Gabriele Cosmo
266 lines
9.7 KiB
C++
266 lines
9.7 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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// $Id: G4LowEnergyCompton.cc,v 1.41 2006/06/29 19:40:15 gunter Exp $
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// GEANT4 tag $Name: geant4-08-01 $
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//
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// Author: A. Forti
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// Maria Grazia Pia (Maria.Grazia.Pia@cern.ch)
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//
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// History:
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// --------
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// Added Livermore data table construction methods A. Forti
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// Modified BuildMeanFreePath to read new data tables A. Forti
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// Modified PostStepDoIt to insert sampling with EPDL97 data A. Forti
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// Added SelectRandomAtom A. Forti
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// Added map of the elements A. Forti
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// 24.04.2001 V.Ivanchenko - Remove RogueWave
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// 06.08.2001 MGP - Revised according to a design iteration
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// 22.01.2003 V.Ivanchenko - Cut per region
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// 10.03.2003 V.Ivanchenko - Remove CutPerMaterial warning
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// 24.04.2003 V.Ivanchenko - Cut per region mfpt
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//
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// -------------------------------------------------------------------
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#include "G4LowEnergyCompton.hh"
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#include "Randomize.hh"
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#include "G4ParticleDefinition.hh"
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#include "G4Track.hh"
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#include "G4Step.hh"
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#include "G4ForceCondition.hh"
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#include "G4Gamma.hh"
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#include "G4Electron.hh"
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#include "G4DynamicParticle.hh"
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#include "G4VParticleChange.hh"
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#include "G4ThreeVector.hh"
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#include "G4EnergyLossTables.hh"
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#include "G4VCrossSectionHandler.hh"
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#include "G4CrossSectionHandler.hh"
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#include "G4VEMDataSet.hh"
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#include "G4CompositeEMDataSet.hh"
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#include "G4VDataSetAlgorithm.hh"
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#include "G4LogLogInterpolation.hh"
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#include "G4VRangeTest.hh"
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#include "G4RangeTest.hh"
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#include "G4MaterialCutsCouple.hh"
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G4LowEnergyCompton::G4LowEnergyCompton(const G4String& processName)
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: G4VDiscreteProcess(processName),
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lowEnergyLimit(250*eV),
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highEnergyLimit(100*GeV),
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intrinsicLowEnergyLimit(10*eV),
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intrinsicHighEnergyLimit(100*GeV)
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{
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if (lowEnergyLimit < intrinsicLowEnergyLimit ||
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highEnergyLimit > intrinsicHighEnergyLimit)
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{
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G4Exception("G4LowEnergyCompton::G4LowEnergyCompton - energy outside intrinsic process validity range");
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}
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crossSectionHandler = new G4CrossSectionHandler;
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G4VDataSetAlgorithm* scatterInterpolation = new G4LogLogInterpolation;
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G4String scatterFile = "comp/ce-sf-";
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scatterFunctionData = new G4CompositeEMDataSet(scatterInterpolation, 1., 1.);
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scatterFunctionData->LoadData(scatterFile);
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meanFreePathTable = 0;
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rangeTest = new G4RangeTest;
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if (verboseLevel > 0)
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{
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G4cout << GetProcessName() << " is created " << G4endl
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<< "Energy range: "
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<< lowEnergyLimit / keV << " keV - "
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<< highEnergyLimit / GeV << " GeV"
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<< G4endl;
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}
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}
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G4LowEnergyCompton::~G4LowEnergyCompton()
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{
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delete meanFreePathTable;
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delete crossSectionHandler;
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delete scatterFunctionData;
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delete rangeTest;
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}
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void G4LowEnergyCompton::BuildPhysicsTable(const G4ParticleDefinition& )
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{
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crossSectionHandler->Clear();
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G4String crossSectionFile = "comp/ce-cs-";
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crossSectionHandler->LoadData(crossSectionFile);
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delete meanFreePathTable;
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meanFreePathTable = crossSectionHandler->BuildMeanFreePathForMaterials();
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}
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G4VParticleChange* G4LowEnergyCompton::PostStepDoIt(const G4Track& aTrack,
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const G4Step& aStep)
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{
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// The scattered gamma energy is sampled according to Klein - Nishina formula.
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// then accepted or rejected depending on the Scattering Function multiplied
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// by factor from Klein - Nishina formula.
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// Expression of the angular distribution as Klein Nishina
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// angular and energy distribution and Scattering fuctions is taken from
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// D. E. Cullen "A simple model of photon transport" Nucl. Instr. Meth.
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// Phys. Res. B 101 (1995). Method of sampling with form factors is different
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// data are interpolated while in the article they are fitted.
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// Reference to the article is from J. Stepanek New Photon, Positron
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// and Electron Interaction Data for GEANT in Energy Range from 1 eV to 10
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// TeV (draft).
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// The random number techniques of Butcher & Messel are used
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// (Nucl Phys 20(1960),15).
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aParticleChange.Initialize(aTrack);
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// Dynamic particle quantities
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const G4DynamicParticle* incidentPhoton = aTrack.GetDynamicParticle();
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G4double photonEnergy0 = incidentPhoton->GetKineticEnergy();
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if (photonEnergy0 <= lowEnergyLimit)
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{
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aParticleChange.ProposeTrackStatus(fStopAndKill);
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aParticleChange.ProposeEnergy(0.);
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aParticleChange.ProposeLocalEnergyDeposit(photonEnergy0);
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return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
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}
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G4double e0m = photonEnergy0 / electron_mass_c2 ;
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G4ParticleMomentum photonDirection0 = incidentPhoton->GetMomentumDirection();
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// Select randomly one element in the current material
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const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple();
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G4int Z = crossSectionHandler->SelectRandomAtom(couple,photonEnergy0);
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G4double epsilon0 = 1. / (1. + 2. * e0m);
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G4double epsilon0Sq = epsilon0 * epsilon0;
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G4double alpha1 = -std::log(epsilon0);
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G4double alpha2 = 0.5 * (1. - epsilon0Sq);
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G4double wlPhoton = h_Planck*c_light/photonEnergy0;
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// Sample the energy of the scattered photon
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G4double epsilon;
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G4double epsilonSq;
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G4double oneCosT;
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G4double sinT2;
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G4double gReject;
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do
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{
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if ( alpha1/(alpha1+alpha2) > G4UniformRand())
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{
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epsilon = std::exp(-alpha1 * G4UniformRand()); // std::pow(epsilon0,G4UniformRand())
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epsilonSq = epsilon * epsilon;
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}
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else
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{
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epsilonSq = epsilon0Sq + (1. - epsilon0Sq) * G4UniformRand();
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epsilon = std::sqrt(epsilonSq);
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}
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oneCosT = (1. - epsilon) / ( epsilon * e0m);
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sinT2 = oneCosT * (2. - oneCosT);
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G4double x = std::sqrt(oneCosT/2.) / (wlPhoton/cm);
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G4double scatteringFunction = scatterFunctionData->FindValue(x,Z-1);
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gReject = (1. - epsilon * sinT2 / (1. + epsilonSq)) * scatteringFunction;
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} while(gReject < G4UniformRand()*Z);
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G4double cosTheta = 1. - oneCosT;
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G4double sinTheta = std::sqrt (sinT2);
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G4double phi = twopi * G4UniformRand() ;
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G4double dirx = sinTheta * std::cos(phi);
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G4double diry = sinTheta * std::sin(phi);
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G4double dirz = cosTheta ;
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// Update G4VParticleChange for the scattered photon
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G4ThreeVector photonDirection1(dirx,diry,dirz);
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photonDirection1.rotateUz(photonDirection0);
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aParticleChange.ProposeMomentumDirection(photonDirection1) ;
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G4double photonEnergy1 = epsilon * photonEnergy0;
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if (photonEnergy1 > 0.)
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{
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aParticleChange.ProposeEnergy(photonEnergy1) ;
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}
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else
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{
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aParticleChange.ProposeEnergy(0.) ;
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aParticleChange.ProposeTrackStatus(fStopAndKill);
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}
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// Kinematics of the scattered electron
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G4double eKineticEnergy = photonEnergy0 - photonEnergy1;
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// Generate the electron only if with large enough range w.r.t. cuts and safety
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G4double safety = aStep.GetPostStepPoint()->GetSafety();
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if (rangeTest->Escape(G4Electron::Electron(),couple,eKineticEnergy,safety))
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{
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G4double eMomentum = std::sqrt(eKineticEnergy*(eKineticEnergy+2.*electron_mass_c2));
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G4ThreeVector eDirection((photonEnergy0 * photonDirection0 -
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photonEnergy1 * photonDirection1) * (1./eMomentum));
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G4DynamicParticle* electron = new G4DynamicParticle (G4Electron::Electron(),
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eDirection,eKineticEnergy) ;
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aParticleChange.SetNumberOfSecondaries(1);
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aParticleChange.AddSecondary(electron);
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aParticleChange.ProposeLocalEnergyDeposit(0.);
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}
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else
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{
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aParticleChange.SetNumberOfSecondaries(0);
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aParticleChange.ProposeLocalEnergyDeposit(eKineticEnergy);
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}
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return G4VDiscreteProcess::PostStepDoIt( aTrack, aStep);
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}
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G4bool G4LowEnergyCompton::IsApplicable(const G4ParticleDefinition& particle)
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{
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return ( &particle == G4Gamma::Gamma() );
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}
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G4double G4LowEnergyCompton::GetMeanFreePath(const G4Track& track,
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G4double, // previousStepSize
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G4ForceCondition*)
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{
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const G4DynamicParticle* photon = track.GetDynamicParticle();
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G4double energy = photon->GetKineticEnergy();
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const G4MaterialCutsCouple* couple = track.GetMaterialCutsCouple();
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size_t materialIndex = couple->GetIndex();
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G4double meanFreePath;
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if (energy > highEnergyLimit) meanFreePath = meanFreePathTable->FindValue(highEnergyLimit,materialIndex);
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else if (energy < lowEnergyLimit) meanFreePath = DBL_MAX;
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else meanFreePath = meanFreePathTable->FindValue(energy,materialIndex);
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return meanFreePath;
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}
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