| 1 | //
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| 2 | // ********************************************************************
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| 3 | // * License and Disclaimer *
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| 4 | // * *
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| 5 | // * The Geant4 software is copyright of the Copyright Holders of *
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| 6 | // * the Geant4 Collaboration. It is provided under the terms and *
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| 7 | // * conditions of the Geant4 Software License, included in the file *
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| 8 | // * LICENSE and available at http://cern.ch/geant4/license . These *
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| 9 | // * include a list of copyright holders. *
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| 10 | // * *
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| 11 | // * Neither the authors of this software system, nor their employing *
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| 12 | // * institutes,nor the agencies providing financial support for this *
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| 13 | // * work make any representation or warranty, express or implied, *
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| 14 | // * regarding this software system or assume any liability for its *
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| 15 | // * use. Please see the license in the file LICENSE and URL above *
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| 16 | // * for the full disclaimer and the limitation of liability. *
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| 17 | // * *
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| 18 | // * This code implementation is the result of the scientific and *
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| 19 | // * technical work of the GEANT4 collaboration. *
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| 20 | // * By using, copying, modifying or distributing the software (or *
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| 21 | // * any work based on the software) you agree to acknowledge its *
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| 22 | // * use in resulting scientific publications, and indicate your *
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| 23 | // * acceptance of all terms of the Geant4 Software license. *
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| 24 | // ********************************************************************
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| 25 | //
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| 26 | // $Id: G4LowEnergyCompton.cc,v 1.41 2006/06/29 19:40:15 gunter Exp $
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| 27 | // GEANT4 tag $Name: geant4-09-01-patch-02 $
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| 28 | //
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| 29 | // Author: A. Forti
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| 30 | // Maria Grazia Pia (Maria.Grazia.Pia@cern.ch)
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| 31 | //
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| 32 | // History:
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| 33 | // --------
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| 34 | // Added Livermore data table construction methods A. Forti
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| 35 | // Modified BuildMeanFreePath to read new data tables A. Forti
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| 36 | // Modified PostStepDoIt to insert sampling with EPDL97 data A. Forti
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| 37 | // Added SelectRandomAtom A. Forti
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| 38 | // Added map of the elements A. Forti
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| 39 | // 24.04.2001 V.Ivanchenko - Remove RogueWave
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| 40 | // 06.08.2001 MGP - Revised according to a design iteration
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| 41 | // 22.01.2003 V.Ivanchenko - Cut per region
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| 42 | // 10.03.2003 V.Ivanchenko - Remove CutPerMaterial warning
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| 43 | // 24.04.2003 V.Ivanchenko - Cut per region mfpt
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| 44 | //
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| 45 | // -------------------------------------------------------------------
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| 46 |
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| 47 | #include "G4LowEnergyCompton.hh"
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| 48 | #include "Randomize.hh"
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| 49 | #include "G4ParticleDefinition.hh"
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| 50 | #include "G4Track.hh"
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| 51 | #include "G4Step.hh"
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| 52 | #include "G4ForceCondition.hh"
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| 53 | #include "G4Gamma.hh"
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| 54 | #include "G4Electron.hh"
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| 55 | #include "G4DynamicParticle.hh"
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| 56 | #include "G4VParticleChange.hh"
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| 57 | #include "G4ThreeVector.hh"
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| 58 | #include "G4EnergyLossTables.hh"
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| 59 | #include "G4VCrossSectionHandler.hh"
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| 60 | #include "G4CrossSectionHandler.hh"
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| 61 | #include "G4VEMDataSet.hh"
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| 62 | #include "G4CompositeEMDataSet.hh"
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| 63 | #include "G4VDataSetAlgorithm.hh"
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| 64 | #include "G4LogLogInterpolation.hh"
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| 65 | #include "G4VRangeTest.hh"
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| 66 | #include "G4RangeTest.hh"
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| 67 | #include "G4MaterialCutsCouple.hh"
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| 68 |
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| 69 |
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| 70 | G4LowEnergyCompton::G4LowEnergyCompton(const G4String& processName)
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| 71 | : G4VDiscreteProcess(processName),
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| 72 | lowEnergyLimit(250*eV),
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| 73 | highEnergyLimit(100*GeV),
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| 74 | intrinsicLowEnergyLimit(10*eV),
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| 75 | intrinsicHighEnergyLimit(100*GeV)
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| 76 | {
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| 77 | if (lowEnergyLimit < intrinsicLowEnergyLimit ||
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| 78 | highEnergyLimit > intrinsicHighEnergyLimit)
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| 79 | {
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| 80 | G4Exception("G4LowEnergyCompton::G4LowEnergyCompton - energy outside intrinsic process validity range");
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| 81 | }
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| 82 |
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| 83 | crossSectionHandler = new G4CrossSectionHandler;
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| 84 |
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| 85 | G4VDataSetAlgorithm* scatterInterpolation = new G4LogLogInterpolation;
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| 86 | G4String scatterFile = "comp/ce-sf-";
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| 87 | scatterFunctionData = new G4CompositeEMDataSet(scatterInterpolation, 1., 1.);
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| 88 | scatterFunctionData->LoadData(scatterFile);
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| 89 |
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| 90 | meanFreePathTable = 0;
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| 91 |
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| 92 | rangeTest = new G4RangeTest;
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| 93 |
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| 94 | if (verboseLevel > 0)
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| 95 | {
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| 96 | G4cout << GetProcessName() << " is created " << G4endl
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| 97 | << "Energy range: "
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| 98 | << lowEnergyLimit / keV << " keV - "
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| 99 | << highEnergyLimit / GeV << " GeV"
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| 100 | << G4endl;
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| 101 | }
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| 102 | }
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| 103 |
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| 104 | G4LowEnergyCompton::~G4LowEnergyCompton()
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| 105 | {
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| 106 | delete meanFreePathTable;
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| 107 | delete crossSectionHandler;
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| 108 | delete scatterFunctionData;
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| 109 | delete rangeTest;
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| 110 | }
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| 111 |
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| 112 | void G4LowEnergyCompton::BuildPhysicsTable(const G4ParticleDefinition& )
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| 113 | {
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| 114 |
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| 115 | crossSectionHandler->Clear();
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| 116 | G4String crossSectionFile = "comp/ce-cs-";
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| 117 | crossSectionHandler->LoadData(crossSectionFile);
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| 118 |
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| 119 | delete meanFreePathTable;
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| 120 | meanFreePathTable = crossSectionHandler->BuildMeanFreePathForMaterials();
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| 121 | }
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| 122 |
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| 123 | G4VParticleChange* G4LowEnergyCompton::PostStepDoIt(const G4Track& aTrack,
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| 124 | const G4Step& aStep)
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| 125 | {
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| 126 | // The scattered gamma energy is sampled according to Klein - Nishina formula.
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| 127 | // then accepted or rejected depending on the Scattering Function multiplied
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| 128 | // by factor from Klein - Nishina formula.
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| 129 | // Expression of the angular distribution as Klein Nishina
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| 130 | // angular and energy distribution and Scattering fuctions is taken from
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| 131 | // D. E. Cullen "A simple model of photon transport" Nucl. Instr. Meth.
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| 132 | // Phys. Res. B 101 (1995). Method of sampling with form factors is different
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| 133 | // data are interpolated while in the article they are fitted.
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| 134 | // Reference to the article is from J. Stepanek New Photon, Positron
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| 135 | // and Electron Interaction Data for GEANT in Energy Range from 1 eV to 10
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| 136 | // TeV (draft).
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| 137 | // The random number techniques of Butcher & Messel are used
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| 138 | // (Nucl Phys 20(1960),15).
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| 139 |
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| 140 | aParticleChange.Initialize(aTrack);
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| 141 |
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| 142 | // Dynamic particle quantities
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| 143 | const G4DynamicParticle* incidentPhoton = aTrack.GetDynamicParticle();
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| 144 | G4double photonEnergy0 = incidentPhoton->GetKineticEnergy();
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| 145 |
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| 146 | if (photonEnergy0 <= lowEnergyLimit)
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| 147 | {
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| 148 | aParticleChange.ProposeTrackStatus(fStopAndKill);
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| 149 | aParticleChange.ProposeEnergy(0.);
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| 150 | aParticleChange.ProposeLocalEnergyDeposit(photonEnergy0);
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| 151 | return G4VDiscreteProcess::PostStepDoIt(aTrack,aStep);
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| 152 | }
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| 153 |
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| 154 | G4double e0m = photonEnergy0 / electron_mass_c2 ;
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| 155 | G4ParticleMomentum photonDirection0 = incidentPhoton->GetMomentumDirection();
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| 156 |
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| 157 | // Select randomly one element in the current material
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| 158 | const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple();
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| 159 | G4int Z = crossSectionHandler->SelectRandomAtom(couple,photonEnergy0);
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| 160 |
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| 161 | G4double epsilon0 = 1. / (1. + 2. * e0m);
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| 162 | G4double epsilon0Sq = epsilon0 * epsilon0;
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| 163 | G4double alpha1 = -std::log(epsilon0);
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| 164 | G4double alpha2 = 0.5 * (1. - epsilon0Sq);
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| 165 |
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| 166 | G4double wlPhoton = h_Planck*c_light/photonEnergy0;
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| 167 |
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| 168 | // Sample the energy of the scattered photon
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| 169 | G4double epsilon;
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| 170 | G4double epsilonSq;
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| 171 | G4double oneCosT;
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| 172 | G4double sinT2;
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| 173 | G4double gReject;
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| 174 | do
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| 175 | {
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| 176 | if ( alpha1/(alpha1+alpha2) > G4UniformRand())
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| 177 | {
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| 178 | epsilon = std::exp(-alpha1 * G4UniformRand()); // std::pow(epsilon0,G4UniformRand())
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| 179 | epsilonSq = epsilon * epsilon;
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| 180 | }
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| 181 | else
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| 182 | {
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| 183 | epsilonSq = epsilon0Sq + (1. - epsilon0Sq) * G4UniformRand();
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| 184 | epsilon = std::sqrt(epsilonSq);
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| 185 | }
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| 186 |
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| 187 | oneCosT = (1. - epsilon) / ( epsilon * e0m);
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| 188 | sinT2 = oneCosT * (2. - oneCosT);
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| 189 | G4double x = std::sqrt(oneCosT/2.) / (wlPhoton/cm);
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| 190 | G4double scatteringFunction = scatterFunctionData->FindValue(x,Z-1);
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| 191 | gReject = (1. - epsilon * sinT2 / (1. + epsilonSq)) * scatteringFunction;
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| 192 |
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| 193 | } while(gReject < G4UniformRand()*Z);
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| 194 |
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| 195 | G4double cosTheta = 1. - oneCosT;
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| 196 | G4double sinTheta = std::sqrt (sinT2);
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| 197 | G4double phi = twopi * G4UniformRand() ;
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| 198 | G4double dirx = sinTheta * std::cos(phi);
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| 199 | G4double diry = sinTheta * std::sin(phi);
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| 200 | G4double dirz = cosTheta ;
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| 201 |
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| 202 | // Update G4VParticleChange for the scattered photon
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| 203 |
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| 204 | G4ThreeVector photonDirection1(dirx,diry,dirz);
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| 205 | photonDirection1.rotateUz(photonDirection0);
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| 206 | aParticleChange.ProposeMomentumDirection(photonDirection1) ;
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| 207 | G4double photonEnergy1 = epsilon * photonEnergy0;
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| 208 |
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| 209 | if (photonEnergy1 > 0.)
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| 210 | {
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| 211 | aParticleChange.ProposeEnergy(photonEnergy1) ;
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| 212 | }
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| 213 | else
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| 214 | {
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| 215 | aParticleChange.ProposeEnergy(0.) ;
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| 216 | aParticleChange.ProposeTrackStatus(fStopAndKill);
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| 217 | }
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| 218 |
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| 219 | // Kinematics of the scattered electron
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| 220 | G4double eKineticEnergy = photonEnergy0 - photonEnergy1;
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| 221 |
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| 222 | // Generate the electron only if with large enough range w.r.t. cuts and safety
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| 223 |
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| 224 | G4double safety = aStep.GetPostStepPoint()->GetSafety();
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| 225 |
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| 226 | if (rangeTest->Escape(G4Electron::Electron(),couple,eKineticEnergy,safety))
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| 227 | {
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| 228 | G4double eMomentum = std::sqrt(eKineticEnergy*(eKineticEnergy+2.*electron_mass_c2));
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| 229 | G4ThreeVector eDirection((photonEnergy0 * photonDirection0 -
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| 230 | photonEnergy1 * photonDirection1) * (1./eMomentum));
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| 231 | G4DynamicParticle* electron = new G4DynamicParticle (G4Electron::Electron(),
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| 232 | eDirection,eKineticEnergy) ;
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| 233 | aParticleChange.SetNumberOfSecondaries(1);
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| 234 | aParticleChange.AddSecondary(electron);
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| 235 | aParticleChange.ProposeLocalEnergyDeposit(0.);
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| 236 | }
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| 237 | else
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| 238 | {
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| 239 | aParticleChange.SetNumberOfSecondaries(0);
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| 240 | aParticleChange.ProposeLocalEnergyDeposit(eKineticEnergy);
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| 241 | }
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| 242 |
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| 243 | return G4VDiscreteProcess::PostStepDoIt( aTrack, aStep);
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| 244 | }
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| 245 |
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| 246 | G4bool G4LowEnergyCompton::IsApplicable(const G4ParticleDefinition& particle)
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| 247 | {
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| 248 | return ( &particle == G4Gamma::Gamma() );
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| 249 | }
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| 250 |
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| 251 | G4double G4LowEnergyCompton::GetMeanFreePath(const G4Track& track,
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| 252 | G4double, // previousStepSize
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| 253 | G4ForceCondition*)
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| 254 | {
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| 255 | const G4DynamicParticle* photon = track.GetDynamicParticle();
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| 256 | G4double energy = photon->GetKineticEnergy();
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| 257 | const G4MaterialCutsCouple* couple = track.GetMaterialCutsCouple();
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| 258 | size_t materialIndex = couple->GetIndex();
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| 259 |
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| 260 | G4double meanFreePath;
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| 261 | if (energy > highEnergyLimit) meanFreePath = meanFreePathTable->FindValue(highEnergyLimit,materialIndex);
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| 262 | else if (energy < lowEnergyLimit) meanFreePath = DBL_MAX;
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| 263 | else meanFreePath = meanFreePathTable->FindValue(energy,materialIndex);
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| 264 | return meanFreePath;
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| 265 | }
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