G4NeutronElasticXS.cc

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// $Id: G4NeutronElasticXS.cc 93682 2015-10-28 10:09:49Z 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;

std::vector<G4PhysicsVector*>* G4NeutronElasticXS::data = 0;
G4double G4NeutronElasticXS::coeff[] = {0.0};

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] = 0;
    }
    delete data;
    data = 0;
  }
}

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"
          << "G4NeutronElasticXS is valid for energies up to 20 MeV, for all\n"
          << "targets through U.\n";  
}

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

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

  if(Z < 1 || Z >=MAXZEL) { return xs; }

  G4int Amean = G4lrint(G4NistManager::Instance()->GetAtomicMassAmu(Z));
  G4PhysicsVector* pv = (*data)[Z];
  //  G4cout  << "G4NeutronElasticXS::GetCrossSection e= " << ekin 
  // << " Z= " << Z << G4endl;

  // element was not initialised
  if(!pv) {
    Initialise(Z);
    pv = (*data)[Z];
    if(!pv) { return xs; }
  }

  G4double e1 = pv->Energy(0);
  if(ekin <= e1) { return (*pv)[0]; }

  G4int n = pv->GetVectorLength() - 1;
  G4double e2 = pv->Energy(n);

  if(ekin <= e2) { 
    xs = pv->Value(ekin); 
  } else if(1 == Z) { 
    fNucleon->GetHadronNucleonXscPDG(aParticle, proton);
    xs = coeff[1]*fNucleon->GetElasticHadronNucleonXsc();
  } else {          
    ggXsection->GetIsoCrossSection(aParticle, Z, Amean);
    xs = coeff[Z]*ggXsection->GetElasticGlauberGribovXsc();
  }

  if(verboseLevel > 0){
    G4cout  << "ekin= " << ekin << ",  XSinel= " << xs << 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(0 == coeff[0]) { 
    isMaster = true;
    for(G4int i=0; i<MAXZEL; ++i) { coeff[i] = 1.0; }
    data = new std::vector<G4PhysicsVector*>;
    data->resize(MAXZEL, 0);
  }

  // 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();
    if(numOfElm > 0) {
      for(size_t i=0; i<numOfElm; ++i) {
        G4int Z = G4int(((*theElmTable)[i])->GetZ());
        if(Z < 1)            { Z = 1; }
        else 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;
    }
  }
  G4DynamicParticle* dynParticle = dp;
  if(!dp) {
    dynParticle = 
      new G4DynamicParticle(G4Neutron::Neutron(),G4ThreeVector(1,0,0),1);
  }

  G4int Amean = G4lrint(G4NistManager::Instance()->GetAtomicMassAmu(Z));

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

  std::ostringstream ost;
  ost << path << "/elast" << 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 
    size_t n      = (*data)[Z]->GetVectorLength() - 1;
    G4double emax = (*data)[Z]->Energy(n);
    G4double sig1 = (*(*data)[Z])[n];
    dynParticle->SetKineticEnergy(emax);
    G4double sig2 = 0.0;
    if(1 == Z) {
      fNucleon->GetHadronNucleonXscPDG(dynParticle, proton);
      sig2 = fNucleon->GetElasticHadronNucleonXsc();
    } else {
      ggXsection->GetIsoCrossSection(dynParticle, Z, Amean);
      sig2 = ggXsection->GetElasticGlauberGribovXsc();
    }
    if(sig2 > 0.) { coeff[Z] = sig1/sig2; } 
  } 
  if(!dp) { delete dynParticle; }
}