geant4/source/processes/electromagnetic/standard/src/G4eDPWACoulombScatteringModel.cc

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// -------------------------------------------------------------------
//
// GEANT4 Class header file
//
//
// File name:     G4eDPWACoulombScatteringModel
//
// Author:        Mihaly Novak
//
// Creation date: 02.07.2020
//
// Modifications:
//
// -------------------------------------------------------------------

#include "G4eDPWACoulombScatteringModel.hh"

#include "G4eDPWAElasticDCS.hh"
#include "G4ParticleChangeForGamma.hh"
#include "G4ParticleDefinition.hh"
#include "G4DataVector.hh"

#include "G4ProductionCutsTable.hh"
#include "G4Material.hh"
#include "G4Element.hh"
#include "G4ElementVector.hh"

#include "G4Electron.hh"

#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"
#include "G4ThreeVector.hh"


G4eDPWACoulombScatteringModel::G4eDPWACoulombScatteringModel(G4bool ismixed, G4bool isscpcor, G4double mumin)
: G4VEmModel("eDPWACoulombScattering"),
  fIsMixedModel(ismixed),
  fIsScpCorrection(isscpcor),
  fMuMin(mumin),
  fTheDCS(nullptr),
  fParticleChange(nullptr)
{
  SetLowEnergyLimit (  0.0*CLHEP::eV);  // ekin = 10 eV   is used if (E< 10  eV)
  SetHighEnergyLimit(100.0*CLHEP::MeV); // ekin = 100 MeV is used if (E>100 MeV)
}


G4eDPWACoulombScatteringModel::~G4eDPWACoulombScatteringModel()
{
  if (IsMaster()) {
    delete fTheDCS;
  }
}


void G4eDPWACoulombScatteringModel::Initialise(const G4ParticleDefinition* pdef,
                                               const G4DataVector& prodcuts)
{
  if(!fParticleChange) {
    fParticleChange = GetParticleChangeForGamma();
  }
  fMuMin        = 0.5*(1.0-std::cos(PolarAngleLimit()));
  fIsMixedModel = (fMuMin > 0.0);
  if(IsMaster()) {
    // clean the G4eDPWAElasticDCS object if any
    delete fTheDCS;
    fTheDCS = new G4eDPWAElasticDCS(pdef==G4Electron::Electron(), fIsMixedModel);
    // init only for the elements that are used in the geometry
    G4ProductionCutsTable* theCpTable = G4ProductionCutsTable::GetProductionCutsTable();
    G4int numOfCouples = (G4int)theCpTable->GetTableSize();
    for(G4int j=0; j<numOfCouples; ++j) {
      const G4Material* mat = theCpTable->GetMaterialCutsCouple(j)->GetMaterial();
      const G4ElementVector* elV = mat->GetElementVector();
      std::size_t numOfElem = mat->GetNumberOfElements();
      for (std::size_t ie = 0; ie < numOfElem; ++ie) {
        fTheDCS->InitialiseForZ((*elV)[ie]->GetZasInt());
      }
    }
    // init scattering power correction
    if (fIsScpCorrection) {
      fTheDCS->InitSCPCorrection(LowEnergyLimit(), HighEnergyLimit());
    }
    // will make use of the cross sections so the above needs to be done before
    InitialiseElementSelectors(pdef, prodcuts);
  }
}


void G4eDPWACoulombScatteringModel::InitialiseLocal(const G4ParticleDefinition*,
                                                    G4VEmModel* masterModel)
{
  SetElementSelectors(masterModel->GetElementSelectors());
  SetTheDCS(static_cast<G4eDPWACoulombScatteringModel*>(masterModel)->GetTheDCS());
}


G4double
G4eDPWACoulombScatteringModel::ComputeCrossSectionPerAtom(const G4ParticleDefinition*,
                                                          G4double ekin,
                                                          G4double Z,
                                                          G4double /*A*/,
                                                          G4double /*prodcut*/,
                                                          G4double /*emax*/)
{
  // Cross sections are computed by numerical integration of the pre-computed
  // DCS data between the muMin, muMax limits where mu(theta)=0.5[1-cos(theta)].
  // In case of single scattering model (i.e. when fMuMin=0): [muMin=0, muMax=1]
  // In case of mixed simulation model  (i.e. when fMuMin>0): [fMuMin , muMax=1]
  // NOTE: cross sections will be zero if the kinetic enrgy is out of the
  //       [10 eV-100 MeV] range for which DCS data has been computed.
  //
  G4double elCS  = 0.0;          // elastic cross section
  G4double tr1CS = 0.0;          // first transport cross section
  G4double tr2CS = 0.0;          // second transport cross section
  const G4double muMin = fMuMin;
  const G4double muMax = 1.0;
  fTheDCS->ComputeCSPerAtom((G4int)Z, ekin, elCS, tr1CS, tr2CS, muMin, muMax);
  // scattering power correction: should be only in condensed history ioni!
  if (fIsScpCorrection && CurrentCouple()) {
    const G4double theScpCor = fTheDCS->ComputeScatteringPowerCorrection(CurrentCouple(), ekin);
    elCS *= (theScpCor*(1.0+1.0/Z));
  }
  return std::max(0.0, elCS);
}


void
G4eDPWACoulombScatteringModel::SampleSecondaries(std::vector<G4DynamicParticle*>*,
                                                 const G4MaterialCutsCouple* cp,
                                                 const G4DynamicParticle* dp,
                                                 G4double, G4double)
{
  const G4double    ekin   = dp->GetKineticEnergy();
  const G4double    lekin  = dp->GetLogKineticEnergy();
  const G4Element*  target = SelectTargetAtom(cp, dp->GetParticleDefinition(), ekin, lekin);
  const G4int       izet   = target->GetZasInt();
  // sample cosine of the polar scattering angle in (hard) elastic insteraction
  CLHEP::HepRandomEngine* rndmEngine = G4Random::getTheEngine();
  G4double cost = 1.0;
  if (!fIsMixedModel) {
    G4double rndm[3];
    rndmEngine->flatArray(3, rndm);
    cost = fTheDCS->SampleCosineTheta(izet, lekin, rndm[0], rndm[1], rndm[2]);
  } else {
    //sample cost between costMax,costMin where costMax = 1-2xfMuMin;
    const G4double costMax = 1.0-2.0*fMuMin;
    const G4double costMin = -1.0;
    G4double rndm[2];
    rndmEngine->flatArray(2, rndm);
    cost = fTheDCS->SampleCosineThetaRestricted(izet, lekin, rndm[0], rndm[1], costMin, costMax);
  }
  // compute the new direction in the scattering frame
  const G4double sint = std::sqrt((1.0-cost)*(1.0+cost));
  const G4double phi  = CLHEP::twopi*rndmEngine->flat();
  G4ThreeVector theNewDirection(sint*std::cos(phi), sint*std::sin(phi), cost);
  // get original direction in lab frame and rotate new direction to lab frame
  G4ThreeVector theOrgDirectionLab = dp->GetMomentumDirection();
  theNewDirection.rotateUz(theOrgDirectionLab);
  // set new direction
  fParticleChange->ProposeMomentumDirection(theNewDirection);
}