G4MuBremsstrahlungModel.cc

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// $Id$
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4MuBremsstrahlungModel
//
// Author:        Vladimir Ivanchenko on base of Laszlo Urban code
//
// Creation date: 24.06.2002
//
// Modifications:
//
// 04-12-02 Change G4DynamicParticle constructor in PostStepDoIt (V.Ivanchenko)
// 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
// 24-01-03 Fix for compounds (V.Ivanchenko)
// 27-01-03 Make models region aware (V.Ivanchenko)
// 13-02-03 Add name (V.Ivanchenko)
// 10-02-04 Add lowestKinEnergy (V.Ivanchenko)
// 08-04-05 Major optimisation of internal interfaces (V.Ivanchenko)
// 03-08-05 Angular correlations according to PRM (V.Ivanchenko)
// 13-02-06 add ComputeCrossSectionPerAtom (mma)
// 21-03-06 Fix problem of initialisation in case when cuts are not defined (VI)
// 07-11-07 Improve sampling of final state (A.Bogdanov)
// 28-02-08 Use precomputed Z^1/3 and Log(A) (V.Ivanchenko)
//
 
//
// Class Description:
//
//
// -------------------------------------------------------------------
//
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#include "G4MuBremsstrahlungModel.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4Gamma.hh"
#include "G4MuonMinus.hh"
#include "G4MuonPlus.hh"
#include "Randomize.hh"
#include "G4Material.hh"
#include "G4Element.hh"
#include "G4ElementVector.hh"
#include "G4ProductionCutsTable.hh"
#include "G4ParticleChangeForLoss.hh"
 
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using namespace std;
 
G4MuBremsstrahlungModel::G4MuBremsstrahlungModel(const G4ParticleDefinition* p,
                                                 const G4String& nam)
  : G4VEmModel(nam),
    particle(0),
    sqrte(sqrt(exp(1.))),
    bh(202.4),
    bh1(446.),
    btf(183.),
    btf1(1429.),
    fParticleChange(0),
    lowestKinEnergy(1.0*GeV),
    minThreshold(1.0*keV)
{
  theGamma = G4Gamma::Gamma();
  nist = G4NistManager::Instance();
 
  mass = rmass = cc = coeff = 1.0;
 
  fDN[0] = 0.0;
  for(G4int i=1; i<93; ++i) {
    G4double dn = 1.54*nist->GetA27(i);
    fDN[i] = dn;
    if(1 < i) {
      fDN[i] /= std::pow(dn, 1./G4double(i));
    }
  }
 
  if(p) { SetParticle(p); }
}
 
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G4MuBremsstrahlungModel::~G4MuBremsstrahlungModel()
{
  size_t n = partialSumSigma.size();
  if(n > 0) {
    for(size_t i=0; i<n; i++) {
      delete partialSumSigma[i];
    }
  }
}
 
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G4double G4MuBremsstrahlungModel::MinEnergyCut(const G4ParticleDefinition*,
                                               const G4MaterialCutsCouple*)
{
  return minThreshold;
}
 
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void G4MuBremsstrahlungModel::Initialise(const G4ParticleDefinition* p,
                                         const G4DataVector& cuts)
{
  if(p) { SetParticle(p); }
 
  // partial cross section is computed for fixed energy
  G4double fixedEnergy = 0.5*HighEnergyLimit();
 
  const G4ProductionCutsTable* theCoupleTable=
        G4ProductionCutsTable::GetProductionCutsTable();
  if(theCoupleTable) {
    G4int numOfCouples = theCoupleTable->GetTableSize();
 
    G4int nn = partialSumSigma.size();
    G4int nc = cuts.size();
 
    // do we need to perform initialisation?
    if(nn == numOfCouples) { return; }
 
    // clear old data    
    if(nn > 0) {
      for (G4int ii=0; ii<nn; ii++){
    G4DataVector* a = partialSumSigma[ii];
    if ( a ) { delete a; }
      } 
      partialSumSigma.clear();
    }
    // fill new data
    if (numOfCouples>0) {
      for (G4int i=0; i<numOfCouples; i++) {
        G4double cute = DBL_MAX;
 
    // protection for usage with extrapolator
        if(i < nc) { cute = cuts[i]; }
 
        const G4MaterialCutsCouple* couple = 
      theCoupleTable->GetMaterialCutsCouple(i);
    const G4Material* material = couple->GetMaterial();
    G4DataVector* dv = ComputePartialSumSigma(material,fixedEnergy,cute);
    partialSumSigma.push_back(dv);
      }
    }
  }
 
  // define pointer to G4ParticleChange
  if(!fParticleChange) { fParticleChange = GetParticleChangeForLoss(); }
}
 
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G4double G4MuBremsstrahlungModel::ComputeDEDXPerVolume(
                          const G4Material* material,
                                              const G4ParticleDefinition*,
                                                    G4double kineticEnergy,
                                                    G4double cutEnergy)
{
  G4double dedx = 0.0;
  if (kineticEnergy <= lowestKinEnergy) return dedx;
 
  G4double tmax = kineticEnergy;
  G4double cut  = std::min(cutEnergy,tmax);
  if(cut < minThreshold) cut = minThreshold;
 
  const G4ElementVector* theElementVector = material->GetElementVector();
  const G4double* theAtomicNumDensityVector =
    material->GetAtomicNumDensityVector();
 
  //  loop for elements in the material
  for (size_t i=0; i<material->GetNumberOfElements(); i++) {
 
    G4double loss = 
      ComputMuBremLoss((*theElementVector)[i]->GetZ(), kineticEnergy, cut);
 
    dedx += loss*theAtomicNumDensityVector[i];
  }
  //  G4cout << "BR e= " << kineticEnergy << "  dedx= " << dedx << G4endl;
  if(dedx < 0.) dedx = 0.;
  return dedx;
}
 
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G4double G4MuBremsstrahlungModel::ComputMuBremLoss(G4double Z,
                                                   G4double tkin, G4double cut)
{
  G4double totalEnergy = mass + tkin;
  G4double ak1 = 0.05;
  G4int    k2=5;
  G4double xgi[]={0.03377,0.16940,0.38069,0.61931,0.83060,0.96623};
  G4double wgi[]={0.08566,0.18038,0.23396,0.23396,0.18038,0.08566};
  G4double loss = 0.;
 
  G4double vcut = cut/totalEnergy;
  G4double vmax = tkin/totalEnergy;
 
  G4double aaa = 0.;
  G4double bbb = vcut;
  if(vcut>vmax) bbb=vmax ;
  G4int kkk = (G4int)((bbb-aaa)/ak1)+k2 ;
  G4double hhh=(bbb-aaa)/float(kkk) ;
 
  G4double aa = aaa;
  for(G4int l=0; l<kkk; l++)
  {
    for(G4int i=0; i<6; i++)
    {
      G4double ep = (aa + xgi[i]*hhh)*totalEnergy;
      loss += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
    }
    aa += hhh;
  }
 
  loss *=hhh*totalEnergy ;
 
  return loss;
}
 
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G4double G4MuBremsstrahlungModel::ComputeMicroscopicCrossSection(
                                           G4double tkin,
                                           G4double Z,
                                           G4double cut)
{
  G4double totalEnergy = tkin + mass;
  G4double ak1 = 2.3;
  G4int    k2  = 4;
  G4double xgi[]={0.03377,0.16940,0.38069,0.61931,0.83060,0.96623};
  G4double wgi[]={0.08566,0.18038,0.23396,0.23396,0.18038,0.08566};
  G4double cross = 0.;
 
  if(cut >= tkin) return cross;
 
  G4double vcut = cut/totalEnergy;
  G4double vmax = tkin/totalEnergy;
 
  G4double aaa = log(vcut);
  G4double bbb = log(vmax);
  G4int    kkk = (G4int)((bbb-aaa)/ak1)+k2 ;
  G4double hhh = (bbb-aaa)/G4double(kkk);
 
  G4double aa = aaa;
 
  for(G4int l=0; l<kkk; l++)
  {
    for(G4int i=0; i<6; i++)
    {
      G4double ep = exp(aa + xgi[i]*hhh)*totalEnergy;
      cross += ep*wgi[i]*ComputeDMicroscopicCrossSection(tkin, Z, ep);
    }
    aa += hhh;
  }
 
  cross *=hhh;
 
  //G4cout << "BR e= " << tkin<< "  cross= " << cross/barn << G4endl;
 
  return cross;
}
 
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G4double G4MuBremsstrahlungModel::ComputeDMicroscopicCrossSection(
                                           G4double tkin,
                                           G4double Z,
                                           G4double gammaEnergy)
//  differential cross section
{
  G4double dxsection = 0.;
 
  if( gammaEnergy > tkin) return dxsection ;
 
  G4double E = tkin + mass ;
  G4double v = gammaEnergy/E ;
  G4double delta = 0.5*mass*mass*v/(E-gammaEnergy) ;
  G4double rab0=delta*sqrte ;
 
  G4int iz = G4int(Z);
  if(iz < 1) iz = 1;
  else if(iz > 92) iz = 92;
 
  G4double z13 = 1.0/nist->GetZ13(iz);
  G4double dnstar = fDN[iz];
 
  G4double b,b1;
 
  if(1 == iz) {
    b  = bh;
    b1 = bh1;
  } else {
    b  = btf;
    b1 = btf1;
  }
 
  // nucleus contribution logarithm
  G4double rab1=b*z13;
  G4double fn=log(rab1/(dnstar*(electron_mass_c2+rab0*rab1))*
              (mass+delta*(dnstar*sqrte-2.))) ;
  if(fn <0.) fn = 0. ;
  // electron contribution logarithm
  G4double epmax1=E/(1.+0.5*mass*rmass/E) ;
  G4double fe=0.;
  if(gammaEnergy<epmax1)
  {
    G4double rab2=b1*z13*z13 ;
    fe=log(rab2*mass/((1.+delta*rmass/(electron_mass_c2*sqrte))*
                              (electron_mass_c2+rab0*rab2))) ;
    if(fe<0.) fe=0. ;
  }
 
  dxsection = coeff*(1.-v*(1. - 0.75*v))*Z*(fn*Z + fe)/gammaEnergy;
 
  return dxsection;
}
 
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G4double G4MuBremsstrahlungModel::ComputeCrossSectionPerAtom(
                                           const G4ParticleDefinition*,
                                                 G4double kineticEnergy,
                         G4double Z, G4double,
                                                 G4double cutEnergy,
                                                 G4double maxEnergy)
{
  G4double cross = 0.0;
  if (kineticEnergy <= lowestKinEnergy) return cross;
  G4double tmax = std::min(maxEnergy, kineticEnergy);
  G4double cut  = std::min(cutEnergy, kineticEnergy);
  if(cut < minThreshold) cut = minThreshold;
  if (cut >= tmax) return cross;
 
  cross = ComputeMicroscopicCrossSection (kineticEnergy, Z, cut);
  if(tmax < kineticEnergy) {
    cross -= ComputeMicroscopicCrossSection(kineticEnergy, Z, tmax);
  }
  return cross;
}
 
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G4DataVector* G4MuBremsstrahlungModel::ComputePartialSumSigma(
                                       const G4Material* material,
                       G4double kineticEnergy,
                       G4double cut)
 
// Build the table of cross section per element. 
// The table is built for material 
// This table is used to select randomly an element in the material.
{
  G4int nElements = material->GetNumberOfElements();
  const G4ElementVector* theElementVector = material->GetElementVector();
  const G4double* theAtomNumDensityVector = 
    material->GetAtomicNumDensityVector();
 
  G4DataVector* dv = new G4DataVector();
 
  G4double cross = 0.0;
 
  for (G4int i=0; i<nElements; i++ ) {
    cross += theAtomNumDensityVector[i] 
      * ComputeMicroscopicCrossSection(kineticEnergy, 
                       (*theElementVector)[i]->GetZ(), cut);
    dv->push_back(cross);
  }
  return dv;
}
 
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void G4MuBremsstrahlungModel::SampleSecondaries(
                              std::vector<G4DynamicParticle*>* vdp,
                  const G4MaterialCutsCouple* couple,
                  const G4DynamicParticle* dp,
                  G4double minEnergy,
                  G4double maxEnergy)
{
  G4double kineticEnergy = dp->GetKineticEnergy();
  // check against insufficient energy
  G4double tmax = std::min(kineticEnergy, maxEnergy);
  G4double tmin = std::min(kineticEnergy, minEnergy);
  if(tmin < minThreshold) tmin = minThreshold;
  if(tmin >= tmax) return;
 
  // ===== sampling of energy transfer ======
 
  G4ParticleMomentum partDirection = dp->GetMomentumDirection();
 
  // select randomly one element constituing the material
  const G4Element* anElement = SelectRandomAtom(couple);
  G4double Z = anElement->GetZ();
 
  G4double totalEnergy   = kineticEnergy + mass;
  G4double totalMomentum = sqrt(kineticEnergy*(kineticEnergy + 2.0*mass));
 
  G4double func1 = tmin*
    ComputeDMicroscopicCrossSection(kineticEnergy,Z,tmin);
 
  G4double lnepksi, epksi;
  G4double func2;
 
  G4double xmin = log(tmin/MeV);
  G4double xmax = log(kineticEnergy/tmin);
 
  do {
    lnepksi = xmin + G4UniformRand()*xmax;
    epksi   = MeV*exp(lnepksi);
    func2   = epksi*ComputeDMicroscopicCrossSection(kineticEnergy,Z,epksi);
 
  } while(func2 < func1*G4UniformRand());
 
  G4double gEnergy = epksi;
 
  // ===== sample angle =====
 
  G4double gam  = totalEnergy/mass;
  G4double rmax = gam*std::min(1.0, totalEnergy/gEnergy - 1.0);
  G4double rmax2= rmax*rmax;
  G4double x = G4UniformRand()*rmax2/(1.0 + rmax2);
 
  G4double theta = sqrt(x/(1.0 - x))/gam;
  G4double sint  = sin(theta);
  G4double phi   = twopi * G4UniformRand() ;
  G4double dirx  = sint*cos(phi), diry = sint*sin(phi), dirz = cos(theta) ;
 
  G4ThreeVector gDirection(dirx, diry, dirz);
  gDirection.rotateUz(partDirection);
 
  partDirection *= totalMomentum;
  partDirection -= gEnergy*gDirection;
  partDirection = partDirection.unit();
 
  // primary change
  kineticEnergy -= gEnergy;
  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
  fParticleChange->SetProposedMomentumDirection(partDirection);
 
  // save secondary
  G4DynamicParticle* aGamma = 
    new G4DynamicParticle(theGamma,gDirection,gEnergy);
  vdp->push_back(aGamma);
}
 
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const G4Element* G4MuBremsstrahlungModel::SelectRandomAtom(
           const G4MaterialCutsCouple* couple) const
{
  // select randomly 1 element within the material
 
  const G4Material* material = couple->GetMaterial();
  G4int nElements = material->GetNumberOfElements();
  const G4ElementVector* theElementVector = material->GetElementVector();
  if(1 == nElements) { return (*theElementVector)[0]; }
  else if(1 > nElements) { return 0; }
 
  G4DataVector* dv = partialSumSigma[couple->GetIndex()];
  G4double rval = G4UniformRand()*((*dv)[nElements-1]);
  for (G4int i=0; i<nElements; i++) {
    if (rval <= (*dv)[i]) { return (*theElementVector)[i]; }
  }
  return (*theElementVector)[nElements-1];
}
 
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......