G4EmSaturation.cc

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// $Id$
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4EmSaturation
//
// Author:        Vladimir Ivanchenko
//
// Creation date: 18.02.2008
//
// Modifications:
//
// -------------------------------------------------------------

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#include "G4EmSaturation.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4LossTableManager.hh"
#include "G4NistManager.hh"
#include "G4Material.hh"
#include "G4MaterialCutsCouple.hh"
#include "G4Electron.hh"
#include "G4Proton.hh"

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G4EmSaturation::G4EmSaturation()
{
  verbose = 1;
  manager = 0;

  curMaterial = 0;
  curBirks    = 0.0;
  curRatio    = 1.0;
  curChargeSq = 1.0;
  nMaterials  = 0;

  electron = 0;
  proton   = 0;
  nist     = G4NistManager::Instance();

  Initialise(); 
}

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G4EmSaturation::~G4EmSaturation()
{}

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G4double G4EmSaturation::VisibleEnergyDeposition(
                                      const G4ParticleDefinition* p, 
                                      const G4MaterialCutsCouple* couple, 
                                      G4double length,
                                      G4double edep,
                                      G4double niel)
{
  if(edep <= 0.0) { return 0.0; }

  G4double evis = edep;
  G4double bfactor = FindBirksCoefficient(couple->GetMaterial());

  if(bfactor > 0.0) { 

    G4int pdgCode = p->GetPDGEncoding();
    // atomic relaxations for gamma incident
    if(22 == pdgCode) {
      evis /= (1.0 + bfactor*edep/manager->GetRange(electron,edep,couple));

      // energy loss
    } else {

      // protections
      G4double nloss = niel;
      if(nloss < 0.0) nloss = 0.0;
      G4double eloss = edep - nloss;

      // neutrons
      if(2112 == pdgCode || eloss < 0.0 || length <= 0.0) {
        nloss = edep;
        eloss = 0.0;
      }

      // continues energy loss
      if(eloss > 0.0) { eloss /= (1.0 + bfactor*eloss/length); }
 
      // non-ionizing energy loss
      if(nloss > 0.0) {
        if(!proton) { proton = G4Proton::Proton(); }
        G4double escaled = nloss*curRatio;
        G4double range = manager->GetRange(proton,escaled,couple)/curChargeSq; 
        nloss /= (1.0 + bfactor*nloss/range);
      }

      evis = eloss + nloss;
    }
  }
  
  return evis;
}

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G4double G4EmSaturation::FindG4BirksCoefficient(const G4Material* mat)
{
  G4String name = mat->GetName();
  // is this material in the vector?
  
  for(G4int j=0; j<nG4Birks; ++j) {
    if(name == g4MatNames[j]) {
      if(verbose > 0) 
        G4cout << "### G4EmSaturation::FindG4BirksCoefficient for "
               << name << " is " << g4MatData[j]*MeV/mm << " mm/MeV "
               << G4endl;
      return g4MatData[j];
    }
  }
  return FindBirksCoefficient(mat);
}

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G4double G4EmSaturation::FindBirksCoefficient(const G4Material* mat)
{
  // electron should exist in any case
  if(!manager) {
    manager = G4LossTableManager::Instance();
    electron= G4Electron::Electron();
  }

  if(mat == curMaterial) { return curBirks; }

  curMaterial = mat;
  curBirks = 0.0;
  curRatio = 1.0;
  curChargeSq = 1.0;

  // seach in the run-time list
  for(G4int i=0; i<nMaterials; ++i) {
    if(mat == matPointers[i]) {
      curBirks = mat->GetIonisation()->GetBirksConstant();
      curRatio = massFactors[i];
      curChargeSq = effCharges[i];
      return curBirks;
    }
  }

  G4String name = mat->GetName();
  curBirks = mat->GetIonisation()->GetBirksConstant();

  // material has no Birks coeffitient defined
  // seach in the Geant4 list
  if(curBirks == 0.0) {
    for(G4int j=0; j<nG4Birks; ++j) {
      if(name == g4MatNames[j]) {
        mat->GetIonisation()->SetBirksConstant(g4MatData[j]);
        curBirks = g4MatData[j];
        break;
      }
    }
  }

  if(curBirks == 0.0 && verbose > 0) {
      G4cout << "### G4EmSaturation::FindBirksCoefficient fails "
        " for material " << name << G4endl;
  }

  // compute mean mass ratio
  curRatio = 0.0;
  curChargeSq = 0.0;
  G4double norm = 0.0;
  const G4ElementVector* theElementVector = mat->GetElementVector();
  const G4double* theAtomNumDensityVector = mat->GetVecNbOfAtomsPerVolume();
  size_t nelm = mat->GetNumberOfElements();
  for (size_t i=0; i<nelm; ++i) {
    const G4Element* elm = (*theElementVector)[i];
    G4double Z = elm->GetZ();
    G4double w = Z*Z*theAtomNumDensityVector[i];
    curRatio += w/nist->GetAtomicMassAmu(G4int(Z));
    curChargeSq = Z*Z*w;
    norm += w;
  }
  curRatio *= proton_mass_c2/norm;
  curChargeSq /= norm;

  // store results
  matPointers.push_back(mat);
  matNames.push_back(name);
  massFactors.push_back(curRatio);
  effCharges.push_back(curChargeSq);
  nMaterials++;
  if(curBirks > 0.0 && verbose > 0) {
    G4cout << "### G4EmSaturation::FindBirksCoefficient Birks coefficient for "
           << name << "  " << curBirks*MeV/mm << " mm/MeV" << G4endl;
  }
  return curBirks;
}

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void G4EmSaturation::DumpBirksCoefficients()
{
  if(nMaterials > 0) {
    G4cout << "### Birks coeffitients used in run time" << G4endl;
    for(G4int i=0; i<nMaterials; ++i) {
      G4double br = matPointers[i]->GetIonisation()->GetBirksConstant();
      G4cout << "   " << matNames[i] << "     " 
             << br*MeV/mm << " mm/MeV" << "     "
             << br*matPointers[i]->GetDensity()*MeV*cm2/g 
             << " g/cm^2/MeV" 
             << G4endl;
    }
  }
}

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void G4EmSaturation::DumpG4BirksCoefficients()
{
  if(nG4Birks > 0) {
    G4cout << "### Birks coeffitients for Geant4 materials" << G4endl;
    for(G4int i=0; i<nG4Birks; ++i) {
      G4cout << "   " << g4MatNames[i] << "   " 
             << g4MatData[i]*MeV/mm << " mm/MeV" << G4endl;
    }
  }
}

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void G4EmSaturation::Initialise()
{
  // M.Hirschberg et al., IEEE Trans. Nuc. Sci. 39 (1992) 511
  // SCSN-38 kB = 0.00842 g/cm^2/MeV; rho = 1.06 g/cm^3
  g4MatNames.push_back("G4_POLYSTYRENE");
  g4MatData.push_back(0.07943*mm/MeV);

  // C.Fabjan (private communication)
  // kB = 0.006 g/cm^2/MeV; rho = 7.13 g/cm^3
  g4MatNames.push_back("G4_BGO");
  g4MatData.push_back(0.008415*mm/MeV);

  // A.Ribon analysis of publications
  // Scallettar et al., Phys. Rev. A25 (1982) 2419.
  // NIM A 523 (2004) 275. 
  // kB = 0.022 g/cm^2/MeV; rho = 1.396 g/cm^3; 
  // ATLAS Efield = 10 kV/cm provide the strongest effect 
  g4MatNames.push_back("G4_lAr");
  g4MatData.push_back(0.1576*mm/MeV);

  //G4_BARIUM_FLUORIDE
  //G4_CESIUM_IODIDE
  //G4_GEL_PHOTO_EMULSION
  //G4_PHOTO_EMULSION
  //G4_PLASTIC_SC_VINYLTOLUENE
  //G4_SODIUM_IODIDE
  //G4_STILBENE
  //G4_lAr
  //G4_PbWO4
  //G4_Lucite

  nG4Birks = g4MatData.size();
}

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