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geant4/source/processes/electromagnetic/standard/src/G4eBremsstrahlungModel.cc
T
Gabriele Cosmo 89a9605df1 Import Geant4 9.4.0 source tree
2016-06-09 16:25:56 +02:00

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//
// ********************************************************************
// * License and Disclaimer *
// * *
// * The Geant4 software is copyright of the Copyright Holders of *
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// * regarding this software system or assume any liability for its *
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// * *
// * This code implementation is the result of the scientific and *
// * technical work of the GEANT4 collaboration. *
// * By using, copying, modifying or distributing the software (or *
// * any work based on the software) you agree to acknowledge its *
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// ********************************************************************
//
// $Id: G4eBremsstrahlungModel.cc,v 1.48 2010/10/26 10:35:22 vnivanch Exp $
// GEANT4 tag $Name: geant4-09-04 $
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name: G4eBremsstrahlungModel
//
// Author: Vladimir Ivanchenko on base of Laszlo Urban code
//
// Creation date: 03.01.2002
//
// Modifications:
//
// 11-11-02 Fix division by 0 (V.Ivanchenko)
// 04-12-02 Change G4DynamicParticle constructor in PostStep (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)
// 09-05-03 Fix problem of supression function + optimise sampling (V.Ivanchenko)
// 20-05-04 Correction to ensure unit independence (L.Urban)
// 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
// 03-08-05 Add extra protection at initialisation (V.Ivantchenko)
// 07-02-06 public function ComputeCrossSectionPerAtom() (mma)
// 21-03-06 Fix problem of initialisation in case when cuts are not defined (VI)
// 27-03-06 Fix calculation of fl parameter at low energy (energy loss) (VI)
// 15-02-07 correct LPMconstant by a factor 2, thanks to G. Depaola (mma)
// 09-09-08 MigdalConstant increased in (2pi)^2 times (A.Schaelicke)
// 13-10-10 Add angular distributon interface (VI)
//
// Class Description:
//
//
// -------------------------------------------------------------------
//
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
#include "G4eBremsstrahlungModel.hh"
#include "G4Electron.hh"
#include "G4Positron.hh"
#include "G4Gamma.hh"
#include "Randomize.hh"
#include "G4Material.hh"
#include "G4Element.hh"
#include "G4ElementVector.hh"
#include "G4ProductionCutsTable.hh"
#include "G4DataVector.hh"
#include "G4ParticleChangeForLoss.hh"
#include "G4ModifiedTsai.hh"
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
using namespace std;
G4eBremsstrahlungModel::G4eBremsstrahlungModel(const G4ParticleDefinition* p,
const G4String& nam)
: G4VEmModel(nam),
particle(0),
isElectron(true),
probsup(1.0),
MigdalConstant(classic_electr_radius*electron_Compton_length*electron_Compton_length*4.0*pi),
LPMconstant(fine_structure_const*electron_mass_c2*electron_mass_c2/(4.*pi*hbarc)),
isInitialised(false)
{
if(p) { SetParticle(p); }
theGamma = G4Gamma::Gamma();
minThreshold = 0.1*keV;
SetAngularDistribution(new G4ModifiedTsai());
highKinEnergy = HighEnergyLimit();
lowKinEnergy = LowEnergyLimit();
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4eBremsstrahlungModel::~G4eBremsstrahlungModel()
{
size_t n = partialSumSigma.size();
if(n > 0) {
for(size_t i=0; i<n; i++) {
delete partialSumSigma[i];
}
}
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
void G4eBremsstrahlungModel::SetParticle(const G4ParticleDefinition* p)
{
particle = p;
if(p == G4Electron::Electron()) isElectron = true;
else isElectron = false;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4eBremsstrahlungModel::MinEnergyCut(const G4ParticleDefinition*,
const G4MaterialCutsCouple*)
{
return minThreshold;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
void G4eBremsstrahlungModel::Initialise(const G4ParticleDefinition* p,
const G4DataVector& cuts)
{
if(p) { SetParticle(p); }
highKinEnergy = HighEnergyLimit();
lowKinEnergy = LowEnergyLimit();
const G4ProductionCutsTable* theCoupleTable=
G4ProductionCutsTable::GetProductionCutsTable();
if(theCoupleTable) {
G4int numOfCouples = theCoupleTable->GetTableSize();
G4int nn = partialSumSigma.size();
G4int nc = cuts.size();
if(nn > 0) {
for (G4int ii=0; ii<nn; ii++){
G4DataVector* a=partialSumSigma[ii];
if ( a ) delete a;
}
partialSumSigma.clear();
}
if(numOfCouples>0) {
for (G4int i=0; i<numOfCouples; i++) {
G4double cute = DBL_MAX;
if(i < nc) cute = cuts[i];
const G4MaterialCutsCouple* couple = theCoupleTable->GetMaterialCutsCouple(i);
const G4Material* material = couple->GetMaterial();
G4DataVector* dv = ComputePartialSumSigma(material, 0.5*highKinEnergy,
std::min(cute, 0.25*highKinEnergy));
partialSumSigma.push_back(dv);
}
}
}
if(isInitialised) return;
fParticleChange = GetParticleChangeForLoss();
isInitialised = true;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4eBremsstrahlungModel::ComputeDEDXPerVolume(
const G4Material* material,
const G4ParticleDefinition* p,
G4double kineticEnergy,
G4double cutEnergy)
{
if(!particle) { SetParticle(p); }
if(kineticEnergy < lowKinEnergy) { return 0.0; }
const G4double thigh = 100.*GeV;
G4double cut = std::min(cutEnergy, kineticEnergy);
G4double rate, loss;
const G4double factorHigh = 36./(1450.*GeV);
const G4double coef1 = -0.5;
const G4double coef2 = 2./9.;
const G4ElementVector* theElementVector = material->GetElementVector();
const G4double* theAtomicNumDensityVector = material->GetAtomicNumDensityVector();
G4double totalEnergy = kineticEnergy + electron_mass_c2;
G4double dedx = 0.0;
// loop for elements in the material
for (size_t i=0; i<material->GetNumberOfElements(); i++) {
G4double Z = (*theElementVector)[i]->GetZ();
G4double natom = theAtomicNumDensityVector[i];
// loss for MinKinEnergy<KineticEnergy<=100 GeV
if (kineticEnergy <= thigh) {
// x = log(totalEnergy/electron_mass_c2);
loss = ComputeBremLoss(Z, kineticEnergy, cut) ;
if (!isElectron) loss *= PositronCorrFactorLoss(Z, kineticEnergy, cut);
// extrapolation for KineticEnergy>100 GeV
} else {
// G4double xhigh = log(thigh/electron_mass_c2);
G4double cuthigh = thigh*0.5;
if (cut < thigh) {
loss = ComputeBremLoss(Z, thigh, cut) ;
if (!isElectron) loss *= PositronCorrFactorLoss(Z, thigh, cut) ;
rate = cut/totalEnergy;
loss *= (1. + coef1*rate + coef2*rate*rate);
rate = cut/thigh;
loss /= (1.+coef1*rate+coef2*rate*rate);
} else {
loss = ComputeBremLoss(Z, thigh, cuthigh) ;
if (!isElectron) loss *= PositronCorrFactorLoss(Z, thigh, cuthigh) ;
rate = cut/totalEnergy;
loss *= (1. + coef1*rate + coef2*rate*rate);
loss *= cut*factorHigh;
}
}
loss *= natom;
G4double kp2 = MigdalConstant*totalEnergy*totalEnergy
* (material->GetElectronDensity()) ;
// now compute the correction due to the supression(s)
G4double kmin = 1.*eV;
G4double kmax = cut;
if (kmax > kmin) {
G4double floss = 0.;
G4int nmax = 100;
G4double vmin=log(kmin);
G4double vmax=log(kmax) ;
G4int nn = (G4int)(nmax*(vmax-vmin)/(log(highKinEnergy)-vmin)) ;
G4double u,fac,c,v,dv ;
if(nn > 0) {
dv = (vmax-vmin)/nn ;
v = vmin-dv ;
for(G4int n=0; n<=nn; n++) {
v += dv;
u = exp(v);
fac = u*SupressionFunction(material,kineticEnergy,u);
fac *= probsup*(u*u/(u*u+kp2))+1.-probsup;
if ((n==0)||(n==nn)) c=0.5;
else c=1. ;
fac *= c ;
floss += fac ;
}
floss *=dv/(kmax-kmin);
} else {
floss = 1.;
}
if(floss > 1.) floss = 1.;
// correct the loss
loss *= floss;
}
dedx += loss;
}
if(dedx < 0.) { dedx = 0.; }
return dedx;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4eBremsstrahlungModel::ComputeBremLoss(G4double Z, G4double T,
G4double Cut)
// compute loss due to soft brems
{
static const G4double beta=1.0, ksi=2.0;
static const G4double clossh = 0.254 , closslow = 1./3. , alosslow = 1. ;
static const G4double Tlim= 10.*MeV ;
static const G4double xlim = 1.2 ;
static const G4int NZ = 8 ;
static const G4int Nloss = 11 ;
static const G4double ZZ[NZ] =
{2.,4.,6.,14.,26.,50.,82.,92.};
static const G4double coefloss[NZ][Nloss] = {
// Z=2
{ 0.98916, 0.47564, -0.2505, -0.45186, 0.14462,
0.21307, -0.013738, -0.045689, -0.0042914, 0.0034429,
0.00064189},
// Z=4
{ 1.0626, 0.37662, -0.23646, -0.45188, 0.14295,
0.22906, -0.011041, -0.051398, -0.0055123, 0.0039919,
0.00078003},
// Z=6
{ 1.0954, 0.315, -0.24011, -0.43849, 0.15017,
0.23001, -0.012846, -0.052555, -0.0055114, 0.0041283,
0.00080318},
// Z=14
{ 1.1649, 0.18976, -0.24972, -0.30124, 0.1555,
0.13565, -0.024765, -0.027047, -0.00059821, 0.0019373,
0.00027647},
// Z=26
{ 1.2261, 0.14272, -0.25672, -0.28407, 0.13874,
0.13586, -0.020562, -0.026722, -0.00089557, 0.0018665,
0.00026981},
// Z=50
{ 1.3147, 0.020049, -0.35543, -0.13927, 0.17666,
0.073746, -0.036076, -0.013407, 0.0025727, 0.00084005,
-1.4082e-05},
// Z=82
{ 1.3986, -0.10586, -0.49187, -0.0048846, 0.23621,
0.031652, -0.052938, -0.0076639, 0.0048181, 0.00056486,
-0.00011995},
// Z=92
{ 1.4217, -0.116, -0.55497, -0.044075, 0.27506,
0.081364, -0.058143, -0.023402, 0.0031322, 0.0020201,
0.00017519}
} ;
static G4double aaa = 0.414;
static G4double bbb = 0.345;
static G4double ccc = 0.460;
G4int iz = 0;
G4double delz = 1.e6;
for (G4int ii=0; ii<NZ; ii++)
{
G4double dz = std::abs(Z-ZZ[ii]);
if(dz < delz) {
iz = ii;
delz = dz;
}
}
G4double xx = log10(T/MeV);
G4double fl = 1.;
if (xx <= xlim)
{
xx /= xlim;
G4double yy = 1.0;
fl = 0.0;
for (G4int j=0; j<Nloss; j++) {
fl += yy+coefloss[iz][j];
yy *= xx;
}
if (fl < 0.00001) fl = 0.00001;
else if (fl > 1.0) fl = 1.0;
}
G4double loss;
G4double E = T+electron_mass_c2 ;
loss = Z*(Z+ksi)*E*E/(T+E)*exp(beta*log(Cut/T))*(2.-clossh*exp(log(Z)/4.));
if (T <= Tlim) loss /= exp(closslow*log(Tlim/T));
if( T <= Cut) loss *= exp(alosslow*log(T/Cut));
// correction
loss *= (aaa+bbb*T/Tlim)/(1.+ccc*T/Tlim);
loss *= fl;
loss /= Avogadro;
return loss;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4eBremsstrahlungModel::PositronCorrFactorLoss(G4double Z,
G4double kineticEnergy, G4double cut)
//calculates the correction factor for the energy loss due to bremsstrahlung for positrons
//the same correction is in the (discrete) bremsstrahlung
{
static const G4double K = 132.9416*eV ;
static const G4double a1=4.15e-1, a3=2.10e-3, a5=54.0e-5 ;
G4double x = log(kineticEnergy/(K*Z*Z)), x2 = x*x, x3 = x2*x;
G4double eta = 0.5+atan(a1*x+a3*x3+a5*x3*x2)/pi;
G4double e0 = cut/kineticEnergy;
G4double factor = 0.0;
if (e0 < 1.0) {
factor=log(1.-e0)/eta;
factor=exp(factor);
}
factor = eta*(1.-factor)/e0;
return factor;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4eBremsstrahlungModel::CrossSectionPerVolume(
const G4Material* material,
const G4ParticleDefinition* p,
G4double kineticEnergy,
G4double cutEnergy,
G4double maxEnergy)
{
if(!particle) { SetParticle(p); }
G4double cross = 0.0;
G4double tmax = min(maxEnergy, kineticEnergy);
G4double cut = max(cutEnergy, minThreshold);
if(cut >= tmax) { return cross; }
const G4ElementVector* theElementVector = material->GetElementVector();
const G4double* theAtomNumDensityVector = material->GetAtomicNumDensityVector();
G4double dum=0.;
for (size_t i=0; i<material->GetNumberOfElements(); i++) {
cross += theAtomNumDensityVector[i] * ComputeCrossSectionPerAtom(p,
kineticEnergy, (*theElementVector)[i]->GetZ(), dum, cut);
if (tmax < kineticEnergy) {
cross -= theAtomNumDensityVector[i] * ComputeCrossSectionPerAtom(p,
kineticEnergy, (*theElementVector)[i]->GetZ(), dum, tmax);
}
}
// now compute the correction due to the supression(s)
G4double kmax = tmax;
G4double kmin = cut;
G4double totalEnergy = kineticEnergy+electron_mass_c2 ;
G4double kp2 = MigdalConstant*totalEnergy*totalEnergy
*(material->GetElectronDensity());
G4double fsig = 0.;
G4int nmax = 100;
G4double vmin=log(kmin);
G4double vmax=log(kmax) ;
G4int nn = (G4int)(nmax*(vmax-vmin)/(log(highKinEnergy)-vmin));
G4double u,fac,c,v,dv,y ;
if(nn > 0) {
dv = (vmax-vmin)/nn ;
v = vmin-dv ;
for(G4int n=0; n<=nn; n++) {
v += dv;
u = exp(v);
fac = SupressionFunction(material, kineticEnergy, u);
y = u/kmax;
fac *= (4.-4.*y+3.*y*y)/3.;
fac *= probsup*(u*u/(u*u+kp2))+1.-probsup;
if ((n==0)||(n==nn)) c=0.5;
else c=1. ;
fac *= c;
fsig += fac;
}
y = kmin/kmax ;
fsig *=dv/(-4.*log(y)/3.-4.*(1.-y)/3.+0.5*(1.-y*y));
} else {
fsig = 1.;
}
if (fsig > 1.) fsig = 1.;
// correct the cross section
cross *= fsig;
return cross;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4eBremsstrahlungModel::ComputeCrossSectionPerAtom(
const G4ParticleDefinition*,
G4double kineticEnergy,
G4double Z, G4double,
G4double cut, G4double)
// Calculates the cross section per atom in GEANT4 internal units.
//
{
G4double cross = 0.0 ;
if ( kineticEnergy < 1*keV || kineticEnergy < cut) { return cross; }
static const G4double ksi=2.0, alfa=1.00;
static const G4double csigh = 0.127, csiglow = 0.25, asiglow = 0.020*MeV ;
static const G4double Tlim = 10.*MeV ;
static const G4double xlim = 1.2 ;
static const G4int NZ = 8 ;
static const G4int Nsig = 11 ;
static const G4double ZZ[NZ] =
{2.,4.,6.,14.,26.,50.,82.,92.} ;
static const G4double coefsig[NZ][Nsig] = {
// Z=2
{ 0.4638, 0.37748, 0.32249, -0.060362, -0.065004,
-0.033457, -0.004583, 0.011954, 0.0030404, -0.0010077,
-0.00028131},
// Z=4
{ 0.50008, 0.33483, 0.34364, -0.086262, -0.055361,
-0.028168, -0.0056172, 0.011129, 0.0027528, -0.00092265,
-0.00024348},
// Z=6
{ 0.51587, 0.31095, 0.34996, -0.11623, -0.056167,
-0.0087154, 0.00053943, 0.0054092, 0.00077685, -0.00039635,
-6.7818e-05},
// Z=14
{ 0.55058, 0.25629, 0.35854, -0.080656, -0.054308,
-0.049933, -0.00064246, 0.016597, 0.0021789, -0.001327,
-0.00025983},
// Z=26
{ 0.5791, 0.26152, 0.38953, -0.17104, -0.099172,
0.024596, 0.023718, -0.0039205, -0.0036658, 0.00041749,
0.00023408},
// Z=50
{ 0.62085, 0.27045, 0.39073, -0.37916, -0.18878,
0.23905, 0.095028, -0.068744, -0.023809, 0.0062408,
0.0020407},
// Z=82
{ 0.66053, 0.24513, 0.35404, -0.47275, -0.22837,
0.35647, 0.13203, -0.1049, -0.034851, 0.0095046,
0.0030535},
// Z=92
{ 0.67143, 0.23079, 0.32256, -0.46248, -0.20013,
0.3506, 0.11779, -0.1024, -0.032013, 0.0092279,
0.0028592}
} ;
G4int iz = 0 ;
G4double delz = 1.e6 ;
for (G4int ii=0; ii<NZ; ii++)
{
G4double absdelz = std::abs(Z-ZZ[ii]);
if(absdelz < delz)
{
iz = ii ;
delz = absdelz;
}
}
G4double xx = log10(kineticEnergy/MeV) ;
G4double fs = 1. ;
if (xx <= xlim) {
fs = coefsig[iz][Nsig-1] ;
for (G4int j=Nsig-2; j>=0; j--) {
fs = fs*xx+coefsig[iz][j] ;
}
if(fs < 0.) fs = 0.;
}
cross = Z*(Z+ksi)*(1.-csigh*exp(log(Z)/4.))*pow(log(kineticEnergy/cut),alfa);
if (kineticEnergy <= Tlim)
cross *= exp(csiglow*log(Tlim/kineticEnergy))
*(1.+asiglow/(sqrt(Z)*kineticEnergy));
if (!isElectron)
cross *= PositronCorrFactorSigma(Z, kineticEnergy, cut);
cross *= fs/Avogadro ;
if (cross < 0.) cross = 0.;
return cross;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4eBremsstrahlungModel::PositronCorrFactorSigma( G4double Z,
G4double kineticEnergy, G4double cut)
//Calculates the correction factor for the total cross section of the positron
// bremsstrahl.
// Eta is the ratio of positron to electron energy loss by bremstrahlung.
// A parametrized formula from L. Urban is used to estimate eta. It is a fit to
// the results of L. Kim & al: Phys Rev. A33,3002 (1986)
{
static const G4double K = 132.9416*eV;
static const G4double a1 = 4.15e-1, a3 = 2.10e-3, a5 = 54.0e-5;
G4double x = log(kineticEnergy/(K*Z*Z));
G4double x2 = x*x;
G4double x3 = x2*x;
G4double eta = 0.5 + atan(a1*x + a3*x3 + a5*x3*x2)/pi ;
G4double alfa = (1. - eta)/eta;
return eta*pow((1. - cut/kineticEnergy), alfa);
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4DataVector* G4eBremsstrahlungModel::ComputePartialSumSigma(
const G4Material* material,
G4double kineticEnergy,
G4double cut)
// Build the table of cross section per element.
//The table is built for MATERIALS.
// This table is used by DoIt to select randomly an element in the material.
{
G4int nElements = material->GetNumberOfElements();
const G4ElementVector* theElementVector = material->GetElementVector();
const G4double* theAtomNumDensityVector = material->GetAtomicNumDensityVector();
G4double dum = 0.;
G4DataVector* dv = new G4DataVector();
G4double cross = 0.0;
for (G4int i=0; i<nElements; i++ ) {
cross += theAtomNumDensityVector[i] * ComputeCrossSectionPerAtom( particle,
kineticEnergy, (*theElementVector)[i]->GetZ(), dum, cut);
dv->push_back(cross);
}
return dv;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
void G4eBremsstrahlungModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
const G4MaterialCutsCouple* couple,
const G4DynamicParticle* dp,
G4double tmin,
G4double maxEnergy)
// The emitted gamma energy is sampled using a parametrized formula
// from L. Urban.
// This parametrization is derived from :
// cross-section values of Seltzer and Berger for electron energies
// 1 keV - 10 GeV,
// screened Bethe Heilter differential cross section above 10 GeV,
// Migdal corrections in both case.
// Seltzer & Berger: Nim B 12:95 (1985)
// Nelson, Hirayama & Rogers: Technical report 265 SLAC (1985)
// Migdal: Phys Rev 103:1811 (1956); Messel & Crawford: Pergamon Press (1970)
//
// A modified version of the random number techniques of Butcher&Messel is used
// (Nuc Phys 20(1960),15).
{
G4double kineticEnergy = dp->GetKineticEnergy();
G4double tmax = min(maxEnergy, kineticEnergy);
if(tmin >= tmax) { return; }
//
// GEANT4 internal units.
//
static const G4double
ah10 = 4.67733E+00, ah11 =-6.19012E-01, ah12 = 2.02225E-02,
ah20 =-7.34101E+00, ah21 = 1.00462E+00, ah22 =-3.20985E-02,
ah30 = 2.93119E+00, ah31 =-4.03761E-01, ah32 = 1.25153E-02;
static const G4double
bh10 = 4.23071E+00, bh11 =-6.10995E-01, bh12 = 1.95531E-02,
bh20 =-7.12527E+00, bh21 = 9.69160E-01, bh22 =-2.74255E-02,
bh30 = 2.69925E+00, bh31 =-3.63283E-01, bh32 = 9.55316E-03;
static const G4double
al00 =-2.05398E+00, al01 = 2.38815E-02, al02 = 5.25483E-04,
al10 =-7.69748E-02, al11 =-6.91499E-02, al12 = 2.22453E-03,
al20 = 4.06463E-02, al21 =-1.01281E-02, al22 = 3.40919E-04;
static const G4double
bl00 = 1.04133E+00, bl01 =-9.43291E-03, bl02 =-4.54758E-04,
bl10 = 1.19253E-01, bl11 = 4.07467E-02, bl12 =-1.30718E-03,
bl20 =-1.59391E-02, bl21 = 7.27752E-03, bl22 =-1.94405E-04;
static const G4double tlow = 1.*MeV;
G4double gammaEnergy;
G4bool LPMOK = false;
const G4Material* material = couple->GetMaterial();
// select randomly one element constituing the material
const G4Element* anElement = SelectRandomAtom(couple);
// Extract Z factors for this Element
G4double lnZ = 3.*(anElement->GetIonisation()->GetlogZ3());
G4double FZ = lnZ* (4.- 0.55*lnZ);
G4double ZZ = anElement->GetIonisation()->GetZZ3();
// limits of the energy sampling
G4double totalEnergy = kineticEnergy + electron_mass_c2;
G4ThreeVector direction = dp->GetMomentumDirection();
G4double xmin = tmin/kineticEnergy;
G4double xmax = tmax/kineticEnergy;
G4double kappa = 0.0;
if(xmax >= 1.) { xmax = 1.; }
else { kappa = log(xmax)/log(xmin); }
G4double epsilmin = tmin/totalEnergy;
G4double epsilmax = tmax/totalEnergy;
// Migdal factor
G4double MigdalFactor = (material->GetElectronDensity())*MigdalConstant
/ (epsilmax*epsilmax);
G4double x, epsil, greject, migdal, grejmax, q;
G4double U = log(kineticEnergy/electron_mass_c2);
G4double U2 = U*U;
// precalculated parameters
G4double ah, bh;
G4double screenfac = 0.0;
if (kineticEnergy > tlow) {
G4double ah1 = ah10 + ZZ* (ah11 + ZZ* ah12);
G4double ah2 = ah20 + ZZ* (ah21 + ZZ* ah22);
G4double ah3 = ah30 + ZZ* (ah31 + ZZ* ah32);
G4double bh1 = bh10 + ZZ* (bh11 + ZZ* bh12);
G4double bh2 = bh20 + ZZ* (bh21 + ZZ* bh22);
G4double bh3 = bh30 + ZZ* (bh31 + ZZ* bh32);
ah = 1. + (ah1*U2 + ah2*U + ah3) / (U2*U);
bh = 0.75 + (bh1*U2 + bh2*U + bh3) / (U2*U);
// limit of the screening variable
screenfac =
136.*electron_mass_c2/((anElement->GetIonisation()->GetZ3())*totalEnergy);
G4double screenmin = screenfac*epsilmin/(1.-epsilmin);
// Compute the maximum of the rejection function
G4double F1 = max(ScreenFunction1(screenmin) - FZ ,0.);
G4double F2 = max(ScreenFunction2(screenmin) - FZ ,0.);
grejmax = (F1 - epsilmin* (F1*ah - bh*epsilmin*F2))/(42.392 - FZ);
} else {
G4double al0 = al00 + ZZ* (al01 + ZZ* al02);
G4double al1 = al10 + ZZ* (al11 + ZZ* al12);
G4double al2 = al20 + ZZ* (al21 + ZZ* al22);
G4double bl0 = bl00 + ZZ* (bl01 + ZZ* bl02);
G4double bl1 = bl10 + ZZ* (bl11 + ZZ* bl12);
G4double bl2 = bl20 + ZZ* (bl21 + ZZ* bl22);
ah = al0 + al1*U + al2*U2;
bh = bl0 + bl1*U + bl2*U2;
// Compute the maximum of the rejection function
grejmax = max(1. + xmin* (ah + bh*xmin), 1.+ah+bh);
G4double xm = -ah/(2.*bh);
if ( xmin < xm && xm < xmax) grejmax = max(grejmax, 1.+ xm* (ah + bh*xm));
}
//
// sample the energy rate of the emitted gamma for e- kin energy > 1 MeV
//
do {
if (kineticEnergy > tlow) {
do {
q = G4UniformRand();
x = pow(xmin, q + kappa*(1.0 - q));
epsil = x*kineticEnergy/totalEnergy;
G4double screenvar = screenfac*epsil/(1.0-epsil);
G4double F1 = max(ScreenFunction1(screenvar) - FZ ,0.);
G4double F2 = max(ScreenFunction2(screenvar) - FZ ,0.);
migdal = (1. + MigdalFactor)/(1. + MigdalFactor/(x*x));
greject = migdal*(F1 - epsil* (ah*F1 - bh*epsil*F2))/(42.392 - FZ);
/*
if ( greject > grejmax ) {
G4cout << "### G4eBremsstrahlungModel Warning: Majoranta exceeded! "
<< greject << " > " << grejmax
<< " x= " << x
<< " e= " << kineticEnergy
<< G4endl;
}
*/
} while( greject < G4UniformRand()*grejmax );
} else {
do {
q = G4UniformRand();
x = pow(xmin, q + kappa*(1.0 - q));
migdal = (1. + MigdalFactor)/(1. + MigdalFactor/(x*x));
greject = migdal*(1. + x* (ah + bh*x));
/*
if ( greject > grejmax ) {
G4cout << "### G4eBremsstrahlungModel Warning: Majoranta exceeded! "
<< greject << " > " << grejmax
<< " x= " << x
<< " e= " << kineticEnergy
<< G4endl;
}
*/
} while( greject < G4UniformRand()*grejmax );
}
gammaEnergy = x*kineticEnergy;
if (LPMFlag()) {
// take into account the supression due to the LPM effect
if (G4UniformRand() <= SupressionFunction(material,kineticEnergy,
gammaEnergy))
LPMOK = true;
}
else LPMOK = true;
} while (!LPMOK);
//
// angles of the emitted gamma. ( Z - axis along the parent particle)
// use general interface
//
G4double theta = GetAngularDistribution()->PolarAngle(totalEnergy,
totalEnergy-gammaEnergy,
(G4int)anElement->GetZ());
G4double sint = sin(theta);
G4double phi = twopi * G4UniformRand() ;
G4ThreeVector gammaDirection(sint*cos(phi),sint*sin(phi), cos(theta));
gammaDirection.rotateUz(direction);
// create G4DynamicParticle object for the Gamma
G4DynamicParticle* g = new G4DynamicParticle(theGamma,gammaDirection,
gammaEnergy);
vdp->push_back(g);
G4double totMomentum = sqrt(kineticEnergy*(totalEnergy + electron_mass_c2));
G4ThreeVector dir = totMomentum*direction - gammaEnergy*gammaDirection;
direction = dir.unit();
// energy of primary
G4double finalE = kineticEnergy - gammaEnergy;
// stop tracking and create new secondary instead of primary
if(gammaEnergy > SecondaryThreshold()) {
fParticleChange->ProposeTrackStatus(fStopAndKill);
fParticleChange->SetProposedKineticEnergy(0.0);
G4DynamicParticle* el =
new G4DynamicParticle(const_cast<G4ParticleDefinition*>(particle),
direction, finalE);
vdp->push_back(el);
// continue tracking
} else {
fParticleChange->SetProposedMomentumDirection(direction);
fParticleChange->SetProposedKineticEnergy(finalE);
}
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
const G4Element* G4eBremsstrahlungModel::SelectRandomAtom(
const G4MaterialCutsCouple* couple)
{
// select randomly 1 element within the material
const G4Material* material = couple->GetMaterial();
G4int nElements = material->GetNumberOfElements();
const G4ElementVector* theElementVector = material->GetElementVector();
const G4Element* elm = 0;
if(1 < nElements) {
--nElements;
G4DataVector* dv = partialSumSigma[couple->GetIndex()];
G4double rval = G4UniformRand()*((*dv)[nElements]);
elm = (*theElementVector)[nElements];
for (G4int i=0; i<nElements; ++i) {
if (rval <= (*dv)[i]) {
elm = (*theElementVector)[i];
break;
}
}
} else { elm = (*theElementVector)[0]; }
SetCurrentElement(elm);
return elm;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
G4double G4eBremsstrahlungModel::SupressionFunction(const G4Material* material,
G4double kineticEnergy, G4double gammaEnergy)
{
// supression due to the LPM effect+polarisation of the medium/
// supression due to the polarisation alone
G4double totEnergy = kineticEnergy+electron_mass_c2 ;
G4double totEnergySquare = totEnergy*totEnergy ;
G4double LPMEnergy = LPMconstant*(material->GetRadlen()) ;
G4double gammaEnergySquare = gammaEnergy*gammaEnergy ;
G4double electronDensity = material->GetElectronDensity();
G4double sp = gammaEnergySquare/
(gammaEnergySquare+MigdalConstant*totEnergySquare*electronDensity);
G4double supr = 1.0;
if (LPMFlag()) {
G4double s2lpm = LPMEnergy*gammaEnergy/totEnergySquare;
if (s2lpm < 1.) {
G4double LPMgEnergyLimit = totEnergySquare/LPMEnergy ;
G4double LPMgEnergyLimit2 = LPMgEnergyLimit*LPMgEnergyLimit;
G4double splim = LPMgEnergyLimit2/
(LPMgEnergyLimit2+MigdalConstant*totEnergySquare*electronDensity);
G4double w = 1.+1./splim ;
if ((1.-sp) < 1.e-6) w = s2lpm*(3.-sp);
else w = s2lpm*(1.+1./sp);
supr = (sqrt(w*w+4.*s2lpm)-w)/(sqrt(w*w+4.)-w) ;
supr /= sp;
}
}
return supr;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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