lars/geant4
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
96c8bcd0af6199eb0c12c400a8498add55e6c23e
geant4/source/processes/electromagnetic/standard/src/G4PolarizedComptonScattering.cc
T
Gabriele Cosmo 96c8bcd0af Import Geant4 9.1.0 source tree
2016-06-09 15:37:50 +02:00

289 lines
10 KiB
C++
Raw Blame History

//
// ********************************************************************
// * 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: G4PolarizedComptonScattering.cc,v 1.16 2006/06/29 19:53:30 gunter Exp $
// GEANT4 tag $Name: geant4-09-01 $
//
//
//---------- G4PolarizedComptonScattering physics process ----------------------
// by Vicente Lara, March 1998
//
// -----------------------------------------------------------------------------
// Corrections by Rui Curado da Silva (Nov. 2000)
// - Sampling of Phi
// - Depolarization probability
//
// 13-07-01, DoIt: suppression of production cut for the electron (mma)
// 20-09-01, DoIt: fminimalEnergy = 1*eV (mma)
// 04-05-05, Inheritance from ComptonScattering52 (V.Ivanchenko)
// 30-01-06, DoIt : return G4ComptonScattering52::PostStepDoIt(aTrack,aStep) mma
//
// -----------------------------------------------------------------------------
#include "G4PolarizedComptonScattering.hh"
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
using namespace std;
G4PolarizedComptonScattering::G4PolarizedComptonScattering(
const G4String& processName)
: G4ComptonScattering52 (processName)
{ }
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4VParticleChange* G4PolarizedComptonScattering::PostStepDoIt(
const G4Track& aTrack,
const G4Step& aStep)
//
// The scattered gamma energy is sampled according to Klein - Nishina formula.
// The random number techniques of Butcher & Messel are used
// (Nuc Phys 20(1960),15).
// GEANT4 internal units
//
// Note : Effects due to binding of atomic electrons are negliged.
{
aParticleChange.Initialize(aTrack);
const G4DynamicParticle* aDynamicGamma = aTrack.GetDynamicParticle();
G4ThreeVector GammaPolarization0 = aDynamicGamma->GetPolarization();
if (std::abs(GammaPolarization0.mag() - 1.e0) > 1.e-14)
return G4ComptonScattering52::PostStepDoIt(aTrack,aStep);
G4double GammaEnergy0 = aDynamicGamma->GetKineticEnergy();
G4double E0_m = GammaEnergy0 / electron_mass_c2;
G4ParticleMomentum GammaDirection0 = aDynamicGamma->GetMomentumDirection();
//
// sample the energy rate of the scattered gamma
//
G4double epsilon, epsilonsq, onecost, sint2, greject;
G4double epsilon0 = 1./(1. + 2*E0_m) , epsilon0sq = epsilon0*epsilon0;
G4double alpha1 = - log(epsilon0) , alpha2 = 0.5*(1.- epsilon0sq);
do {
if (alpha1/(alpha1+alpha2) > G4UniformRand())
{ epsilon = exp(-alpha1*G4UniformRand()); // epsilon0**r
epsilonsq = epsilon*epsilon; }
else {
epsilonsq = epsilon0sq + (1.- epsilon0sq)*G4UniformRand();
epsilon = sqrt(epsilonsq);
};
onecost = (1.- epsilon)/(epsilon*E0_m);
sint2 = onecost*(2.-onecost);
greject = 1. - epsilon*sint2/(1.+ epsilonsq);
} while (greject < G4UniformRand());
//
// Phi determination
//
G4double minimum=0., maximum=twopi, middle=0., resolution=0.001;
G4double Rand = G4UniformRand();
int j = 0;
while ((j < 100) && (std::abs(SetPhi(epsilon,sint2,middle,Rand)) > resolution))
{
middle = (maximum + minimum)/2;
if (SetPhi(epsilon,sint2,middle,Rand)*
SetPhi(epsilon,sint2,minimum,Rand)<0) maximum = middle;
else minimum = middle;
j++;
}
//
// scattered gamma angles. ( Z - axis along the parent gamma)
//
G4double cosTeta = 1. - onecost , sinTeta = sqrt (sint2);
G4double Phi = middle;
G4double dirx = sinTeta*cos(Phi), diry = sinTeta*sin(Phi), dirz = cosTeta;
//
// update G4VParticleChange for the scattered gamma
//
G4double GammaEnergy1 = epsilon*GammaEnergy0;
// New polarization
//
G4ThreeVector GammaPolarization1 = SetNewPolarization(epsilon,sint2,Phi,
cosTeta,
GammaPolarization0);
// Set new direction
G4ThreeVector GammaDirection1 ( dirx,diry,dirz );
// Change reference frame.
SystemOfRefChange(GammaDirection0,GammaDirection1,
GammaPolarization0,GammaPolarization1);
G4double localEnergyDeposit = 0.;
if (GammaEnergy1 > fminimalEnergy)
{
aParticleChange.ProposeEnergy(GammaEnergy1);
}
else
{
localEnergyDeposit += GammaEnergy1;
aParticleChange.ProposeEnergy(0.) ;
aParticleChange.ProposeTrackStatus(fStopAndKill);
}
//
// kinematic of the scattered electron
//
G4double ElecKineEnergy = GammaEnergy0 - GammaEnergy1;
if (ElecKineEnergy > fminimalEnergy)
{
G4double ElecMomentum = sqrt(ElecKineEnergy*
(ElecKineEnergy+2.*electron_mass_c2));
G4ThreeVector ElecDirection (
(GammaEnergy0*GammaDirection0 - GammaEnergy1*GammaDirection1)
*(1./ElecMomentum));
// create G4DynamicParticle object for the electron.
G4DynamicParticle* aElectron= new G4DynamicParticle (
G4Electron::Electron(),ElecDirection,ElecKineEnergy);
aParticleChange.SetNumberOfSecondaries(1);
aParticleChange.AddSecondary( aElectron );
}
else
{
aParticleChange.SetNumberOfSecondaries(0);
localEnergyDeposit += ElecKineEnergy;
}
aParticleChange.ProposeLocalEnergyDeposit(localEnergyDeposit);
// Reset NbOfInteractionLengthLeft and return aParticleChange
return G4VDiscreteProcess::PostStepDoIt( aTrack, aStep);
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4double G4PolarizedComptonScattering::SetPhi(G4double EnergyRate,
G4double sinsqrth,
G4double phi,
G4double rand)
{
G4double cosphi = cos(phi), sinphi = sin(phi);
G4double PhiDetermination = ((twopi*rand - phi)
*(EnergyRate + 1./EnergyRate - sinsqrth))
+ (sinsqrth*sinphi*cosphi);
return PhiDetermination;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4ThreeVector G4PolarizedComptonScattering::SetNewPolarization(
G4double EnergyRate,
G4double sinsqrth,
G4double phi,
G4double costheta,
G4ThreeVector&)
{
G4double cosphi = cos(phi), sinphi = sin(phi);
//// G4double ParallelIntensityPolar = EnergyRate + 1./EnergyRate
//// + 2. - 4.*sinsqrth*cosphi*cosphi;
G4double ParallelIntensityPolar = EnergyRate + 1./EnergyRate
- 2.*sinsqrth*cosphi*cosphi;
G4double PerpendiIntensityPolar = EnergyRate + 1./EnergyRate - 2.;
G4double PolarizationDegree = sqrt(sinsqrth*sinphi*sinphi+costheta*costheta);
G4double sintheta = sqrt(sinsqrth);
G4ThreeVector GammaPolarization1;
// depolarization probability (1-P)
if ( G4UniformRand() > (PerpendiIntensityPolar/ParallelIntensityPolar) )
{
// Parallel to initial polarization
GammaPolarization1.setX(PolarizationDegree);
GammaPolarization1.setY(-sinsqrth*sinphi*cosphi/PolarizationDegree);
GammaPolarization1.setZ(-sintheta*costheta*cosphi/PolarizationDegree);
}
else
{
// Perpendicular to initial polarization
GammaPolarization1.setX(0.);
GammaPolarization1.setY(costheta/PolarizationDegree);
GammaPolarization1.setZ(-sintheta*sinphi/PolarizationDegree);
};
return GammaPolarization1;
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void G4PolarizedComptonScattering::SystemOfRefChange(G4ThreeVector& Direction0,
G4ThreeVector& Direction1,
G4ThreeVector& Polarization0,
G4ThreeVector& Polarization1)
{
// Angles for go back to the original RS
G4double cosTeta0 = Direction0.cosTheta(), sinTeta0 = sin(Direction0.theta());
G4double cosPhi0 = cos(Direction0.phi()), sinPhi0 = sin(Direction0.phi());
G4double cosPsi, sinPsi;
if (sinTeta0 != 0. )
{
cosPsi = -Polarization0.z()/sinTeta0;
if (cosPhi0 != 0.)
sinPsi = (Polarization0.y() - cosTeta0*sinPhi0*cosPsi)/cosPhi0;
else sinPsi = -Polarization0.x()/sinPhi0;
}
else
{
cosPsi = Polarization0.x()/cosTeta0;
sinPsi = Polarization0.y();
}
G4double Psi = atan(sinPsi/cosPsi);
// Rotation along Z axe
Direction1.rotateZ(Psi);
//
Direction1.rotateUz(Direction0);
aParticleChange.ProposeMomentumDirection(Direction1);
// 3 Euler angles rotation for scattered photon polarization
Polarization1.rotateZ(Psi);
Polarization1.rotateUz(Direction0);
aParticleChange.ProposePolarization(Polarization1);
}
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
Reference in New Issue View Git Blame Copy Permalink