, to be published by World Scientific (Singapore).
//
//      Available for downloading at:
//      http://arxiv.org/abs/1011.4822
//
// -------------------------------------------------------------------
//
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#include "G4IonCoulombScatteringModel.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"
#include "G4ParticleChangeForGamma.hh"
#include "G4Proton.hh"
#include "G4ProductionCutsTable.hh"
#include "G4NucleiProperties.hh"
#include "G4ParticleTable.hh"
#include "G4IonTable.hh"

#include "G4UnitsTable.hh"

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using namespace std;

G4IonCoulombScatteringModel::G4IonCoulombScatteringModel(const G4String& nam)
  : G4VEmModel(nam),
    cosThetaMin(1.0),
    isInitialised(false)
{
  fNistManager = G4NistManager::Instance();
  theIonTable  = G4ParticleTable::GetParticleTable()->GetIonTable();
  theProton    = G4Proton::Proton();

  pCuts=0;
  currentMaterial = 0;
  currentElement  = 0;
  currentCouple = 0;

  lowEnergyLimit  = 100*eV;
  recoilThreshold = 0.*eV;
  heavycorr =0;
  particle = 0;
  mass=0;
  currentMaterialIndex = -1;

  ioncross = new G4IonCoulombCrossSection(); 
}


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G4IonCoulombScatteringModel::~G4IonCoulombScatteringModel()
{ 
  delete  ioncross;
}

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void G4IonCoulombScatteringModel::Initialise(const G4ParticleDefinition* p,
                                             const G4DataVector& cuts)
{
  SetupParticle(p);
  currentCouple = 0;
  currentMaterialIndex = -1;
  ioncross->Initialise(p,cosThetaMin);
 
  pCuts = &cuts;
  //  G4ProductionCutsTable::GetProductionCutsTable()->GetEnergyCutsVector(3);
  if(!isInitialised) {
    isInitialised = true;
    fParticleChange = GetParticleChangeForGamma();
  }
}

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G4double G4IonCoulombScatteringModel::ComputeCrossSectionPerAtom(
                                const G4ParticleDefinition* p,
                                G4double kinEnergy, 
                                G4double Z, 
                                G4double, 
                                G4double cutEnergy,
                                G4double)
{
  SetupParticle(p);
 
  G4double cross = 0.0;
  if(kinEnergy > lowEnergyLimit) {

    DefineMaterial(CurrentCouple());

    G4int iz = G4int(Z);

    //from lab to pCM & mu_rel of effective particle
    G4double tmass = proton_mass_c2;
    if(1 < iz) {
      tmass = fNistManager->GetAtomicMassAmu(iz)*amu_c2;
    }
    ioncross->SetupKinematic(kinEnergy, cutEnergy, tmass);

    ioncross->SetupTarget(Z, kinEnergy, heavycorr);
  
    cross = ioncross->NuclearCrossSection();
  }
  //cout<< "..........cross "<<G4BestUnit(cross,"Surface") <<endl;
  return cross;
}

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void G4IonCoulombScatteringModel::SampleSecondaries(
                               std::vector<G4DynamicParticle*>* fvect,
                               const G4MaterialCutsCouple* couple,
                               const G4DynamicParticle* dp,
                               G4double cutEnergy, 
                               G4double)
{
  G4double kinEnergy = dp->GetKineticEnergy();

  if(kinEnergy <= lowEnergyLimit) return;
        
  DefineMaterial(couple);

  SetupParticle(dp->GetDefinition());

  // Choose nucleus
  currentElement = SelectRandomAtom(couple,particle,
                                    kinEnergy,cutEnergy,kinEnergy);

  G4double Z  = currentElement->GetZ();
  G4int iz = G4int(Z);
  G4int ia = SelectIsotopeNumber(currentElement);
  G4double mass2 = G4NucleiProperties::GetNuclearMass(ia, iz);

  ioncross->SetupKinematic(kinEnergy, cutEnergy, mass2);

  ioncross->SetupTarget(Z, kinEnergy, heavycorr);
    
  //scattering angle, z1 == (1-cost)
  G4double z1 = ioncross->SampleCosineTheta(); 
  if(z1 > 2.0)      { z1 = 2.0; }
  else if(z1 < 0.0) { z1 = 0.0; }

  G4double cost = 1.0 - z1;
  G4double sint = sqrt(z1*(1.0 + cost));
  G4double phi  = twopi * G4UniformRand();

  G4LorentzVector v0 = dp->Get4Momentum();

  // kinematics in the Lab system
  G4double etot = v0.e();
  G4double ptot = v0.mag();
  
  //CM particle 1
  G4double bet  = ptot/(etot + mass2);
  G4double gam  = 1.0/sqrt((1.0 - bet)*(1.0 + bet));

  //CM  
  G4double momCM = gam*(ptot - bet*etot); 
  G4double eCM   = gam*(etot - bet*ptot); 
  //energy & momentum after scattering of incident particle
  G4double pxCM = momCM*sint*cos(phi);
  G4double pyCM = momCM*sint*sin(phi);
  G4double pzCM = momCM*cost;

  //CM--->Lab
  G4LorentzVector v1(pxCM , pyCM, gam*(pzCM + bet*eCM), gam*(eCM + bet*pzCM));

  G4ThreeVector dir = dp->GetMomentumDirection(); 
  G4ThreeVector newDirection = v1.vect().unit();
  newDirection.rotateUz(dir);   
  
  fParticleChange->ProposeMomentumDirection(newDirection);   
  
  // recoil
  v0 -= v1; 
  G4double trec = v0.e() - mass2;
  G4double edep = 0.0;

  G4double tcut = recoilThreshold;
  if(pCuts) { 
    tcut= std::max(tcut,(*pCuts)[currentMaterialIndex]); 
    //G4cout<<" tcut eV "<<tcut/eV<<endl;
  }
 
  if(trec > tcut) {
    G4ParticleDefinition* ion = theIonTable->GetIon(iz, ia, 0);
    G4DynamicParticle* newdp  = new G4DynamicParticle(ion, v0);
    fvect->push_back(newdp);
  } else if(trec > 0.0) {
    edep = trec;
    fParticleChange->ProposeNonIonizingEnergyDeposit(edep);
  }

  // finelize primary energy and energy balance
  G4double finalT = v1.e() - mass;
  if(finalT <= lowEnergyLimit) { 
    edep += finalT;
    finalT = 0.0;
    if(edep < 0.0) { edep = 0.0; }
  } 
  fParticleChange->SetProposedKineticEnergy(finalT);
  fParticleChange->ProposeLocalEnergyDeposit(edep);
}

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