Gabriele Cosmo
404 lines
14 KiB
C++
404 lines
14 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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//
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//
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// Author: Sebastien Incerti
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// 30 October 2008
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// on base of G4LowEnergyCompton developed by A.Forti and M.G.Pia
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//
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// History:
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// --------
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// 18 Apr 2009 V Ivanchenko Cleanup initialisation and generation of secondaries:
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// - apply internal high-energy limit only in constructor
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// - do not apply low-energy limit (default is 0)
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// - remove GetMeanFreePath method and table
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// - added protection against numerical problem in energy sampling
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// - use G4ElementSelector
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// 26 Dec 2010 V Ivanchenko Load data tables only once to avoid memory leak
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// 30 May 2011 V Ivanchenko Migration to model design for deexcitation
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#include "G4LivermoreComptonModifiedModel.hh"
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#include "G4PhysicalConstants.hh"
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#include "G4SystemOfUnits.hh"
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#include "G4Electron.hh"
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#include "G4ParticleChangeForGamma.hh"
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#include "G4LossTableManager.hh"
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#include "G4VAtomDeexcitation.hh"
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#include "G4AtomicShell.hh"
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#include "G4CrossSectionHandler.hh"
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#include "G4CompositeEMDataSet.hh"
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#include "G4LogLogInterpolation.hh"
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#include "G4Gamma.hh"
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#include "G4Exp.hh"
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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using namespace std;
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4LivermoreComptonModifiedModel::G4LivermoreComptonModifiedModel(const G4ParticleDefinition*,
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const G4String& nam)
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:G4VEmModel(nam),fParticleChange(nullptr),
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scatterFunctionData(nullptr),
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crossSectionHandler(nullptr),fAtomDeexcitation(nullptr),
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isInitialised(false)
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{
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verboseLevel=0 ;
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// Verbosity scale:
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// 0 = nothing
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// 1 = warning for energy non-conservation
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// 2 = details of energy budget
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// 3 = calculation of cross sections, file openings, sampling of atoms
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// 4 = entering in methods
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if( verboseLevel>0 )
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G4cout << "Livermore Modified Compton model is constructed " << G4endl;
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//Mark this model as "applicable" for atomic deexcitation
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SetDeexcitationFlag(true);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4LivermoreComptonModifiedModel::~G4LivermoreComptonModifiedModel()
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{
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delete crossSectionHandler;
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delete scatterFunctionData;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4LivermoreComptonModifiedModel::Initialise(const G4ParticleDefinition* particle,
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const G4DataVector& cuts)
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{
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if (verboseLevel > 2) {
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G4cout << "Calling G4LivermoreComptonModifiedModel::Initialise()" << G4endl;
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}
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if (crossSectionHandler)
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{
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crossSectionHandler->Clear();
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delete crossSectionHandler;
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}
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delete scatterFunctionData;
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// Reading of data files - all materials are read
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crossSectionHandler = new G4CrossSectionHandler;
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G4String crossSectionFile = "comp/ce-cs-";
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crossSectionHandler->LoadData(crossSectionFile);
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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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// For Doppler broadening
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shellData.SetOccupancyData();
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G4String file = "/doppler/shell-doppler";
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shellData.LoadData(file);
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InitialiseElementSelectors(particle,cuts);
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if (verboseLevel > 2) {
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G4cout << "Loaded cross section files for Livermore Modified Compton model" << G4endl;
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}
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if(isInitialised) { return; }
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isInitialised = true;
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fParticleChange = GetParticleChangeForGamma();
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fAtomDeexcitation = G4LossTableManager::Instance()->AtomDeexcitation();
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if( verboseLevel>0 ) {
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G4cout << "Livermore modified Compton model is initialized " << G4endl
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<< "Energy range: "
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<< LowEnergyLimit() / eV << " eV - "
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<< HighEnergyLimit() / GeV << " GeV"
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<< G4endl;
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}
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4LivermoreComptonModifiedModel::ComputeCrossSectionPerAtom(
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const G4ParticleDefinition*,
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G4double GammaEnergy,
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G4double Z, G4double,
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G4double, G4double)
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{
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if (verboseLevel > 3) {
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G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreComptonModifiedModel" << G4endl;
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}
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if (GammaEnergy < LowEnergyLimit())
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{ return 0.0; }
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G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
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return cs;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4LivermoreComptonModifiedModel::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
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const G4MaterialCutsCouple* couple,
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const G4DynamicParticle* aDynamicGamma,
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G4double, G4double)
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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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G4double photonEnergy0 = aDynamicGamma->GetKineticEnergy();
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if (verboseLevel > 3) {
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G4cout << "G4LivermoreComptonModifiedModel::SampleSecondaries() E(MeV)= "
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<< photonEnergy0/MeV << " in " << couple->GetMaterial()->GetName()
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<< G4endl;
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}
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// do nothing below the threshold
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// should never get here because the XS is zero below the limit
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if (photonEnergy0 < LowEnergyLimit())
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return ;
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G4double e0m = photonEnergy0 / electron_mass_c2 ;
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G4ParticleMomentum photonDirection0 = aDynamicGamma->GetMomentumDirection();
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// Select randomly one element in the current material
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const G4ParticleDefinition* particle = aDynamicGamma->GetDefinition();
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const G4Element* elm = SelectRandomAtom(couple,particle,photonEnergy0);
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G4int Z = (G4int)elm->GetZ();
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G4double epsilon0Local = 1. / (1. + 2. * e0m);
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G4double epsilon0Sq = epsilon0Local * epsilon0Local;
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G4double alpha1 = -G4Log(epsilon0Local);
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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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// std::pow(epsilon0Local,G4UniformRand())
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epsilon = G4Exp(-alpha1 * 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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// Doppler broadening - Method based on:
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// Y. Namito, S. Ban and H. Hirayama,
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// "Implementation of the Doppler Broadening of a Compton-Scattered Photon
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// into the EGS4 Code", NIM A 349, pp. 489-494, 1994
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// Maximum number of sampling iterations
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G4int maxDopplerIterations = 1000;
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G4double bindingE = 0.;
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G4double photonEoriginal = epsilon * photonEnergy0;
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G4double photonE = -1.;
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G4int iteration = 0;
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G4double systemE = 0;
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G4double ePAU = -1;
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G4int shellIdx = 0;
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G4double vel_c = 299792458;
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G4double momentum_au_to_nat = 1.992851740*std::pow(10.,-24.);
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G4double e_mass_kg = 9.10938188 * std::pow(10.,-31.);
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G4double eMax = -1;
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G4double Alpha=0;
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do
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{
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++iteration;
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// Select shell based on shell occupancy
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shellIdx = shellData.SelectRandomShell(Z);
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bindingE = shellData.BindingEnergy(Z,shellIdx);
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// Randomly sample bound electron momentum
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// (memento: the data set is in Atomic Units)
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G4double pSample = profileData.RandomSelectMomentum(Z,shellIdx);
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// Rescale from atomic units
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//Kinetic energy of target electron
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// Reverse vector projection onto scattering vector
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do {
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Alpha = G4UniformRand()*pi/2.0;
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} while(Alpha >= (pi/2.0));
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ePAU = pSample / std::cos(Alpha);
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// Convert to SI and the calculate electron energy in natural units
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G4double ePSI = ePAU * momentum_au_to_nat;
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G4double u_temp = sqrt( ((ePSI*ePSI)*(vel_c*vel_c)) / ((e_mass_kg*e_mass_kg)*(vel_c*vel_c)+(ePSI*ePSI)))/vel_c;
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G4double eEIncident = electron_mass_c2 / sqrt( 1 - (u_temp*u_temp));
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//Total energy of the system
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systemE = eEIncident+photonEnergy0;
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eMax = systemE - bindingE - electron_mass_c2;
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G4double pDoppler = pSample * fine_structure_const;
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G4double pDoppler2 = pDoppler * pDoppler;
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G4double var2 = 1. + oneCosT * e0m;
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G4double var3 = var2*var2 - pDoppler2;
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G4double var4 = var2 - pDoppler2 * cosTheta;
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G4double var = var4*var4 - var3 + pDoppler2 * var3;
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if (var > 0.)
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{
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G4double varSqrt = std::sqrt(var);
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G4double scale = photonEnergy0 / var3;
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// Random select either root
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if (G4UniformRand() < 0.5) { photonE = (var4 - varSqrt) * scale; }
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else { photonE = (var4 + varSqrt) * scale; }
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}
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else
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{
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photonE = -1.;
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}
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} while ( iteration <= maxDopplerIterations &&
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(photonE < 0. || photonE > eMax ) );
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// End of recalculation of photon energy with Doppler broadening
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// Kinematics of the scattered electron
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G4double eKineticEnergy = systemE - photonE - bindingE - electron_mass_c2;
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// protection against negative final energy: no e- is created
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G4double eDirX = 0.0;
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G4double eDirY = 0.0;
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G4double eDirZ = 1.0;
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if(eKineticEnergy < 0.0) {
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G4cout << "Error, kinetic energy of electron less than zero" << G4endl;
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}
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else{
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// Estimation of Compton electron polar angle taken from:
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// The EGSnrc Code System: Monte Carlo Simulation of Electron and Photon Transport
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// Eqn 2.2.25 Pg 42, NRCC Report PIRS-701
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G4double E_num = photonEnergy0 - photonE*cosTheta;
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G4double E_dom = sqrt(photonEnergy0*photonEnergy0 + photonE*photonE -2*photonEnergy0*photonE*cosTheta);
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G4double cosThetaE = E_num / E_dom;
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G4double sinThetaE = -sqrt((1. - cosThetaE) * (1. + cosThetaE));
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eDirX = sinThetaE * std::cos(phi);
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eDirY = sinThetaE * std::sin(phi);
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eDirZ = cosThetaE;
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G4ThreeVector eDirection(eDirX,eDirY,eDirZ);
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eDirection.rotateUz(photonDirection0);
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G4DynamicParticle* dp = new G4DynamicParticle (G4Electron::Electron(),
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eDirection,eKineticEnergy) ;
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fvect->push_back(dp);
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}
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// Revert to original if maximum number of iterations threshold has been reached
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if (iteration >= maxDopplerIterations)
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{
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photonE = photonEoriginal;
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bindingE = 0.;
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}
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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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fParticleChange->ProposeMomentumDirection(photonDirection1) ;
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G4double photonEnergy1 = photonE;
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if (photonEnergy1 > 0.)
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{
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fParticleChange->SetProposedKineticEnergy(photonEnergy1) ;
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if (iteration < maxDopplerIterations)
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{
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G4ThreeVector eDirection(eDirX,eDirY,eDirZ);
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eDirection.rotateUz(photonDirection0);
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G4DynamicParticle* dp = new G4DynamicParticle (G4Electron::Electron(),
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eDirection,eKineticEnergy) ;
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fvect->push_back(dp);
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}
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}
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else
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{
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photonEnergy1 = 0.;
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fParticleChange->SetProposedKineticEnergy(0.) ;
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fParticleChange->ProposeTrackStatus(fStopAndKill);
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}
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// sample deexcitation
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//
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if(fAtomDeexcitation && iteration < maxDopplerIterations) {
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G4int index = couple->GetIndex();
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if(fAtomDeexcitation->CheckDeexcitationActiveRegion(index)) {
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size_t nbefore = fvect->size();
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G4AtomicShellEnumerator as = G4AtomicShellEnumerator(shellIdx);
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const G4AtomicShell* shell = fAtomDeexcitation->GetAtomicShell(Z, as);
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fAtomDeexcitation->GenerateParticles(fvect, shell, Z, index);
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size_t nafter = fvect->size();
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if(nafter > nbefore) {
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for (size_t i=nbefore; i<nafter; ++i) {
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bindingE -= ((*fvect)[i])->GetKineticEnergy();
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}
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}
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}
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}
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if(bindingE < 0.0) { bindingE = 0.0; }
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fParticleChange->ProposeLocalEnergyDeposit(bindingE);
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}
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