Gabriele Cosmo
262 lines
9.3 KiB
C++
262 lines
9.3 KiB
C++
//
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// ********************************************************************
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// * DISCLAIMER *
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// * *
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// * The following disclaimer summarizes all the specific disclaimers *
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// * of contributors to this software. The specific disclaimers,which *
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// * govern, are listed with their locations in: *
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// * http://cern.ch/geant4/license *
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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. *
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// * *
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// * This code implementation is the intellectual property of the *
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// * GEANT4 collaboration. *
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// * By copying, distributing or modifying the Program (or any work *
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// * based on the Program) you indicate your acceptance of this *
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// * statement, and all its terms. *
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// ********************************************************************
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//
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// $Id: G4LowEnergyCompton.cc,v 1.33 2001/11/07 20:47:29 pia Exp $
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// GEANT4 tag $Name: geant4-05-00 $
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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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//
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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 "G4CutsPerMaterialWarning.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(scatterFile,scatterInterpolation,1.,1.);
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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& photon)
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{
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G4CutsPerMaterialWarning warning;
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warning.PrintWarning(&photon);
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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.SetStatusChange(fStopAndKill);
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aParticleChange.SetEnergyChange(0.);
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aParticleChange.SetLocalEnergyDeposit(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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G4Material* material = aTrack.GetMaterial();
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G4int Z = crossSectionHandler->SelectRandomAtom(material,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 = -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 = exp(-alpha1 * G4UniformRand()); // 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 = 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 = 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 = sqrt (sinT2);
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G4double phi = twopi * G4UniformRand() ;
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G4double dirx = sinTheta * cos(phi);
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G4double diry = sinTheta * 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.SetMomentumChange(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.SetEnergyChange(photonEnergy1) ;
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}
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else
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{
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aParticleChange.SetEnergyChange(0.) ;
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aParticleChange.SetStatusChange(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(),material,eKineticEnergy,safety))
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{
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G4double eMomentum = 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.SetLocalEnergyDeposit(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.SetLocalEnergyDeposit(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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G4Material* material = track.GetMaterial();
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size_t materialIndex = material->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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