G4DensityEffectCalculator Class Reference

#include <G4DensityEffectCalculator.hh>

Public Member Functions
	G4DensityEffectCalculator (const G4Material *, G4int)
	~G4DensityEffectCalculator ()
G4double	ComputeDensityCorrection (G4double x)

Detailed Description

Definition at line 53 of file G4DensityEffectCalculator.hh.

Constructor & Destructor Documentation

G4DensityEffectCalculator()

G4DensityEffectCalculator::G4DensityEffectCalculator	(	const G4Material *	mat,
		G4int	n
	)

Definition at line 56 of file G4DensityEffectCalculator.cc.

  : fMaterial(mat), fVerbose(0), fWarnings(0), nlev(n)
{
  fVerbose = std::max(fVerbose, G4NistManager::Instance()->GetVerbose());
 
  sternf    = new G4double [nlev];
  levE      = new G4double [nlev];
  sternl    = new G4double [nlev];
  sternEbar = new G4double [nlev];
  for(G4int i=0; i<nlev; ++i) {
    sternf[i]    = 0.0;
    levE[i]      = 0.0;
    sternl[i]    = 0.0;
    sternEbar[i] = 0.0;
  }
 
  fConductivity = sternx = 0.0;
  G4bool conductor = (fMaterial->GetFreeElectronDensity() > 0.0);
 
  G4int sh = 0;
  G4double sum = 0.;
  const G4double tot = fMaterial->GetTotNbOfAtomsPerVolume();
  for(size_t j = 0; j < fMaterial->GetNumberOfElements(); ++j) {
    // The last subshell is considered to contain the conduction
    // electrons. Sternheimer 1984 says "the lowest chemical valance of
    // the element" is used to set the number of conduction electrons.
    // I'm not sure if that means the highest subshell or the whole
    // shell, but in any case, he also says that the choice is arbitrary
    // and offers a possible alternative. This is one of the sources of
    // uncertainty in the model.
    const G4double frac = fMaterial->GetVecNbOfAtomsPerVolume()[j]/tot;
    const G4int Z = fMaterial->GetElement(j)->GetZasInt();
    const G4int nshell = G4AtomicShells::GetNumberOfShells(Z);
    for(G4int i = 0; i < nshell; ++i) {
      // For conductors, put *all* top shell electrons into the conduction
      // band, regardless of element.
      const G4double xx = frac*G4AtomicShells::GetNumberOfElectrons(Z, i);
      if(i < nshell-1 || !conductor) {
    sternf[sh] += xx;
      } else {
        fConductivity += xx;
      }
      levE[sh] = G4AtomicShells::GetBindingEnergy(Z, i)/CLHEP::eV;
      ++sh;
    }
  }
  for(G4int i=0; i<nlev; ++i) {
    sum += sternf[i];
  }
  sum = (sum > 0.0) ? 1./sum : 0.0;
  for(G4int i=0; i<nlev; ++i) {
    sternf[i] *= sum;
  }
  plasmaE = fMaterial->GetIonisation()->GetPlasmaEnergy()/CLHEP::eV;
  meanexcite = fMaterial->GetIonisation()->GetMeanExcitationEnergy()/CLHEP::eV;
}

~G4DensityEffectCalculator()

G4DensityEffectCalculator::~G4DensityEffectCalculator

(

)

Definition at line 113 of file G4DensityEffectCalculator.cc.

{
  delete [] sternf;
  delete [] levE;
  delete [] sternl;
  delete [] sternEbar;
}

Member Function Documentation

ComputeDensityCorrection()

G4double G4DensityEffectCalculator::ComputeDensityCorrection

(

G4double

x

)

Definition at line 121 of file G4DensityEffectCalculator.cc.

{
  if(fVerbose > 1) {
    G4cout << "G4DensityEffectCalculator::ComputeDensityCorrection for " 
           << fMaterial->GetName() << ", x= " << x << G4endl;
  }
  const G4double approx = fMaterial->GetIonisation()->GetDensityCorrection(x);
  const G4double exact  = FermiDeltaCalculation(x);
 
  if(fVerbose > 1) {
    G4cout << "   Delta: computed= " << exact 
       << ", parametrized= " << approx << G4endl;
  }
  if(approx > 0. && exact < 0.) {
    if(fVerbose > 0) {
      ++fWarnings;
      if(fWarnings < maxWarnings) {
        G4ExceptionDescription ed; 
        ed << "Sternheimer fit failed for " << fMaterial->GetName() 
       << ", x = " << x << ": Delta exact= "
       << exact << ", approx= " << approx;
    G4Exception("G4DensityEffectCalculator::DensityCorrection", "mat008", 
                    JustWarning, ed);
      }
    }
    return approx;
  }
  // Fall back to approx if exact and approx are very different, under the
  // assumption that this means the exact calculation has gone haywire
  // somehow, with the exception of the case where approx is negative.  I
  // have seen this clearly-wrong result occur for substances with extremely
  // low density (1e-25 g/cc).
  if(approx >= 0. && std::abs(exact - approx) > 1.) {
    if(fVerbose > 0) {
      ++fWarnings;
      if(fWarnings < maxWarnings) {
        G4ExceptionDescription ed; 
        ed << "Sternheimer exact= " << exact << " and approx= "
           << approx << " are too different for "
           << fMaterial->GetName() << ", x = " << x;
    G4Exception("G4DensityEffectCalculator::DensityCorrection", "mat008", 
                    JustWarning, ed);
      }
    }
    return approx;
  }
  return exact;
}

Referenced by G4IonisParamMat::DensityCorrection().

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The documentation for this class was generated from the following files:

• G4DensityEffectCalculator.hh
• G4DensityEffectCalculator.cc