G4NeutronElasticXS.cc

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// $Id$
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:    G4NeutronElasticXS
//
// Author  Ivantchenko, Geant4, 3-Aug-09
//
// Modifications:
//

#include "G4HadronicException.hh"
#include "G4NeutronElasticXS.hh"
#include "G4Neutron.hh"
#include "G4DynamicParticle.hh"
#include "G4Element.hh"
#include "G4ElementTable.hh"
#include "G4PhysicsLogVector.hh"
#include "G4PhysicsVector.hh"
#include "G4GlauberGribovCrossSection.hh"
#include "G4HadronNucleonXsc.hh"
#include "G4NistManager.hh"
#include "G4Proton.hh"

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

using namespace std;

G4NeutronElasticXS::G4NeutronElasticXS() 
 : G4VCrossSectionDataSet("G4NeutronElasticXS"),
   proton(G4Proton::Proton()), maxZ(92)
{
  //  verboseLevel = 0;
  if(verboseLevel > 0){
    G4cout  << "G4NeutronElasticXS::G4NeutronElasticXS Initialise for Z < " 
            << maxZ + 1 << G4endl;
  }
  data.resize(maxZ+1, 0);
  coeff.resize(maxZ+1, 1.0);
  ggXsection = new G4GlauberGribovCrossSection();
  fNucleon = new G4HadronNucleonXsc();
  isInitialized = false;
}

G4NeutronElasticXS::~G4NeutronElasticXS()
{
  delete fNucleon;
  for(G4int i=0; i<=maxZ; ++i) {
    delete data[i];
  }
}

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 > maxZ) { return xs; }

  G4int Amean = G4int(G4NistManager::Instance()->GetAtomicMassAmu(Z)+0.5);
  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(isInitialized) { return; }
  if(verboseLevel > 0){
    G4cout << "G4NeutronElasticXS::BuildPhysicsTable for " 
           << p.GetParticleName() << G4endl;
  }
  if(p.GetParticleName() != "neutron") { 
    throw G4HadronicException(__FILE__, __LINE__,"Wrong particle type");
    return; 
  }
  isInitialized = true;

  // check environment variable 
  // Build the complete string identifying the file with the data set
  char* path = getenv("G4NEUTRONXSDATA");
  if (!path){
    throw G4HadronicException(__FILE__, __LINE__, 
                              "G4NEUTRONXSDATA environment variable not defined");
    return;
  }

  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 > maxZ) { Z = maxZ; }
      //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) {
      throw G4HadronicException(__FILE__, __LINE__, 
                                "G4NEUTRONXSDATA environment variable not defined");
      return;
    }
  }
  G4DynamicParticle* dynParticle = dp;
  if(!dp) {
    dynParticle = 
      new G4DynamicParticle(G4Neutron::Neutron(),G4ThreeVector(1,0,0),1);
  }

  G4int Amean = G4int(G4NistManager::Instance()->GetAtomicMassAmu(Z)+0.5);

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

  std::ostringstream ost;
  ost << path << "/elast" << Z ;
  std::ifstream filein(ost.str().c_str());
  if (!(filein)) {
    G4cout << ost.str() 
           << "  is not opened by G4NeutronElasticXS" << G4endl;
    throw G4HadronicException(__FILE__, __LINE__,"NO data sets opened");
    return;
  }else{
    if(verboseLevel > 1) {
      G4cout << "file " << ost.str() 
             << " is opened by G4NeutronElasticXS" << G4endl;
    }
    
    // retrieve data from DB
    data[Z]->Retrieve(filein, true);
    
    // 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; }
}

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