G4NeutronElasticXS.cc

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// $Id: G4NeutronElasticXS.cc 110744 2018-06-12 06:35:40Z gcosmo $
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:    G4NeutronElasticXS
//
// Author  Ivantchenko, Geant4, 3-Aug-09
//
// Modifications:
//

#include "G4NeutronElasticXS.hh"
#include "G4Neutron.hh"
#include "G4DynamicParticle.hh"
#include "G4Element.hh"
#include "G4ElementTable.hh"
#include "G4PhysicsLogVector.hh"
#include "G4PhysicsVector.hh"
#include "G4ComponentGGHadronNucleusXsc.hh"
#include "G4HadronNucleonXsc.hh"
#include "G4NistManager.hh"
#include "G4Proton.hh"

#include <iostream>
#include <fstream>
#include <sstream>

// factory
#include "G4CrossSectionFactory.hh"
//
G4_DECLARE_XS_FACTORY(G4NeutronElasticXS);

using namespace std;

G4PhysicsVector* G4NeutronElasticXS::data[] = {nullptr};
G4double G4NeutronElasticXS::coeff[] = {1.0};

#ifdef G4MULTITHREADED
  G4Mutex G4NeutronElasticXS::neutronElasticXSMutex = G4MUTEX_INITIALIZER;
#endif

G4NeutronElasticXS::G4NeutronElasticXS() 
 : G4VCrossSectionDataSet(Default_Name()),
   proton(G4Proton::Proton())
{
  //  verboseLevel = 0;
  if(verboseLevel > 0){
    G4cout  << "G4NeutronElasticXS::G4NeutronElasticXS Initialise for Z < " 
      << MAXZEL << G4endl;
  }
  ggXsection = new G4ComponentGGHadronNucleusXsc();
  fNucleon = new G4HadronNucleonXsc();
  isMaster = false;
}

G4NeutronElasticXS::~G4NeutronElasticXS()
{
  delete fNucleon;
  delete ggXsection;
  if(isMaster) {
    for(G4int i=0; i<MAXZEL; ++i) {
      delete data[i];
      data[i] = nullptr;
    }
  }
}

void G4NeutronElasticXS::CrossSectionDescription(std::ostream& outFile) const
{
  outFile << "G4NeutronElasticXS calculates the neutron elastic scattering\n"
          << "cross section on nuclei using data from the high precision\n"
          << "neutron database.  These data are simplified and smoothed over\n"
          << "the resonance region in order to reduce CPU time.\n"
          << "For high energies Glauber-Gribiv cross section is used.\n";
}

G4bool 
G4NeutronElasticXS::IsElementApplicable(const G4DynamicParticle*, 
          G4int, const G4Material*)
{
  return true;
}

G4double 
G4NeutronElasticXS::GetElementCrossSection(const G4DynamicParticle* aParticle,
             G4int ZZ, const G4Material*)
{
  G4double xs = 0.0;
  G4double ekin = aParticle->GetKineticEnergy();

  G4int Z = (ZZ >= MAXZEL) ? MAXZEL - 1 : ZZ; 

  G4PhysicsVector* pv = data[Z];
  //  G4cout  << "G4NeutronElasticXS::GetCrossSection e= " << ekin 
  // << " Z= " << Z << G4endl;

  // element was not initialised
  if(!pv) { return xs; }

  if(ekin <= pv->Energy(0)) { return (*pv)[0]; }

  if(ekin <= pv->GetMaxEnergy()) { 
    xs = pv->Value(ekin); 
  } else if(1 == Z) { 
    fNucleon->GetHadronNucleonXscPDG(aParticle, proton);
    xs = coeff[1]*fNucleon->GetElasticHadronNucleonXsc();
  } else {          
    G4int Amean = 
      G4lrint(G4NistManager::Instance()->GetAtomicMassAmu(Z));
    ggXsection->GetIsoCrossSection(aParticle, Z, Amean);
    xs = coeff[Z]*ggXsection->GetElasticGlauberGribovXsc();
  }

  if(verboseLevel > 0){
    G4cout  << "Z= " << Z << " Ekin(MeV)= " << ekin/CLHEP::MeV 
      << ",  nElmXSel(bn)= " << xs/CLHEP::barn 
      << G4endl;
  }
  return xs;
}

void 
G4NeutronElasticXS::BuildPhysicsTable(const G4ParticleDefinition& p)
{
  if(verboseLevel > 0){
    G4cout << "G4NeutronElasticXS::BuildPhysicsTable for " 
     << p.GetParticleName() << G4endl;
  }
  if(p.GetParticleName() != "neutron") { 
    G4ExceptionDescription ed;
    ed << p.GetParticleName() << " is a wrong particle type -"
       << " only neutron is allowed";
    G4Exception("G4NeutronElasticXS::BuildPhysicsTable(..)","had012",
    FatalException, ed, "");
    return; 
  }

  if(!data[1]) { 
#ifdef G4MULTITHREADED
    G4MUTEXLOCK(&neutronElasticXSMutex);
    if(!data[1]) { 
#endif
      isMaster = true;
#ifdef G4MULTITHREADED
    }
    G4MUTEXUNLOCK(&neutronElasticXSMutex);
#endif
  }

  // it is possible re-initialisation for the second run
  if(isMaster) {

    // check environment variable 
    // Build the complete string identifying the file with the data set
    char* path = getenv("G4NEUTRONXSDATA");

    G4DynamicParticle* dynParticle = 
      new G4DynamicParticle(G4Neutron::Neutron(),G4ThreeVector(1,0,0),1);

    // Access to elements
    const G4ElementTable* theElmTable = G4Element::GetElementTable();
    size_t numOfElm = G4Element::GetNumberOfElements();
    for(size_t i=0; i<numOfElm; ++i) {
      G4int Z = ((*theElmTable)[i])->GetZasInt();
      if(Z >= MAXZEL) { Z = MAXZEL-1; }
      //G4cout << "Z= " << Z << G4endl;
      // Initialisation 
      if(!data[Z]) { Initialise(Z, dynParticle, path); }
    }
    delete dynParticle;
  }
}

void 
G4NeutronElasticXS::Initialise(G4int Z, G4DynamicParticle* dp, 
             const char* p)
{
  if(data[Z]) { return; }
  const char* path = p;
  if(!p) {
    // check environment variable 
    // Build the complete string identifying the file with the data set
    path = getenv("G4NEUTRONXSDATA");
    if (!path) {
      G4Exception("G4NeutronElasticXS::Initialise(..)","had013",
      FatalException,
                  "Environment variable G4NEUTRONXSDATA is not defined");
      return;
    }
  }

  // upload data from file
  data[Z] = new G4PhysicsLogVector();

  std::ostringstream ost;
  ost << path << "/neutron/el" << Z ;
  std::ifstream filein(ost.str().c_str());
  if (!(filein)) {
    G4ExceptionDescription ed;
    ed << "Data file <" << ost.str().c_str()
       << "> is not opened!";
    G4Exception("G4NeutronElasticXS::Initialise(..)","had014",
                FatalException, ed, "Check G4NEUTRONXSDATA");
    return;
  }else{
    if(verboseLevel > 1) {
      G4cout << "file " << ost.str() 
       << " is opened by G4NeutronElasticXS" << G4endl;
    }
    
    // retrieve data from DB
    if(!data[Z]->Retrieve(filein, true)) {
      G4ExceptionDescription ed;
      ed << "Data file <" << ost.str().c_str()
   << "> is not retrieved!";
      G4Exception("G4NeutronElasticXS::Initialise(..)","had015",
      FatalException, ed, "Check G4NEUTRONXSDATA");
      return;
    }
    
    // smooth transition 
    G4double sig1 = (*(data[Z]))[data[Z]->GetVectorLength()-1];
    dp->SetKineticEnergy(data[Z]->GetMaxEnergy());
    G4double sig2 = 0.0;
    if(1 == Z) {
      fNucleon->GetHadronNucleonXscPDG(dp, proton);
      sig2 = fNucleon->GetElasticHadronNucleonXsc();
    } else {
      G4int Amean = 
  G4lrint(G4NistManager::Instance()->GetAtomicMassAmu(Z));
      ggXsection->GetIsoCrossSection(dp, Z, Amean);
      sig2 = ggXsection->GetElasticGlauberGribovXsc();
    }
    if(sig2 > 0.) { coeff[Z] = sig1/sig2; } 
  } 
}