Import Geant4 0.0.0 source tree
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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: G4ionIonisation.cc,v 2.1 1998/12/08 17:12:19 urban Exp $
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// GEANT4 tag $Name: geant4-00 $
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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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// ---------- G4ionIonisation physics process -----------
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// by Laszlo Urban, 08 Dec 1998
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// **************************************************************
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// It is the first implementation of the ionisation for IONS
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// --------------------------------------------------------------
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#include "G4ionIonisation.hh"
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#include "G4UnitsTable.hh"
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// constructor and destructor
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G4ionIonisation::G4ionIonisation(const G4String& processName)
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: G4hEnergyLoss(processName)
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{ PrintInfoDefinition() ; }
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G4ionIonisation::~G4ionIonisation()
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{ }
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G4double G4ionIonisation::GetMeanFreePath(
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const G4Track& trackData,
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G4double previousStepSize,
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G4ForceCondition* condition)
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{
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const G4DynamicParticle* aParticle ;
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G4Material* aMaterial ;
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G4double MeanFreePath;
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*condition = NotForced ;
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aParticle = trackData.GetDynamicParticle() ;
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aMaterial = trackData.GetMaterial() ;
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G4double KineticEnergy = aParticle->GetKineticEnergy() ;
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G4double ChargeSquare=(aParticle->GetDefinition()->GetPDGCharge())*
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(aParticle->GetDefinition()->GetPDGCharge());
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// compute the (macroscopic) cross section first
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const G4ElementVector* theElementVector=
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aMaterial->GetElementVector() ;
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const G4double* theAtomicNumDensityVector =
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aMaterial->GetAtomicNumDensityVector();
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const G4int NumberOfElements=
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aMaterial->GetNumberOfElements() ;
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G4int index = aMaterial->GetIndex() ;
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DeltaCutInKineticEnergy = G4Electron::Electron()->GetCutsInEnergy();
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DeltaCutInKineticEnergyNow = DeltaCutInKineticEnergy[index] ;
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G4double 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(aParticle,
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KineticEnergy,
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(*theElementVector)(iel)->GetZ() ) ;
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}
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sigma *= twopi_mc2_rcl2 * ChargeSquare ;
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// mean free path = 1./macroscopic cross section
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MeanFreePath = sigma<=0 ? DBL_MAX : 1./sigma ;
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return MeanFreePath ;
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}
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G4double G4ionIonisation::ComputeMicroscopicCrossSection(
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const G4DynamicParticle* aParticle,
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G4double KineticEnergy,
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G4double AtomicNumber)
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{
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G4double TotalEnergy,
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betasquare,
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MaxKineticEnergyTransfer,TotalCrossSection,tempvar;
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// get particle data ...................................
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ParticleMass = aParticle->GetDefinition()->GetPDGMass() ;
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TotalEnergy=KineticEnergy + ParticleMass;
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// some kinematics......................
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betasquare = KineticEnergy*(TotalEnergy+ParticleMass)
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/(TotalEnergy*TotalEnergy);
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tempvar = ParticleMass+electron_mass_c2;
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MaxKineticEnergyTransfer = 2.*electron_mass_c2*KineticEnergy
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*(TotalEnergy+ParticleMass)
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/(tempvar*tempvar+2.*electron_mass_c2*KineticEnergy);
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// now you can calculate the total cross section ------------------
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if( MaxKineticEnergyTransfer > DeltaCutInKineticEnergyNow )
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{
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tempvar=DeltaCutInKineticEnergyNow/MaxKineticEnergyTransfer;
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TotalCrossSection = (1.-tempvar*(1.-betasquare*log(tempvar)))
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/DeltaCutInKineticEnergyNow;
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TotalCrossSection *= AtomicNumber/betasquare;
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}
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else
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TotalCrossSection= 0. ;
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return TotalCrossSection ;
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}
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G4VParticleChange* G4ionIonisation::PostStepDoIt(
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const G4Track& trackData,
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const G4Step& stepData)
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{
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const G4DynamicParticle* aParticle ;
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G4Material* aMaterial;
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G4double KineticEnergy,TotalEnergy,TotalMomentum,
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betasquare,MaxKineticEnergyTransfer,
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DeltaKineticEnergy,DeltaTotalMomentum,costheta,sintheta,phi,
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dirx,diry,dirz,finalKineticEnergy,finalPx,finalPy,finalPz,
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x,xc,grej,Psquare,Esquare,summass,rate,grejc,finalMomentum ;
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aParticleChange.Initialize(trackData) ;
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aMaterial = trackData.GetMaterial() ;
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aParticle = trackData.GetDynamicParticle() ;
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KineticEnergy=aParticle->GetKineticEnergy();
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TotalEnergy=KineticEnergy + ParticleMass ;
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Psquare=KineticEnergy*(TotalEnergy+ParticleMass) ;
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Esquare=TotalEnergy*TotalEnergy ;
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summass = ParticleMass + electron_mass_c2 ;
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G4ParticleMomentum ParticleDirection = aParticle->GetMomentumDirection() ;
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DeltaCutInKineticEnergyNow = DeltaCutInKineticEnergy[aMaterial->GetIndex()];
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// some kinematics......................
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betasquare=Psquare/Esquare ;
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MaxKineticEnergyTransfer = 2.*electron_mass_c2*Psquare
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/(summass*summass+2.*electron_mass_c2*KineticEnergy);
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// sampling kinetic energy of the delta ray
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if( MaxKineticEnergyTransfer <= DeltaCutInKineticEnergyNow )
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{
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// there is no change at all).....
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return G4VContinuousDiscreteProcess::PostStepDoIt(trackData,stepData);
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}
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else
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{
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// normal case ......................................
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xc=DeltaCutInKineticEnergyNow/MaxKineticEnergyTransfer ;
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rate=MaxKineticEnergyTransfer/TotalEnergy ;
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// sampling follows ...
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grejc=1.-betasquare*xc ;
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do {
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x=xc/(1.-(1.-xc)*G4UniformRand());
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grej=(1.-x*betasquare)/grejc ;
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} while( G4UniformRand()>grej );
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}
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DeltaKineticEnergy = x * MaxKineticEnergyTransfer ;
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if(DeltaKineticEnergy <= 0.)
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return G4VContinuousDiscreteProcess::PostStepDoIt(trackData,stepData);
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DeltaTotalMomentum = sqrt(DeltaKineticEnergy * (DeltaKineticEnergy +
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2. * electron_mass_c2 )) ;
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TotalMomentum = sqrt(Psquare) ;
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costheta = DeltaKineticEnergy * (TotalEnergy + electron_mass_c2)
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/(DeltaTotalMomentum * TotalMomentum) ;
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// protection against costheta > 1 or < -1 ---------------
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if ( costheta < -1. )
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costheta = -1. ;
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if ( costheta > +1. )
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costheta = +1. ;
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// direction of the delta electron ........
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phi = twopi * G4UniformRand() ;
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sintheta = sqrt((1.+costheta)*(1.-costheta));
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dirx = sintheta * cos(phi) ;
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diry = sintheta * sin(phi) ;
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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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finalKineticEnergy = KineticEnergy - DeltaKineticEnergy ;
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if (finalKineticEnergy > 0.)
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{
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// changed energy and momentum of the actual particle
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finalMomentum=sqrt(finalKineticEnergy*
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(finalKineticEnergy+2.*ParticleMass)) ;
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finalPx = (TotalMomentum*ParticleDirection.x()
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-DeltaTotalMomentum*DeltaDirection.x())/finalMomentum ;
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finalPy = (TotalMomentum*ParticleDirection.y()
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-DeltaTotalMomentum*DeltaDirection.y())/finalMomentum ;
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finalPz = (TotalMomentum*ParticleDirection.z()
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-DeltaTotalMomentum*DeltaDirection.z())/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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aParticleChange.SetStatusChange(fStopAndKill);
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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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return G4VContinuousDiscreteProcess::PostStepDoIt(trackData,stepData);
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}
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void G4ionIonisation::PrintInfoDefinition()
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{
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G4String comments = " Knock-on electron cross sections . ";
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comments += "\n MeanFreePath is computed at tracking time.\n";
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comments += " delta ray energy sampled from differential Xsection.";
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G4cout << endl << GetProcessName() << ": " << comments << endl;
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}
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