Gabriele Cosmo
459 lines
16 KiB
C++
459 lines
16 KiB
C++
// This code implementation is the intellectual property of
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// the 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: G4eIonisation.cc,v 1.3.8.1.2.2 1999/12/10 15:42:00 gunter Exp $
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// GEANT4 tag $Name: geant4-01-01 $
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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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//
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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: based on object model of
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// 2nd December 1995, G.Cosmo
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// ---------- G4eIonisation physics process -----------
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// by Laszlo Urban, 20 March 1997
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// **************************************************************
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// It is the first implementation of the NEW IONISATION PROCESS.
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// It calculates the ionisation of e+/e-.
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// **************************************************************
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//
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// 07-04-98: remove 'tracking cut' of the ionizing particle, MMa
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// 04-09-98: new methods SetBining() PrintInfo()
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// 07-09-98: Cleanup
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// 02/02/99: correction inDoIt , L.Urban
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// --------------------------------------------------------------
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#include "G4eIonisation.hh"
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#include "G4EnergyLossTables.hh"
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#include "G4ios.hh"
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#include "G4UnitsTable.hh"
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// constructor and destructor
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G4eIonisation::G4eIonisation(const G4String& processName)
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: G4eEnergyLoss(processName),
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theMeanFreePathTable(NULL),
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LowestKineticEnergy(1.*keV),
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HighestKineticEnergy(100.*TeV),
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TotBin(100)
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{ }
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4eIonisation::~G4eIonisation()
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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 G4eIonisation::SetPhysicsTableBining(G4double lowE, G4double highE, G4int nBins)
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{
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LowestKineticEnergy = lowE; HighestKineticEnergy = highE; TotBin = nBins;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eIonisation::BuildPhysicsTable(const G4ParticleDefinition& aParticleType)
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// just call BuildLossTable+BuildLambdaTable
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{
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BuildLossTable(aParticleType) ;
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if(&aParticleType==G4Electron::Electron())
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{
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RecorderOfElectronProcess[CounterOfElectronProcess] = (*this).theLossTable ;
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CounterOfElectronProcess++;
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}
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else
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{
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RecorderOfPositronProcess[CounterOfPositronProcess] = (*this).theLossTable ;
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CounterOfPositronProcess++;
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}
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BuildLambdaTable(aParticleType) ;
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BuildDEDXTable(aParticleType) ;
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if(&aParticleType==G4Electron::Electron())
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PrintInfoDefinition();
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eIonisation::BuildLossTable(const G4ParticleDefinition& aParticleType)
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{
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// Build tables for the ionization energy loss
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// the tables are built for *MATERIALS*
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const G4double twoln10 = 2.*log(10.);
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const G4double Factor = twopi_mc2_rcl2;
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G4double LowEdgeEnergy, ionloss;
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// material properties
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G4double ElectronDensity,Eexc,Eexcm2,Cden,Mden,Aden,X0den,X1den ;
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// some local variables
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G4double tau,Tmax,gamma,gamma2,bg2,beta2,d,d2,d3,d4,delta,x,y ;
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ParticleMass = aParticleType.GetPDGMass();
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G4double* ParticleCutInKineticEnergy = aParticleType.GetEnergyCuts() ;
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// create table
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const G4MaterialTable* theMaterialTable = G4Material::GetMaterialTable();
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G4int numOfMaterials = theMaterialTable->length();
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if (theLossTable) { theLossTable->clearAndDestroy();
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delete theLossTable;
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}
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theLossTable = new G4PhysicsTable(numOfMaterials);
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// loop for materials
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for (G4int J=0; J<numOfMaterials; J++)
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{
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// create physics vector and fill it
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G4PhysicsLogVector* aVector = new G4PhysicsLogVector(
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LowestKineticEnergy, HighestKineticEnergy, TotBin);
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// get material parameters needed for the energy loss calculation
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const G4Material* material= (*theMaterialTable)[J];
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ElectronDensity = material->GetElectronDensity();
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Eexc = material->GetIonisation()->GetMeanExcitationEnergy();
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Eexc /= ParticleMass; Eexcm2 = Eexc*Eexc;
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Cden = material->GetIonisation()->GetCdensity();
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Mden = material->GetIonisation()->GetMdensity();
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Aden = material->GetIonisation()->GetAdensity();
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X0den = material->GetIonisation()->GetX0density();
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X1den = material->GetIonisation()->GetX1density();
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// now comes the loop for the kinetic energy values
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for (G4int i = 0 ; i < TotBin ; i++)
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{
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LowEdgeEnergy = aVector->GetLowEdgeEnergy(i) ;
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tau = LowEdgeEnergy/ParticleMass ;
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// Seltzer-Berger formula
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gamma = tau + 1.; gamma2 = gamma*gamma;
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bg2 = tau*(tau+2.);
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beta2 = bg2/gamma2;
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// electron
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if (&aParticleType==G4Electron::Electron())
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{
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Tmax = LowEdgeEnergy/2.;
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d = G4std::min(ParticleCutInKineticEnergy[J], Tmax)/ParticleMass;
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ionloss = log(2.*(tau+2.)/Eexcm2)-1.-beta2
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+ log((tau-d)*d)+tau/(tau-d)
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+ (0.5*d*d+(2.*tau+1.)*log(1.-d/tau))/gamma2;
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}
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else //positron
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{
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Tmax = LowEdgeEnergy ;
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d = G4std::min(ParticleCutInKineticEnergy[J], Tmax)/ParticleMass;
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d2=d*d/2.; d3=d*d*d/3.; d4=d*d*d*d/4.;
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y=1./(1.+gamma);
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ionloss = log(2.*(tau+2.)/Eexcm2)+log(tau*d)
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- beta2*(tau+2.*d-y*(3.*d2+y*(d-d3+y*(d2-tau*d3+d4))))/tau;
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}
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//density correction
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x = log(bg2)/twoln10;
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if (x < X0den) delta = 0.;
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else { delta = twoln10*x - Cden;
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if (x < X1den) delta += Aden*pow((X1den-x),Mden);
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}
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//now you can compute the total ionization loss
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ionloss -= delta ;
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ionloss *= Factor*ElectronDensity/beta2 ;
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if (ionloss <= 0.) ionloss = 0.;
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aVector->PutValue(i,ionloss) ;
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}
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theLossTable->insert(aVector);
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}
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eIonisation::BuildLambdaTable(const G4ParticleDefinition& aParticleType)
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{
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// Build mean free path tables for the delta ray production process
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// tables are built for MATERIALS
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G4double LowEdgeEnergy, Value, SIGMA;
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//create table
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const G4MaterialTable* theMaterialTable=G4Material::GetMaterialTable();
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G4int numOfMaterials = theMaterialTable->length();
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if (theMeanFreePathTable) { theMeanFreePathTable->clearAndDestroy();
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delete theMeanFreePathTable;
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}
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theMeanFreePathTable = new G4PhysicsTable(numOfMaterials);
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// get electron cuts in kinetic energy
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G4double* DeltaCutInKineticEnergy = G4Electron::Electron()->GetCutsInEnergy() ;
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// loop for materials
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for (G4int J=0 ; J < numOfMaterials; J++)
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{
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//create physics vector then fill it ....
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G4PhysicsLogVector* aVector = new G4PhysicsLogVector(
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LowestKineticEnergy, HighestKineticEnergy, TotBin);
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// compute the (macroscopic) cross section first
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const G4Material* material= (*theMaterialTable)[J];
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const
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G4ElementVector* theElementVector = material->GetElementVector();
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const
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G4double* theAtomicNumDensityVector = material->GetAtomicNumDensityVector();
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const
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G4int NumberOfElements = material->GetNumberOfElements() ;
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// get the electron kinetic energy cut for the actual material,
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// it will be used in ComputeMicroscopicCrossSection
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// (--> it will be the same for all the elements in this material )
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G4double DeltaThreshold = DeltaCutInKineticEnergy[J] ;
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for (G4int i = 0 ; i < TotBin ; i++)
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{
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LowEdgeEnergy = aVector->GetLowEdgeEnergy(i) ;
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SIGMA = 0.;
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for (G4int iel=0; iel<NumberOfElements; iel++ )
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{
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SIGMA += theAtomicNumDensityVector[iel]*
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ComputeMicroscopicCrossSection( aParticleType,
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LowEdgeEnergy,
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(*theElementVector)(iel)->GetZ(),
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DeltaThreshold);
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}
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// mean free path = 1./macroscopic cross section
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Value = SIGMA > DBL_MIN ? 1./SIGMA : DBL_MAX;
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aVector->PutValue(i, Value) ;
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}
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theMeanFreePathTable->insert(aVector);
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}
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4eIonisation::ComputeMicroscopicCrossSection(
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const G4ParticleDefinition& aParticleType,
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G4double KineticEnergy,
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G4double AtomicNumber ,
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G4double DeltaThreshold)
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{
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// calculates the microscopic cross section
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//(it is called for elements , AtomicNumber = Z )
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G4double MaxKineticEnergyTransfer, TotalCrossSection(0.);
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ParticleMass = aParticleType.GetPDGMass();
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G4double TotalEnergy = KineticEnergy + ParticleMass;
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G4double betasquare = KineticEnergy*(TotalEnergy+ParticleMass)
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/(TotalEnergy*TotalEnergy);
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G4double gamma = TotalEnergy/ParticleMass, gamma2 = gamma*gamma;
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G4double x=DeltaThreshold/KineticEnergy, x2 = x*x;
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if (&aParticleType==G4Electron::Electron())
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MaxKineticEnergyTransfer = 0.5*KineticEnergy;
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else MaxKineticEnergyTransfer = KineticEnergy;
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// now you can calculate the total cross section
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if (MaxKineticEnergyTransfer > DeltaThreshold)
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{
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if (&aParticleType==G4Electron::Electron()) //Moller (e-e-) scattering
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{
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TotalCrossSection = (gamma-1.)*(gamma-1.)*(0.5-x)/gamma2 + 1./x
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- 1./(1.-x)-(2.*gamma-1.)*log((1.-x)/x)/gamma2;
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TotalCrossSection /= betasquare;
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}
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else //Bhabha (e+e-) scattering
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{
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G4double y=1./(1.+gamma), y2 =y*y, y12=1.-2.*y;
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G4double b1=2.-y2, b2=y12*(3.+y2), b4=y12*y12*y12, b3=b4+y12*y12;
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TotalCrossSection = (1./x-1.)/betasquare+b1*log(x)+b2*(1.-x)
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- b3*(1.-x2)/2.+b4*(1.-x2*x)/3.;
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}
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TotalCrossSection *= (twopi_mc2_rcl2*AtomicNumber/KineticEnergy);
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}
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return TotalCrossSection ;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4VParticleChange* G4eIonisation::PostStepDoIt( const G4Track& trackData,
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const G4Step& stepData)
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{
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aParticleChange.Initialize(trackData) ;
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G4Material* aMaterial = trackData.GetMaterial() ;
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const G4DynamicParticle* aParticle = trackData.GetDynamicParticle() ;
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ParticleMass = aParticle->GetDefinition()->GetPDGMass();
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G4double KineticEnergy = aParticle->GetKineticEnergy();
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G4double TotalEnergy = KineticEnergy + ParticleMass;
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G4double Psquare = KineticEnergy*(TotalEnergy+ParticleMass);
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G4double TotalMomentum = sqrt(Psquare);
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G4double Esquare=TotalEnergy*TotalEnergy;
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G4ParticleMomentum ParticleDirection = aParticle->GetMomentumDirection();
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// get kinetic energy cut for the electron
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G4double* DeltaCutInKineticEnergy = G4Electron::Electron()->GetCutsInEnergy() ;
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G4double DeltaThreshold = DeltaCutInKineticEnergy[aMaterial->GetIndex()];
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// some kinematics
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G4double MaxKineticEnergyTransfer;
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if (Charge < 0.) MaxKineticEnergyTransfer = 0.5*KineticEnergy;
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else MaxKineticEnergyTransfer = KineticEnergy;
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// sampling kinetic energy of the delta ray
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if (MaxKineticEnergyTransfer <= DeltaThreshold) // pathological case (should not happen,
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// there is no change at all)
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return G4VContinuousDiscreteProcess::PostStepDoIt(trackData,stepData);
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// normal case
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G4double cc,y,y2,c2,b0,b1,b2,b3,b4,x,x1,grej,grejc;
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G4double tau = KineticEnergy/ParticleMass;
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G4double gamma = tau+1., gamma2=gamma*gamma;
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G4double xc = DeltaThreshold/KineticEnergy, xc1=1.-xc;
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if (Charge < 0.) // Moller (e-e-) scattering
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{
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b1=4./(9.*gamma2-10.*gamma+5.);
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b2=tau*tau*b1; b3=(2.*gamma2+2.*gamma-1.)*b1;
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cc=1.-2.*xc;
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do {
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x = xc/(1.-cc*G4UniformRand()); x1 = 1.-x;
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grej = b2*x*x-b3*x/x1+b1*gamma2/(x1*x1);
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} while (G4UniformRand()>grej) ;
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}
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else // Bhabha (e+e-) scattering
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{
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y=1./(gamma+1.); y2=y*y; cc=1.-2.*y;
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b1=2.-y2; b2=cc*(3.+y2);
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c2=cc*cc; b4=c2*cc; b3=c2+b4;
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b0=gamma2/(gamma2-1.);
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grejc=(((b4*xc-b3)*xc+b2)*xc-b1)*xc+b0;
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do {
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x = xc/(1.-xc1*G4UniformRand());
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grej = ((((b4*x-b3)*x+b2)*x-b1)*x+b0)/grejc;
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} while (G4UniformRand()>grej);
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}
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G4double DeltaKineticEnergy = x * KineticEnergy;
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// protection :do not produce a secondary with 0. kinetic energy !
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if (DeltaKineticEnergy <= 0.)
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return G4VContinuousDiscreteProcess::PostStepDoIt(trackData,stepData);
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G4double DeltaTotalMomentum = sqrt(DeltaKineticEnergy * (DeltaKineticEnergy +
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2. * electron_mass_c2 ));
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G4double costheta = DeltaKineticEnergy * (TotalEnergy + electron_mass_c2)
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/(DeltaTotalMomentum * TotalMomentum);
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if (costheta < -1.) costheta = -1.;
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if (costheta > +1.) costheta = +1.;
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// direction of the delta electron
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G4double phi = twopi * G4UniformRand();
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G4double sintheta = sqrt((1.+costheta)*(1.-costheta));
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G4double dirx = sintheta * cos(phi), diry = sintheta * sin(phi), dirz = costheta;
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G4ThreeVector DeltaDirection(dirx,diry,dirz);
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DeltaDirection.rotateUz(ParticleDirection);
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// create G4DynamicParticle object for delta ray
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G4DynamicParticle* theDeltaRay = new G4DynamicParticle;
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theDeltaRay->SetKineticEnergy( DeltaKineticEnergy );
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theDeltaRay->SetMomentumDirection(
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DeltaDirection.x(),DeltaDirection.y(),DeltaDirection.z());
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theDeltaRay->SetDefinition(G4Electron::Electron());
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// fill aParticleChange
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// changed energy and momentum of the actual particle
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G4double finalKineticEnergy = KineticEnergy - DeltaKineticEnergy;
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G4double Edep = 0. ;
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if (finalKineticEnergy > MinKineticEnergy)
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{
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G4double finalPx = TotalMomentum*ParticleDirection.x()
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- DeltaTotalMomentum*DeltaDirection.x();
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G4double finalPy = TotalMomentum*ParticleDirection.y()
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- DeltaTotalMomentum*DeltaDirection.y();
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G4double finalPz = TotalMomentum*ParticleDirection.z()
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- DeltaTotalMomentum*DeltaDirection.z();
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G4double finalMomentum =
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sqrt(finalPx*finalPx+finalPy*finalPy+finalPz*finalPz) ;
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finalPx /= finalMomentum ;
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finalPy /= finalMomentum ;
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finalPz /= finalMomentum ;
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aParticleChange.SetMomentumChange( finalPx,finalPy,finalPz );
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}
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else
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{
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finalKineticEnergy = 0.;
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Edep = finalKineticEnergy ;
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if (Charge < 0.) aParticleChange.SetStatusChange(fStopAndKill);
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else aParticleChange.SetStatusChange(fStopButAlive);
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}
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aParticleChange.SetEnergyChange( finalKineticEnergy );
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aParticleChange.SetNumberOfSecondaries(1);
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aParticleChange.AddSecondary( theDeltaRay );
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aParticleChange.SetLocalEnergyDeposit (Edep);
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return G4VContinuousDiscreteProcess::PostStepDoIt(trackData,stepData);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eIonisation::PrintInfoDefinition()
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{
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G4String comments = "delta cross sections from Moller+Bhabha. ";
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comments += "Good description from 1 KeV to 100 GeV.\n";
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comments += " delta ray energy sampled from differential Xsection.";
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G4cout << G4endl << GetProcessName() << ": " << comments
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<< "\n PhysicsTables from " << G4BestUnit(LowestKineticEnergy,"Energy")
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<< " to " << G4BestUnit(HighestKineticEnergy,"Energy")
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<< " in " << TotBin << " bins. \n";
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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