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 "G4UnitsTable.hh"

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using namespace std;

G4IonCoulombScatteringModel::G4IonCoulombScatteringModel(const G4String& nam)
  : G4VEmModel(nam),

    cosThetaMin(1.0),
    isInitialised(false)
{
        fNistManager = G4NistManager::Instance();
        theParticleTable = G4ParticleTable::GetParticleTable();
        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&  )
{
        SetupParticle(p);
        currentCouple = 0;
        currentMaterialIndex = -1;
        cosThetaMin = cos(PolarAngleLimit());
        ioncross->Initialise(p,cosThetaMin);
 
        pCuts = 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) return cross;

        DefineMaterial(CurrentCouple());

        G4int iz          = G4int(Z);

        //from lab to pCM & mu_rel of effective particle
        ioncross->SetupKinematic(kinEnergy, cutEnergy,iz);


        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);



        G4double cross= ComputeCrossSectionPerAtom(particle,kinEnergy, Z,
                                kinEnergy, cutEnergy, kinEnergy) ;
        if(cross == 0.0) { return; }
    
        //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();


        // kinematics in the Lab system
        G4double etot = kinEnergy + mass;
        G4double mom2=  kinEnergy*(kinEnergy+2.0*mass);
        G4double ptot = sqrt(mom2);

        //CM particle 1
        G4double bet  = ptot/(etot + mass2);
        G4double gam  = 1.0/sqrt((1.0 - bet)*(1.0 + bet));

        //CM    
        G4double momCM2= ioncross->GetMomentum2();
        G4double momCM =std::sqrt(momCM2); 
        //energy & momentum after scattering of incident particle
        G4double pxCM = momCM*sint*cos(phi);
        G4double pyCM = momCM*sint*sin(phi);
        G4double pzCM = momCM*cost;
        G4double eCM  = sqrt(momCM2 + mass*mass);

        //CM--->Lab
        G4ThreeVector v1(pxCM , pyCM, gam*(pzCM + bet*eCM));
        G4ThreeVector dir = dp->GetMomentumDirection(); 

        G4ThreeVector newDirection = v1.unit();
        newDirection.rotateUz(dir);   
  
        fParticleChange->ProposeMomentumDirection(newDirection);   
  
        // V.Ivanchenko fix of final energies after scattering
        // recoil.......................................
        //G4double trec =(1.0 - cost)* mass2*(etot*etot - mass*mass )/
        //                      (mass*mass + mass2*mass2+ 2.*mass2*etot);
        //G4double finalT = kinEnergy - trec;

        // new computation
        G4double finalT = gam*(eCM + bet*pzCM) - mass;
        G4double trec = kinEnergy - finalT;

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

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

                        //G4cout<<" tcut eV "<<tcut/eV<<endl;
                        }
 
        if(trec > tcut) {
                G4ParticleDefinition* ion = theParticleTable->GetIon(iz, ia, 0.0);
                G4double plab = sqrt(finalT*(finalT + 2.0*mass));
                G4ThreeVector p2 = (ptot*dir - plab*newDirection).unit();
                G4DynamicParticle* newdp  = new G4DynamicParticle(ion, p2, trec);
                        fvect->push_back(newdp);
        } else if(trec > 0.0) {
                fParticleChange->ProposeLocalEnergyDeposit(trec);
                fParticleChange->ProposeNonIonizingEnergyDeposit(trec);
        }


}

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