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 "G4SystemOfUnits.hh"
#include "Randomize.hh"
#include "G4ParticleChangeForGamma.hh"
#include "G4Proton.hh"
#include "G4ProductionCutsTable.hh"
#include "G4NucleiProperties.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();
        theParticleTable = G4ParticleTable::GetParticleTable();
        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&  )
{
        SetupParticle(p);
        currentCouple = 0;
        currentMaterialIndex = -1;
        cosThetaMin = cos(PolarAngleLimit());
        Mottcross->Initialise(p,cosThetaMin);
 
        pCuts = 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
        currentElement = SelectRandomAtom(couple,particle,
                                    kinEnergy,cutEnergy,kinEnergy);//last two :cutEnergy= min e kinEnergy=max

        G4double Z  = currentElement->GetZ();
        G4int iz    = G4int(Z);
        G4int ia = SelectIsotopeNumber(currentElement);

        //cout<<"Element "<<currentElement->GetName()<<endl;;   

        G4double cross= Mottcross->GetTotalCross();


        if(cross == 0.0)return;
                
        G4ThreeVector dir = dp->GetMomentumDirection(); //old direction
        G4ThreeVector newDirection=Mottcross->GetNewDirection();//new direction
        newDirection.rotateUz(dir);   
  
        fParticleChange->ProposeMomentumDirection(newDirection);   
  
        //Recoil energy
        G4double trec= Mottcross->GetTrec();
        //Energy after scattering       
        G4double finalT = kinEnergy - trec;


        if(finalT <= lowEnergyLimit) { 
                trec = kinEnergy;  
                finalT = 0.0;
                } 
    
        fParticleChange->SetProposedKineticEnergy(finalT);

        G4double tcut = recoilThreshold;
        if(pCuts) { tcut= std::min(tcut,(*pCuts)[currentMaterialIndex]); 
                }
 

        if(trec > tcut) {

                //cout<<"Trec "<<trec/eV<<endl;
                G4ParticleDefinition* ion = theParticleTable->GetIon(iz, ia, 0.0);

                //incident before scattering
                G4double ptot=sqrt(Mottcross->GetMom2Lab());
                //incident after scattering
                G4double plab = sqrt(finalT*(finalT + 2.0*mass));
                G4ThreeVector p2 = (ptot*dir - plab*newDirection).unit();
                //secondary particle
                G4DynamicParticle* newdp  = new G4DynamicParticle(ion, p2, trec);
                        fvect->push_back(newdp);
                        }

        else if(trec > 0.0) {
                fParticleChange->ProposeNonIonizingEnergyDeposit(trec);
                if(trec< tcut) fParticleChange->ProposeLocalEnergyDeposit(trec);
                }


}

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