G4JAEAElasticScatteringModel.cc

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/*
  Authors:
 
  Updated 15 November 2019
 
  Updates:
  1. Change reading method for cross section data.
  2. Add warning not to use with polarized photons.
 
  M. Omer and R. Hajima  on   17 October 2016
  contact:
  [email protected] and [email protected]
  Publication Information:
  1- M. Omer, R. Hajima, Including Delbrück scattering in Geant4,
  Nucl. Instrum. Methods Phys. Res. Sect. B, vol. 405, 2017, pp. 43-49.,
  https://doi.org/10.1016/j.nimb.2017.05.028
  2- M. Omer, R. Hajima, Geant4 physics process for elastic scattering of gamma-rays,
  JAEA Technical Report 2018-007, 2018.
  https://doi.org/10.11484/jaea-data-code-2018-007
*/
#include "G4JAEAElasticScatteringModel.hh"
#include "G4AutoLock.hh"
#include "G4SystemOfUnits.hh"
 
using namespace std;
namespace { G4Mutex G4JAEAElasticScatteringModelMutex = G4MUTEX_INITIALIZER; }
 
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G4PhysicsFreeVector* G4JAEAElasticScatteringModel::dataCS[]={nullptr} ;
G4DataVector* G4JAEAElasticScatteringModel::ES_Data[]={nullptr};
 
G4JAEAElasticScatteringModel::G4JAEAElasticScatteringModel()
  :G4VEmModel("G4JAEAElasticScatteringModel"),isInitialised(false)
{
  fParticleChange = nullptr;
  //Low energy limit for G4JAEAElasticScatteringModel process.
  lowEnergyLimit  = 10 * keV;
 
  verboseLevel= 0;
  // Verbosity scale for debugging purposes:
  // 0 = nothing
  // 1 = calculation of cross sections, file openings...
  // 2 = entering in methods
 
  if(verboseLevel > 0)
    {
      G4cout << "G4JAEAElasticScatteringModel is constructed " << G4endl;
    }
}
 
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G4JAEAElasticScatteringModel::~G4JAEAElasticScatteringModel()
{
  if(IsMaster()) {
    for(G4int i=0; i<=maxZ; ++i) {
      if(dataCS[i]) {
    delete dataCS[i];
    dataCS[i] = nullptr;
      }
      if (ES_Data[i]){
    delete ES_Data[i];
    ES_Data[i] = nullptr;
      }
    }
  }
}
 
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void G4JAEAElasticScatteringModel::Initialise(const G4ParticleDefinition* particle,
                          const G4DataVector& cuts)
{
  if (verboseLevel > 1)
    {
      G4cout << "Calling Initialise() of G4JAEAElasticScatteringModel." << G4endl
         << "Energy range: "
         << LowEnergyLimit() / eV << " eV - "
         << HighEnergyLimit() / GeV << " GeV"
         << G4endl;
    }
 
  if(IsMaster()) {
    // Initialise element selector
    InitialiseElementSelectors(particle, cuts);
 
    // Access to elements
    const char* path = G4FindDataDir("G4LEDATA");
    G4ProductionCutsTable* theCoupleTable =
      G4ProductionCutsTable::GetProductionCutsTable();
    G4int numOfCouples = (G4int)theCoupleTable->GetTableSize();
 
    for(G4int i=0; i<numOfCouples; ++i)
      {
    const G4MaterialCutsCouple* couple =
      theCoupleTable->GetMaterialCutsCouple(i);
    const G4Material* material = couple->GetMaterial();
    const G4ElementVector* theElementVector = material->GetElementVector();
    std::size_t nelm = material->GetNumberOfElements();
 
    for (std::size_t j=0; j<nelm; ++j)
      {
        G4int Z = G4lrint((*theElementVector)[j]->GetZ());
        if(Z < 1)          { Z = 1; }
        else if(Z > maxZ)  { Z = maxZ; }
        if( (!dataCS[Z]) ) { ReadData(Z, path); }
      }
      }
  }
 
  if(isInitialised) { return; }
  fParticleChange = GetParticleChangeForGamma();
  isInitialised = true;
 
}
 
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void G4JAEAElasticScatteringModel::InitialiseLocal(const G4ParticleDefinition*,
                           G4VEmModel* masterModel)
{
  SetElementSelectors(masterModel->GetElementSelectors());
}
 
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void G4JAEAElasticScatteringModel::ReadData(std::size_t Z, const char* path)
{
  if (verboseLevel > 1)
    {
      G4cout << "Calling ReadData() of G4JAEAElasticScatteringModel"
         << G4endl;
    }
 
  if(dataCS[Z]) { return; }
 
  const char* datadir = path;
 
  if(!datadir)
    {
      datadir = G4FindDataDir("G4LEDATA");
      if(!datadir)
    {
      G4Exception("G4JAEAElasticScatteringModel::ReadData()","em0006",
              FatalException,
              "Environment variable G4LEDATA not defined");
      return;
    }
    }
 
  /* Reading all data in the form of 183 * 300 array.
     The first row is the energy, and the second row is the total cross section.
     Rows from the 3rd to the 183rd are the differential cross section with an angular 
     resolution of 1 degree.
  */
  std::ostringstream ostCS;
  ostCS << datadir << "/JAEAESData/amp_Z_" << Z ;
  std::ifstream ES_Data_Buffer(ostCS.str().c_str(),ios::binary);
  if( !ES_Data_Buffer.is_open() )
    {
      G4ExceptionDescription ed;
      ed << "G4JAEAElasticScattertingModel data file <" << ostCS.str().c_str()
     << "> is not opened!" << G4endl;
      G4Exception("G4JAEAElasticScatteringModel::ReadData()","em0003",FatalException,
          ed,
          "G4LEDATA version should be G4EMLOW7.11 or later. Elastic Scattering Data are not loaded");
      return;
    }
  else
    {
      if(verboseLevel > 3) {
    G4cout << "File " << ostCS.str()
           << " is opened by G4JAEAElasticScatteringModel" << G4endl;
      }
    }
  if (!ES_Data[Z])
    ES_Data[Z] = new G4DataVector();
   
  G4float buffer_var;
  while (ES_Data_Buffer.read(reinterpret_cast<char*>(&buffer_var),sizeof(float)))
    {
      ES_Data[Z]->push_back(buffer_var);
    }
 
  /*
    Writing the total cross section data to a G4PhysicsFreeVector.
    This provides an interpolation of the Energy-Total Cross Section data.
  */
 
  dataCS[Z] = new G4PhysicsFreeVector(300,0.01,3.,/*spine=*/true);
  //Note that the total cross section and energy are converted to the internal units.
  for (G4int i=0;i<300;++i)
    dataCS[Z]->PutValues(i,10.*i*1e-3,ES_Data[Z]->at(i)*1e-22);
 
  // Activation of spline interpolation
  dataCS[Z] ->FillSecondDerivatives();
  
}
 
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G4double G4JAEAElasticScatteringModel::ComputeCrossSectionPerAtom(
                                  const G4ParticleDefinition*,
                                  G4double GammaEnergy,
                                  G4double Z, G4double,
                                  G4double, G4double)
{
  if (verboseLevel > 2)
    {
      G4cout << "G4JAEAElasticScatteringModel::ComputeCrossSectionPerAtom()"
         << G4endl;
    }
 
  if(GammaEnergy < lowEnergyLimit) { return 0.0; }
 
  G4double xs = 0.0;
 
  G4int intZ = G4lrint(Z);
 
  if(intZ < 1 || intZ > maxZ) { return xs; }
 
  G4PhysicsFreeVector* pv = dataCS[intZ];
 
  // if element was not initialised
  // do initialisation safely for MT mode
  if(!pv) {
    InitialiseForElement(0, intZ);
    pv = dataCS[intZ];
    if(!pv) { return xs; }
  }
 
  G4int n = G4int(pv->GetVectorLength() - 1);
 
  G4double e = GammaEnergy;
  if(e >= pv->Energy(n)) {
    xs = (*pv)[n];
  } else if(e >= pv->Energy(0)) {
    xs = pv->Value(e);
  }
 
  if(verboseLevel > 0)
    {
      G4cout  <<  "****** DEBUG: tcs value for Z=" << Z << " at energy (MeV)="
          << e << G4endl;
      G4cout  <<  "  cs (Geant4 internal unit)=" << xs << G4endl;
      G4cout  <<  "    -> first E*E*cs value in CS data file (iu) =" << (*pv)[0]
          << G4endl;
      G4cout  <<  "    -> last  E*E*cs value in CS data file (iu) =" << (*pv)[n]
          << G4endl;
      G4cout  <<  "*********************************************************"
          << G4endl;
    }
 
  return (xs);
}
 
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void G4JAEAElasticScatteringModel::SampleSecondaries(
                             std::vector<G4DynamicParticle*>*,
                             const G4MaterialCutsCouple* couple,
                             const G4DynamicParticle* aDynamicGamma,
                             G4double, G4double)
{
  if (verboseLevel > 2) {
    G4cout << "Calling SampleSecondaries() of G4JAEAElasticScatteringModel."
       << G4endl;
  }
 
  G4double photonEnergy0 = aDynamicGamma->GetKineticEnergy();
 
  // Absorption of low-energy gamma
  if (photonEnergy0 <= lowEnergyLimit)
    {
      fParticleChange->ProposeTrackStatus(fStopAndKill);
      fParticleChange->SetProposedKineticEnergy(0.);
      fParticleChange->ProposeLocalEnergyDeposit(photonEnergy0);
      return;
    }
 
  //Warning if the incoming photon has polarization
  G4double Xi1=0, Xi2=0, Xi3=0;
  G4ThreeVector gammaPolarization0 = aDynamicGamma->GetPolarization();
  Xi1=gammaPolarization0.x();
  Xi2=gammaPolarization0.y();
  Xi3=gammaPolarization0.z();
 
  G4double polarization_magnitude=Xi1*Xi1+Xi2*Xi2+Xi3*Xi3;
  if ((polarization_magnitude)>0 || (Xi1*Xi1>0) || (Xi2*Xi2>0) || (Xi3*Xi3>0))
    {
      G4cout<<"WARNING: G4JAEAElasticScatteringModel is only compatible with non-polarized photons."
        <<G4endl;
      G4cout<<"The event is ignored."<<G4endl;
      return;
    }
 
  // Select randomly one element in the current material
  const G4ParticleDefinition* particle =  aDynamicGamma->GetDefinition();
  const G4Element* elm = SelectRandomAtom(couple,particle,photonEnergy0);
  G4int Z = G4lrint(elm->GetZ());
 
  G4int energyindex=round(100*photonEnergy0)-1;
  /*
    Getting the normalized probablity distrbution function and
    normalization factor to create the probability distribution function
  */
  G4double a1=0, a2=0, a3=0,a4=0;
  G4double normdist=0;
  for (G4int i=0;i<=180;++i)
    {
      a1=ES_Data[Z]->at(4*i+300+181*4*(energyindex));
      a2=ES_Data[Z]->at(4*i+1+300+181*4*(energyindex));
      a3=ES_Data[Z]->at(4*i+2+300+181*4*(energyindex));
      a4=ES_Data[Z]->at(4*i+3+300+181*4*(energyindex));
      distribution[i]=a1*a1+a2*a2+a3*a3+a4*a4;
      normdist += distribution[i];
    }
 
  //Create the cummulative distribution function (cdf)
  for (G4int i =0;i<=180;++i)
    pdf[i]=distribution[i]/normdist;
  cdf[0]=0;
  G4double cdfsum =0;
  for (G4int i=0; i<=180;++i)
    {
      cdfsum=cdfsum+pdf[i];
      cdf[i]=cdfsum;
    }
  //Sampling the polar angle by inverse transform uing cdf.
  G4double r = G4UniformRand();
  G4double *cdfptr=lower_bound(cdf,cdf+181,r);
  G4int cdfindex = (G4int)(cdfptr-cdf-1);
  G4double cdfinv = (r-cdf[cdfindex])/(cdf[cdfindex+1]-cdf[cdfindex]);
  G4double theta = (cdfindex+cdfinv)/180.;
  //polar is now ready
  theta = theta*CLHEP::pi;
 
  
  /* Alternative sampling using CLHEP functions
     CLHEP::RandGeneral GenDistTheta(distribution,181);
     G4double theta = CLHEP::pi*GenDistTheta.shoot();
     theta =theta*CLHEP::pi;        //polar is now ready
  */
 
  //Azimuth is uniformally distributed
  G4double phi  = CLHEP::twopi*G4UniformRand();
 
  G4ThreeVector finaldirection(sin(theta)*cos(phi), sin(theta)*sin(phi), cos(theta));
  finaldirection.rotateUz(aDynamicGamma->GetMomentumDirection());
  //Sampling the Final State
  fParticleChange->ProposeMomentumDirection(finaldirection);
  fParticleChange->SetProposedKineticEnergy(photonEnergy0);
}
 
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void
G4JAEAElasticScatteringModel::InitialiseForElement(const G4ParticleDefinition*,
                           G4int Z)
{
  G4AutoLock l(&G4JAEAElasticScatteringModelMutex);
  if(!dataCS[Z]) { ReadData(Z); }
  l.unlock();
}
 
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