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geant4/source/processes/electromagnetic/standard/src/G4MollerBhabhaModel.cc
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Gabriele Cosmo c07cea1fe0 Import Geant4 11.1.0.beta source tree
2022-07-01 10:44:02 +02:00

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//
// ********************************************************************
// * License and Disclaimer *
// * *
// * The Geant4 software is copyright of the Copyright Holders of *
// * the Geant4 Collaboration. It is provided under the terms and *
// * conditions of the Geant4 Software License, included in the file *
// * LICENSE and available at http://cern.ch/geant4/license . These *
// * include a list of copyright holders. *
// * *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work make any representation or warranty, express or implied, *
// * regarding this software system or assume any liability for its *
// * use. Please see the license in the file LICENSE and URL above *
// * for the full disclaimer and the limitation of liability. *
// * *
// * 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 *
// * use in resulting scientific publications, and indicate your *
// * acceptance of all terms of the Geant4 Software license. *
// ********************************************************************
//
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name: G4MollerBhabhaModel
//
// Author: Vladimir Ivanchenko on base of Laszlo Urban code
//
// Creation date: 03.01.2002
//
// Modifications:
//
// 13-11-02 Minor fix - use normalised direction (V.Ivanchenko)
// 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)
// 27-01-03 Make models region aware (V.Ivanchenko)
// 13-02-03 Add name (V.Ivanchenko)
// 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
// 25-07-05 Add protection in calculation of recoil direction for the case
// of complete energy transfer from e+ to e- (V.Ivanchenko)
// 06-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
// 15-05-06 Fix MinEnergyCut (V.Ivanchenko)
//
//
// Class Description:
//
// Implementation of energy loss and delta-electron production by e+/e-
//
// -------------------------------------------------------------------
//
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
#include "G4MollerBhabhaModel.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4Electron.hh"
#include "G4Positron.hh"
#include "Randomize.hh"
#include "G4ParticleChangeForLoss.hh"
#include "G4Log.hh"
#include "G4DeltaAngle.hh"
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
using namespace std;
G4MollerBhabhaModel::G4MollerBhabhaModel(const G4ParticleDefinition* p,
const G4String& nam)
: G4VEmModel(nam),
particle(nullptr),
isElectron(true),
twoln10(2.0*G4Log(10.0)),
lowLimit(0.02*keV),
isInitialised(false)
{
theElectron = G4Electron::Electron();
if(nullptr != p) { SetParticle(p); }
fParticleChange = nullptr;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4MollerBhabhaModel::~G4MollerBhabhaModel() = default;
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MollerBhabhaModel::MaxSecondaryEnergy(const G4ParticleDefinition*,
G4double kinEnergy)
{
G4double tmax = kinEnergy;
if(isElectron) { tmax *= 0.5; }
return tmax;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4MollerBhabhaModel::Initialise(const G4ParticleDefinition* p,
const G4DataVector&)
{
if(p != particle) { SetParticle(p); }
if(isInitialised) { return; }
isInitialised = true;
fParticleChange = GetParticleChangeForLoss();
if(UseAngularGeneratorFlag() && !GetAngularDistribution()) {
SetAngularDistribution(new G4DeltaAngle());
}
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MollerBhabhaModel::ComputeCrossSectionPerElectron(
const G4ParticleDefinition* p, G4double kineticEnergy,
G4double cutEnergy, G4double maxEnergy)
{
if(p != particle) { SetParticle(p); }
G4double cross = 0.0;
G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
tmax = std::min(maxEnergy, tmax);
//G4cout << "E= " << kineticEnergy << " cut= " << cutEnergy
// << " Emax= " << tmax << G4endl;
if(cutEnergy < tmax) {
G4double xmin = cutEnergy/kineticEnergy;
G4double xmax = tmax/kineticEnergy;
G4double tau = kineticEnergy/electron_mass_c2;
G4double gam = tau + 1.0;
G4double gamma2= gam*gam;
G4double beta2 = tau*(tau + 2)/gamma2;
//Moller (e-e-) scattering
if (isElectron) {
G4double gg = (2.0*gam - 1.0)/gamma2;
cross = ((xmax - xmin)*(1.0 - gg + 1.0/(xmin*xmax)
+ 1.0/((1.0-xmin)*(1.0 - xmax)))
- gg*G4Log( xmax*(1.0 - xmin)/(xmin*(1.0 - xmax)) ) ) / beta2;
//Bhabha (e+e-) scattering
} else {
G4double y = 1.0/(1.0 + gam);
G4double y2 = y*y;
G4double y12 = 1.0 - 2.0*y;
G4double b1 = 2.0 - y2;
G4double b2 = y12*(3.0 + y2);
G4double y122= y12*y12;
G4double b4 = y122*y12;
G4double b3 = b4 + y122;
cross = (xmax - xmin)*(1.0/(beta2*xmin*xmax) + b2
- 0.5*b3*(xmin + xmax)
+ b4*(xmin*xmin + xmin*xmax + xmax*xmax)/3.0)
- b1*G4Log(xmax/xmin);
}
cross *= twopi_mc2_rcl2/kineticEnergy;
}
return cross;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MollerBhabhaModel::ComputeCrossSectionPerAtom(
const G4ParticleDefinition* p,
G4double kineticEnergy,
G4double Z, G4double,
G4double cutEnergy,
G4double maxEnergy)
{
return Z*ComputeCrossSectionPerElectron(p,kineticEnergy,cutEnergy,maxEnergy);
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MollerBhabhaModel::CrossSectionPerVolume(
const G4Material* material,
const G4ParticleDefinition* p,
G4double kinEnergy,
G4double cutEnergy,
G4double maxEnergy)
{
G4double eDensity = material->GetElectronDensity();
return eDensity*ComputeCrossSectionPerElectron(p,kinEnergy,cutEnergy,maxEnergy);
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MollerBhabhaModel::ComputeDEDXPerVolume(
const G4Material* material,
const G4ParticleDefinition* p,
G4double kineticEnergy,
G4double cut)
{
if(p != particle) { SetParticle(p); }
// calculate the dE/dx due to the ionization by Seltzer-Berger formula
// checl low-energy limit
G4double electronDensity = material->GetElectronDensity();
G4double Zeff = material->GetIonisation()->GetZeffective();
G4double th = 0.25*sqrt(Zeff)*keV;
G4double tkin = std::max(kineticEnergy, th);
G4double tau = tkin/electron_mass_c2;
G4double gam = tau + 1.0;
G4double gamma2= gam*gam;
G4double bg2 = tau*(tau + 2);
G4double beta2 = bg2/gamma2;
G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
eexc /= electron_mass_c2;
G4double eexc2 = eexc*eexc;
G4double d = std::min(cut, MaxSecondaryEnergy(p, tkin))/electron_mass_c2;
G4double dedx;
// electron
if (isElectron) {
dedx = G4Log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2
+ G4Log((tau-d)*d) + tau/(tau-d)
+ (0.5*d*d + (2.0*tau + 1.)*G4Log(1. - d/tau))/gamma2;
//positron
} else {
G4double d2 = d*d*0.5;
G4double d3 = d2*d/1.5;
G4double d4 = d3*d*0.75;
G4double y = 1.0/(1.0 + gam);
dedx = G4Log(2.0*(tau + 2.0)/eexc2) + G4Log(tau*d)
- beta2*(tau + 2.0*d - y*(3.0*d2
+ y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau;
}
//density correction
G4double x = G4Log(bg2)/twoln10;
dedx -= material->GetIonisation()->DensityCorrection(x);
// now you can compute the total ionization loss
dedx *= twopi_mc2_rcl2*electronDensity/beta2;
if (dedx < 0.0) { dedx = 0.0; }
// lowenergy extrapolation
if (kineticEnergy < th) {
x = kineticEnergy/th;
if(x > 0.25) { dedx /= sqrt(x); }
else { dedx *= 1.4*sqrt(x)/(0.1 + x); }
}
return dedx;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void
G4MollerBhabhaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
const G4MaterialCutsCouple* couple,
const G4DynamicParticle* dp,
G4double cutEnergy,
G4double maxEnergy)
{
G4double kineticEnergy = dp->GetKineticEnergy();
//G4cout << "G4MollerBhabhaModel::SampleSecondaries: E= " << kineticEnergy
// << " in " << couple->GetMaterial()->GetName() << G4endl;
G4double tmax;
G4double tmin = cutEnergy;
if(isElectron) {
tmax = 0.5*kineticEnergy;
} else {
tmax = kineticEnergy;
}
if(maxEnergy < tmax) { tmax = maxEnergy; }
if(tmin >= tmax) { return; }
G4double energy = kineticEnergy + electron_mass_c2;
G4double xmin = tmin/kineticEnergy;
G4double xmax = tmax/kineticEnergy;
G4double gam = energy/electron_mass_c2;
G4double gamma2 = gam*gam;
G4double beta2 = 1.0 - 1.0/gamma2;
G4double x, z, grej;
CLHEP::HepRandomEngine* rndmEngine = G4Random::getTheEngine();
G4double rndm[2];
//Moller (e-e-) scattering
if (isElectron) {
G4double gg = (2.0*gam - 1.0)/gamma2;
G4double y = 1.0 - xmax;
grej = 1.0 - gg*xmax + xmax*xmax*(1.0 - gg + (1.0 - gg*y)/(y*y));
do {
rndmEngine->flatArray(2, rndm);
x = xmin*xmax/(xmin*(1.0 - rndm[0]) + xmax*rndm[0]);
y = 1.0 - x;
z = 1.0 - gg*x + x*x*(1.0 - gg + (1.0 - gg*y)/(y*y));
/*
if(z > grej) {
G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
<< "Majorant " << grej << " < "
<< z << " for x= " << x
<< " e-e- scattering"
<< G4endl;
}
*/
// Loop checking, 03-Aug-2015, Vladimir Ivanchenko
} while(grej * rndm[1] > z);
//Bhabha (e+e-) scattering
} else {
G4double y = 1.0/(1.0 + gam);
G4double y2 = y*y;
G4double y12 = 1.0 - 2.0*y;
G4double b1 = 2.0 - y2;
G4double b2 = y12*(3.0 + y2);
G4double y122= y12*y12;
G4double b4 = y122*y12;
G4double b3 = b4 + y122;
y = xmax*xmax;
grej = 1.0 + (y*y*b4 - xmin*xmin*xmin*b3 + y*b2 - xmin*b1)*beta2;
do {
rndmEngine->flatArray(2, rndm);
x = xmin*xmax/(xmin*(1.0 - rndm[0]) + xmax*rndm[0]);
y = x*x;
z = 1.0 + (y*y*b4 - x*y*b3 + y*b2 - x*b1)*beta2;
/*
if(z > grej) {
G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
<< "Majorant " << grej << " < "
<< z << " for x= " << x
<< " e+e- scattering"
<< G4endl;
}
*/
// Loop checking, 03-Aug-2015, Vladimir Ivanchenko
} while(grej * rndm[1] > z);
}
G4double deltaKinEnergy = x * kineticEnergy;
G4ThreeVector deltaDirection;
if(UseAngularGeneratorFlag()) {
const G4Material* mat = couple->GetMaterial();
G4int Z = SelectRandomAtomNumber(mat);
deltaDirection =
GetAngularDistribution()->SampleDirection(dp, deltaKinEnergy, Z, mat);
} else {
G4double deltaMomentum =
sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
G4double cost = deltaKinEnergy * (energy + electron_mass_c2) /
(deltaMomentum * dp->GetTotalMomentum());
if(cost > 1.0) { cost = 1.0; }
G4double sint = sqrt((1.0 - cost)*(1.0 + cost));
G4double phi = twopi * rndmEngine->flat() ;
deltaDirection.set(sint*cos(phi),sint*sin(phi), cost) ;
deltaDirection.rotateUz(dp->GetMomentumDirection());
}
// create G4DynamicParticle object for delta ray
auto delta = new G4DynamicParticle(theElectron,deltaDirection,deltaKinEnergy);
vdp->push_back(delta);
// primary change
kineticEnergy -= deltaKinEnergy;
G4ThreeVector finalP = dp->GetMomentum() - delta->GetMomentum();
finalP = finalP.unit();
fParticleChange->SetProposedKineticEnergy(kineticEnergy);
fParticleChange->SetProposedMomentumDirection(finalP);
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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