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geant4/source/processes/electromagnetic/standard/src/G4MollerBhabhaModel.cc
T
Gabriele Cosmo fe73f43734 Import Geant4 8.2.0 source tree
2016-06-09 14:55:03 +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. *
// ********************************************************************
//
// $Id: G4MollerBhabhaModel.cc,v 1.28 2006/08/28 17:44:36 vnivanch Exp $
// GEANT4 tag $Name: geant4-08-02 $
//
// -------------------------------------------------------------------
//
// 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 "G4Electron.hh"
#include "G4Positron.hh"
#include "Randomize.hh"
#include "G4ParticleChangeForLoss.hh"
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
using namespace std;
G4MollerBhabhaModel::G4MollerBhabhaModel(const G4ParticleDefinition* p,
const G4String& nam)
: G4VEmModel(nam),
particle(0),
isElectron(true),
twoln10(2.0*log(10.0)),
lowLimit(0.2*keV)
{
theElectron = G4Electron::Electron();
if(p) SetParticle(p);
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4MollerBhabhaModel::~G4MollerBhabhaModel()
{}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4MollerBhabhaModel::SetParticle(const G4ParticleDefinition* p)
{
particle = p;
if(p != theElectron) isElectron = false;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MollerBhabhaModel::MinEnergyCut(const G4ParticleDefinition*,
const G4MaterialCutsCouple* couple)
{
G4double electronDensity = couple->GetMaterial()->GetElectronDensity();
G4double Zeff = electronDensity/couple->GetMaterial()->GetTotNbOfAtomsPerVolume();
return 0.25*sqrt(Zeff)*keV;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4MollerBhabhaModel::Initialise(const G4ParticleDefinition* p,
const G4DataVector&)
{
if(!particle) SetParticle(p);
if(pParticleChange)
fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*>
(pParticleChange);
else
fParticleChange = new G4ParticleChangeForLoss();
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MollerBhabhaModel::ComputeCrossSectionPerElectron(
const G4ParticleDefinition* p,
G4double kineticEnergy,
G4double cutEnergy,
G4double maxEnergy)
{
if(!particle) SetParticle(p);
G4double cross = 0.0;
G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
tmax = min(maxEnergy, tmax);
if(cutEnergy < tmax) {
G4double xmin = cutEnergy/kineticEnergy;
G4double xmax = tmax/kineticEnergy;
G4double gam = kineticEnergy/electron_mass_c2 + 1.0;
G4double gamma2= gam*gam;
G4double beta2 = 1.0 - 1.0/gamma2;
//Moller (e-e-) scattering
if (isElectron) {
G4double g = (2.0*gam - 1.0)/gamma2;
cross = ((xmax - xmin)*(1.0 - g + 1.0/(xmin*xmax)
+ 1.0/((1.0-xmin)*(1.0 - xmax)))
- g*log( 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*log(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)
{
G4double cross = Z*ComputeCrossSectionPerElectron
(p,kineticEnergy,cutEnergy,maxEnergy);
return cross;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MollerBhabhaModel::CrossSectionPerVolume(
const G4Material* material,
const G4ParticleDefinition* p,
G4double kineticEnergy,
G4double cutEnergy,
G4double maxEnergy)
{
G4double eDensity = material->GetElectronDensity();
G4double cross = eDensity*ComputeCrossSectionPerElectron
(p,kineticEnergy,cutEnergy,maxEnergy);
return cross;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4MollerBhabhaModel::ComputeDEDXPerVolume(
const G4Material* material,
const G4ParticleDefinition* p,
G4double kineticEnergy,
G4double cutEnergy)
{
if(!particle) SetParticle(p);
// calculate the dE/dx due to the ionization by Seltzer-Berger formula
G4double electronDensity = material->GetElectronDensity();
G4double Zeff = electronDensity/material->GetTotNbOfAtomsPerVolume();
G4double th = 0.25*sqrt(Zeff)*keV;
G4double tkin = kineticEnergy;
G4bool lowEnergy = false;
if (kineticEnergy < th) {
tkin = th;
lowEnergy = true;
}
G4double tau = tkin/electron_mass_c2;
G4double gam = tau + 1.0;
G4double gamma2= gam*gam;
G4double beta2 = 1. - 1./gamma2;
G4double bg2 = beta2*gamma2;
G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
eexc /= electron_mass_c2;
G4double eexc2 = eexc*eexc;
G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin))/electron_mass_c2;
G4double dedx;
// electron
if (isElectron) {
dedx = log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2
+ log((tau-d)*d) + tau/(tau-d)
+ (0.5*d*d + (2.0*tau + 1.)*log(1. - d/tau))/gamma2;
//positron
} else {
G4double d2 = d*d*0.5;
G4double d3 = d2*d/1.5;
G4double d4 = d3*d*3.75;
G4double y = 1.0/(1.0 + gam);
dedx = log(2.0*(tau + 2.0)/eexc2) + log(tau*d)
- beta2*(tau + 2.0*d - y*(3.0*d2
+ y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau;
}
//density correction
G4double cden = material->GetIonisation()->GetCdensity();
G4double mden = material->GetIonisation()->GetMdensity();
G4double aden = material->GetIonisation()->GetAdensity();
G4double x0den = material->GetIonisation()->GetX0density();
G4double x1den = material->GetIonisation()->GetX1density();
G4double x = log(bg2)/twoln10;
if (x >= x0den) {
dedx -= twoln10*x - cden;
if (x < x1den) dedx -= aden*pow(x1den-x, mden);
}
// now you can compute the total ionization loss
dedx *= twopi_mc2_rcl2*electronDensity/beta2;
if (dedx < 0.0) dedx = 0.0;
// lowenergy extrapolation
if (lowEnergy) {
if (kineticEnergy >= lowLimit) dedx *= sqrt(tkin/kineticEnergy);
else dedx *= sqrt(tkin*kineticEnergy)/lowLimit;
}
return dedx;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
std::vector<G4DynamicParticle*>* G4MollerBhabhaModel::SampleSecondaries(
const G4MaterialCutsCouple*,
const G4DynamicParticle* dp,
G4double tmin,
G4double maxEnergy)
{
G4double tmax = std::min(maxEnergy, MaxSecondaryKinEnergy(dp));
if(tmin >= tmax) return 0;
G4double kineticEnergy = dp->GetKineticEnergy();
G4double energy = kineticEnergy + electron_mass_c2;
G4double totalMomentum = sqrt(kineticEnergy*(energy + 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, q, grej;
G4ThreeVector direction = dp->GetMomentumDirection();
//Moller (e-e-) scattering
if (isElectron) {
G4double g = (2.0*gam - 1.0)/gamma2;
G4double y = 1.0 - xmax;
grej = 1.0 - g*xmax + xmax*xmax*(1.0 - g + (1.0 - g*y)/(y*y));
do {
q = G4UniformRand();
x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
y = 1.0 - x;
z = 1.0 - g*x + x*x*(1.0 - g + (1.0 - g*y)/(y*y));
/*
if(z > grej) {
G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
<< "Majorant " << grej << " < "
<< z << " for x= " << x
<< " e-e- scattering"
<< G4endl;
}
*/
} while(grej * G4UniformRand() > 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 = -xmin*b1;
grej += y*b2;
grej -= xmin*xmin*xmin*b3;
grej += y*y*b4;
grej *= beta2;
grej += 1.0;
do {
q = G4UniformRand();
x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
z = -x*b1;
y = x*x;
z += y*b2;
y *= x;
z -= y*b3;
y *= x;
z += y*b4;
z *= beta2;
z += 1.0;
/*
if(z > grej) {
G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
<< "Majorant " << grej << " < "
<< z << " for x= " << x
<< " e+e- scattering"
<< G4endl;
}
*/
} while(grej * G4UniformRand() > z);
}
G4double deltaKinEnergy = x * kineticEnergy;
G4double deltaMomentum =
sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
G4double cost = deltaKinEnergy * (energy + electron_mass_c2) /
(deltaMomentum * totalMomentum);
G4double sint = 1.0 - cost*cost;
if(sint > 0.0) sint = sqrt(sint);
G4double phi = twopi * G4UniformRand() ;
G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost) ;
deltaDirection.rotateUz(direction);
// primary change
kineticEnergy -= deltaKinEnergy;
fParticleChange->SetProposedKineticEnergy(kineticEnergy);
if(kineticEnergy > DBL_MIN) {
G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection;
direction = dir.unit();
fParticleChange->SetProposedMomentumDirection(direction);
}
// create G4DynamicParticle object for delta ray
std::vector<G4DynamicParticle*>* vdp = new std::vector<G4DynamicParticle*>;
G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
deltaDirection,deltaKinEnergy);
vdp->push_back(delta);
return vdp;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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