Import Geant4 0.0.0 source tree
This commit is contained in:
Gabriele Cosmo
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// This code implementation is the intellectual property of
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// the RD44 GEANT4 collaboration.
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//
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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 statement,
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// and all its terms.
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//
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// $Id: G4eplusAnnihilation.cc,v 2.8 1998/11/13 13:41:58 maire Exp $
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// GEANT4 tag $Name: geant4-00 $
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//
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//
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// --------------------------------------------------------------
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// GEANT 4 class implementation file
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// CERN Geneva Switzerland
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//
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// For information related to this code contact:
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// CERN, IT Division, ASD group
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// History: first implementation, based on object model of
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// 2nd December 1995, G.Cosmo
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// ------------ G4eplusAnnihilation process --------
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// by Michel Maire, 7 July 1996
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// **************************************************************
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// 10-01-97, crossection table + mean free path table, M.Maire
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// 17-03-97, merge 'in fly' and 'at rest', M.Maire
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// 23-03-97, protection in BuildPhysicsTable, M.Maire
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// 31-08-98, new methods SetBining() and PrintInfo()
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// --------------------------------------------------------------
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#include "G4eplusAnnihilation.hh"
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#include "G4UnitsTable.hh"
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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// constructor
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G4eplusAnnihilation::G4eplusAnnihilation(const G4String& processName)
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: G4VRestDiscreteProcess (processName),
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theCrossSectionTable(NULL),
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theMeanFreePathTable(NULL),
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LowestEnergyLimit ( 10*keV), // initialization
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HighestEnergyLimit( 10*TeV),
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NumbBinTable(100)
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{ }
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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// destructor
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G4eplusAnnihilation::~G4eplusAnnihilation()
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{
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if (theCrossSectionTable) {
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theCrossSectionTable->clearAndDestroy();
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delete theCrossSectionTable;
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}
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if (theMeanFreePathTable) {
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theMeanFreePathTable->clearAndDestroy();
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delete theMeanFreePathTable;
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}
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eplusAnnihilation::SetPhysicsTableBining(G4double lowE, G4double highE, G4int nBins)
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{
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LowestEnergyLimit = lowE; HighestEnergyLimit = highE; NumbBinTable = nBins;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eplusAnnihilation::BuildPhysicsTable(const G4ParticleDefinition& PositronType)
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// Build microscopic total cross section tables and mean free path table
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{
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G4double LowEdgeEnergy, Value;
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G4PhysicsLogVector* ptrVector;
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// Build microscopic cross section tables for the e+e- annihilation
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if (theCrossSectionTable) {
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theCrossSectionTable->clearAndDestroy(); delete theCrossSectionTable; }
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theCrossSectionTable = new G4PhysicsTable( G4Element::GetNumberOfElements()) ;
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const G4ElementTable* theElementTable = G4Element::GetElementTable() ;
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G4double AtomicNumber;
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G4int J;
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for ( J=0 ; J < G4Element::GetNumberOfElements(); J++ )
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{
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//create physics vector then fill it ....
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ptrVector = new G4PhysicsLogVector(LowestEnergyLimit, HighestEnergyLimit,
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NumbBinTable ) ;
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AtomicNumber = (*theElementTable)(J)->GetZ();
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for ( G4int i = 0 ; i < NumbBinTable ; i++ )
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{
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LowEdgeEnergy = ptrVector->GetLowEdgeEnergy( i ) ;
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Value = ComputeCrossSectionPerAtom( LowEdgeEnergy, AtomicNumber);
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ptrVector->PutValue( i , Value ) ;
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}
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theCrossSectionTable->insertAt( J , ptrVector ) ;
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}
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// Build mean free path table for the e+e- annihilation
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if (theMeanFreePathTable) {
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theMeanFreePathTable->clearAndDestroy(); delete theMeanFreePathTable; }
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theMeanFreePathTable = new G4PhysicsTable( G4Material::GetNumberOfMaterials() );
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const G4MaterialTable* theMaterialTable = G4Material::GetMaterialTable() ;
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G4Material* material;
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for ( J=0 ; J < G4Material::GetNumberOfMaterials(); J++ )
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{
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//create physics vector then fill it ....
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ptrVector = new G4PhysicsLogVector(LowestEnergyLimit, HighestEnergyLimit,
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NumbBinTable ) ;
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material = (*theMaterialTable)(J);
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for ( G4int i = 0 ; i < NumbBinTable ; i++ )
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{
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LowEdgeEnergy = ptrVector->GetLowEdgeEnergy( i ) ;
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Value = ComputeMeanFreePath( LowEdgeEnergy, material);
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ptrVector->PutValue( i , Value ) ;
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}
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theMeanFreePathTable->insertAt( J , ptrVector ) ;
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}
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PrintInfoDefinition();
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4eplusAnnihilation::ComputeCrossSectionPerAtom
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(G4double PositKinEnergy, G4double AtomicNumber)
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// Calculates the microscopic cross section of annihilation into two photons
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// from the Heilter formula.
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// GEANT4 internal units.
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{
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static const G4double pi_rcl2 = pi*classic_electr_radius*classic_electr_radius;
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G4double gama = 1. + PositKinEnergy/electron_mass_c2;
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G4double gama2 = gama*gama, sqgama2 = sqrt(gama2-1.);
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return pi_rcl2*AtomicNumber*((gama2+4*gama+1.)*log(gama+sqgama2) - (gama+3.)*sqgama2)
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/((gama2-1.)*(gama+1.));
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4VParticleChange* G4eplusAnnihilation::PostStepDoIt(const G4Track& aTrack,
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const G4Step& aStep)
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//
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// The secondaries Gamma energies are sampled using the Heitler cross section.
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//
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// A modified version of the random number techniques of Butcher & Messel is used
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// (Nuc Phys 20(1960),15).
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//
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// GEANT4 internal units.
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//
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// Note 1 : The initial electron is assumed free and at rest.
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//
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// Note 2 : The annihilation processes producing one or more than two photons are
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// ignored, as negligible compared to the two photons process.
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{
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aParticleChange.Initialize(aTrack);
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G4Material* aMaterial = aTrack.GetMaterial();
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const G4DynamicParticle* aDynamicPositron = aTrack.GetDynamicParticle();
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G4double PositKinEnergy = aDynamicPositron->GetKineticEnergy();
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G4ParticleMomentum PositDirection = aDynamicPositron->GetMomentumDirection();
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aParticleChange.Initialize(aTrack);
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// Do not make anything if PositKinEnergy=0. , the annihilation then
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// should be performed by the AtRestDoIt!
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if (PositKinEnergy == 0.) return &aParticleChange;
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G4double gama = 1. + PositKinEnergy/electron_mass_c2;
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G4double gamap1 = gama+1. , gamam1 = gama-1. , sqgrate = sqrt(gamam1/gamap1)/2. ,
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sqg2m1 = sqrt(gamam1*gamap1);
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// limits of the energy sampling
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G4double epsilmin = 0.5 - sqgrate , epsilmax = 0.5 + sqgrate;
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G4double epsilqot = epsilmax/epsilmin;
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//
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// sample the energy rate of the created gammas
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//
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G4double epsil, greject ;
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do {
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epsil = epsilmin*pow(epsilqot,G4UniformRand());
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greject = 1. - epsil + (2*gama*epsil-1.)/(epsil*gamap1*gamap1);
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} while( greject < G4UniformRand() );
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//
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// scattered Gamma angles. ( Z - axis along the parent positron)
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//
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G4double cost = (epsil*gamap1-1.)/(epsil*sqg2m1) , sint = sqrt((1.+cost)*(1.-cost));
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G4double phi = twopi * G4UniformRand() ;
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G4double dirx = sint*cos(phi) , diry = sint*sin(phi) , dirz = cost;
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//
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// kinematic of the created pair
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//
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G4double LocalEnerDeposit = 0. ;
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aParticleChange.SetNumberOfSecondaries(2) ;
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G4double TotalAvailableEnergy = PositKinEnergy + 2*electron_mass_c2;
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G4double Phot1Energy = epsil*TotalAvailableEnergy;
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G4double GammaCut= (G4Gamma::GetCutsInEnergy())[aMaterial->GetIndex()];
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if (Phot1Energy > GammaCut)
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{
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G4ThreeVector Phot1Direction ( dirx, diry, dirz );
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Phot1Direction.rotateUz(PositDirection);
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// create G4DynamicParticle object for the particle1
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G4DynamicParticle* aParticle1= new G4DynamicParticle (G4Gamma::Gamma(),
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Phot1Direction, Phot1Energy);
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aParticleChange.AddSecondary( aParticle1 ) ;
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}
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else
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{ LocalEnerDeposit += Phot1Energy; }
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G4double Phot2Energy =(1.-epsil)*TotalAvailableEnergy;
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if (Phot2Energy > GammaCut)
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{
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G4double Eratio = Phot1Energy/Phot2Energy;
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G4double PositP = sqrt(PositKinEnergy*(PositKinEnergy+2.*electron_mass_c2));
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G4ThreeVector Phot2Direction (-dirx*Eratio, -diry*Eratio,
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(PositP-dirz*Phot1Energy)/Phot2Energy);
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Phot2Direction.rotateUz(PositDirection);
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// create G4DynamicParticle object for the particle2
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G4DynamicParticle* aParticle2= new G4DynamicParticle (G4Gamma::Gamma(),
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Phot2Direction, Phot2Energy);
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aParticleChange.AddSecondary( aParticle2 ) ;
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}
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else
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{ LocalEnerDeposit += Phot2Energy; }
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aParticleChange.SetLocalEnergyDeposit( LocalEnerDeposit ) ;
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//
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// Kill the incident positron
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//
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aParticleChange.SetMomentumChange( 0., 0., 0. ) ;
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aParticleChange.SetEnergyChange( 0. ) ;
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aParticleChange.SetStatusChange( fStopAndKill ) ;
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return &aParticleChange;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4VParticleChange* G4eplusAnnihilation::AtRestDoIt(const G4Track& aTrack,
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const G4Step& aStep)
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//
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// Performs the e+ e- annihilation when both particles are assumed at rest.
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// It generates two back to back photons with energy = electron_mass.
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// The angular distribution is isotropic.
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// GEANT4 internal units
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//
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// Note : Effects due to binding of atomic electrons are negliged.
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{
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aParticleChange.Initialize(aTrack);
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G4Material* aMaterial = aTrack.GetMaterial();
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aParticleChange.SetNumberOfSecondaries(2) ;
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if (electron_mass_c2 > (G4Gamma::GetCutsInEnergy())[aMaterial->GetIndex()])
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{
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G4double cosTeta = 2*G4UniformRand()-1. , sinTeta = sqrt(1.-cosTeta*cosTeta);
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G4double Phi = twopi * G4UniformRand() ;
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G4ThreeVector Direction (sinTeta*cos(Phi), sinTeta*sin(Phi), cosTeta);
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aParticleChange.AddSecondary( new G4DynamicParticle (G4Gamma::Gamma(),
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Direction, electron_mass_c2) );
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aParticleChange.AddSecondary( new G4DynamicParticle (G4Gamma::Gamma(),
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-Direction, electron_mass_c2) );
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aParticleChange.SetLocalEnergyDeposit(0.);
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}
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else
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{ aParticleChange.SetLocalEnergyDeposit( 2*electron_mass_c2 ); }
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// Kill the incident positron
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//
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aParticleChange.SetStatusChange( fStopAndKill );
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return &aParticleChange;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eplusAnnihilation::PrintInfoDefinition()
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{
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G4String comments = "Total cross section from Heilter formula (annihilation into 2 photons).\n";
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comments += " gamma energies sampled according Heitler";
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G4cout << endl << GetProcessName() << ": " << comments
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<< "\n PhysicsTables from " << G4BestUnit(LowestEnergyLimit,"Energy")
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<< " to " << G4BestUnit(HighestEnergyLimit,"Energy")
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<< " in " << NumbBinTable << " bins. \n";
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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