G4eSingleCoulombScatteringModel.cc

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//
//      G4eSingleCoulombScatteringModel.cc
// -------------------------------------------------------------------
//
// GEANT4 Class header file
//
// File name:    G4eSingleCoulombScatteringModel
//
// Author:      Cristina Consolandi
//
// Creation date: 20.10.2012  
//                           
//      Class Description:
//      Single Scattering model for electron-nuclei interaction.
//      Suitable for high energy electrons and low scattering angles.
//
//
// Reference:
//      M.J. Boschini et al. "Non Ionizing Energy Loss induced by Electrons 
//      in the Space Environment" Proc. of the 13th International Conference 
//      on Particle Physics and Advanced Technology 
//
//      (13th ICPPAT, Como 3-7/10/2011), World Scientific (Singapore).
//      Available at: http://arxiv.org/abs/1111.4042v4
//
//
// -------------------------------------------------------------------
//
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#include "G4eSingleCoulombScatteringModel.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"
#include "G4ParticleChangeForGamma.hh"
#include "G4Proton.hh"
#include "G4ProductionCutsTable.hh"
#include "G4NucleiProperties.hh"
#include "G4NistManager.hh"
#include "G4ParticleTable.hh"
#include "G4IonTable.hh"

#include "G4UnitsTable.hh"


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using namespace std;

G4eSingleCoulombScatteringModel::G4eSingleCoulombScatteringModel(const G4String& nam)
  : G4VEmModel(nam),
    cosThetaMin(1.0),
    isInitialised(false)
{
  fNistManager = G4NistManager::Instance();
  theIonTable = G4ParticleTable::GetParticleTable()->GetIonTable();
  fParticleChange = 0;

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

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

  Mottcross = new G4ScreeningMottCrossSection(); 
}

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G4eSingleCoulombScatteringModel::~G4eSingleCoulombScatteringModel()
{ 
  delete  Mottcross;
}

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void G4eSingleCoulombScatteringModel::Initialise(const G4ParticleDefinition* p,
                                                 const G4DataVector&  cuts)
{
  SetupParticle(p);
  currentCouple = 0;
  currentMaterialIndex = -1;
  //cosThetaMin = cos(PolarAngleLimit());
  Mottcross->Initialise(p,cosThetaMin);
 
  pCuts = &cuts; 
  //G4ProductionCutsTable::GetProductionCutsTable()->GetEnergyCutsVector(3);


  if(!isInitialised) {
    isInitialised = true;
    fParticleChange = GetParticleChangeForGamma();
  }
}

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G4double G4eSingleCoulombScatteringModel::ComputeCrossSectionPerAtom(
                                const G4ParticleDefinition* p,
                                G4double kinEnergy, 
                                G4double Z, 
                                G4double , 
                                G4double, 
                                G4double )
{
  SetupParticle(p);
 
  G4double cross =0.0;
  if(kinEnergy < lowEnergyLimit) return cross;

  DefineMaterial(CurrentCouple());

  //Total Cross section
  Mottcross->SetupKinematic(kinEnergy, Z);
  cross = Mottcross->NuclearCrossSection();

  //cout<< "....cross "<<G4BestUnit(cross,"Surface") << " cm2 "<< cross/cm2 <<endl;
  return cross;
}

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void G4eSingleCoulombScatteringModel::SampleSecondaries(
                               std::vector<G4DynamicParticle*>* fvect,
                               const G4MaterialCutsCouple* couple,
                               const G4DynamicParticle* dp,
                               G4double cutEnergy, 
                               G4double)
{
  G4double kinEnergy = dp->GetKineticEnergy();
  //cout<<"--- kinEnergy "<<kinEnergy<<endl;

  if(kinEnergy < lowEnergyLimit) return;
        
  DefineMaterial(couple);
  SetupParticle(dp->GetDefinition());

  // Choose nucleus
  //last two :cutEnergy= min e kinEnergy=max
  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);

  //G4cout<<"..Z: "<<Z<<" ..iz: "<<iz<<" ..ia: "<<ia<<" ..mass2: "<<mass2<<G4endl;

  Mottcross->SetupKinematic(kinEnergy, Z);

  G4double z1 = Mottcross->GetScatteringAngle();
  G4double sint = sin(z1);
  G4double cost = sqrt(1.0 - sint*sint);
  G4double phi  = twopi* G4UniformRand();

  // kinematics in the Lab system
  G4double ptot = dp->GetTotalMomentum();
  G4double e1   = dp->GetTotalEnergy();
  // Lab. system kinematics along projectile direction
  G4LorentzVector v0 = G4LorentzVector(0, 0, ptot, e1);
  G4double bet  = ptot/(v0.e() + mass2);
  G4double gam  = 1.0/sqrt((1.0 - bet)*(1.0 + bet));

  //CM Projectile       
  G4double momCM = gam*(ptot - bet*e1); 
  G4double eCM   = gam*(e1 - 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));
  
  // Rotate to global system
  G4ThreeVector dir = dp->GetMomentumDirection(); 
  G4ThreeVector newDirection = v1.vect().unit();
  newDirection.rotateUz(dir);
  
  fParticleChange->ProposeMomentumDirection(newDirection);   

  // recoil
  v0 -= v1;
  G4double trec = v0.e();
  G4double edep = 0.0;

  G4double tcut = recoilThreshold;

  //G4cout<<" Energy Transfered: "<<trec/eV<<G4endl;
  
  if(pCuts) { 
    tcut= std::max(tcut,(*pCuts)[currentMaterialIndex]); 
  }

  if(trec > tcut) {
    G4ParticleDefinition* ion = theIonTable->GetIon(iz, ia, 0);
    newDirection = v0.vect().unit();
    newDirection.rotateUz(dir);
    G4DynamicParticle* newdp  = new G4DynamicParticle(ion, newDirection, trec);
    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;
  //G4cout<<"Final Energy: "<<finalT/eV<<G4endl;
  if(finalT <= lowEnergyLimit) { 
    edep += finalT;  
    finalT = 0.0;
  } 
  edep = std::max(edep, 0.0);
  fParticleChange->SetProposedKineticEnergy(finalT);
  fParticleChange->ProposeLocalEnergyDeposit(edep);

}

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