Import Geant4 5.0.0 source tree
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Gabriele Cosmo
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//
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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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// -------------------------------------------------------------------
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//
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// GEANT4 Class file
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//
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//
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// File name: G4UniversalFluctuation
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//
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// Author: Vladimir Ivanchenko
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//
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// Creation date: 03.01.2002
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//
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// Modifications:
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//
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// Class Description:
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//
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// -------------------------------------------------------------------
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//
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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#include "G4UniversalFluctuation.hh"
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#include "Randomize.hh"
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#include "G4Poisson.hh"
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#include "G4Step.hh"
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#include "G4Material.hh"
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#include "G4DynamicParticle.hh"
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#include "G4ParticleDefinition.hh"
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4UniversalFluctuation::G4UniversalFluctuation()
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:G4VEmFluctuationModel(),
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minNumberInteractionsBohr(10.0),
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theBohrBeta2(50.0*keV/proton_mass_c2),
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minLoss(0.000001*eV),
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problim(0.01),
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alim(10.),
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nmaxCont1(4),
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nmaxCont2(16)
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{
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lastMaterial = 0;
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sumalim = -log(problim);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4UniversalFluctuation::~G4UniversalFluctuation()
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{}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4UniversalFluctuation::Initialise(const G4ParticleDefinition* part)
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{
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particle = part;
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particleMass = part->GetPDGMass();
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G4double q = part->GetPDGCharge()/eplus;
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chargeSquare = q*q;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4UniversalFluctuation::SampleFluctuations(const G4Material* material,
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const G4DynamicParticle* dp,
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G4double& tmax,
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G4double& length,
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G4double meanLoss)
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{
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// calculate actual loss from the mean loss
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// The model used to get the fluctuation is essentially the same
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// as in Glandz in Geant3.
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// shortcut for very very small loss
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if(meanLoss < minLoss) return;
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G4double preStepKinEnergy = dp->GetKineticEnergy();
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if(dp->GetDefinition() != particle) {
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particleMass = dp->GetMass();
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G4double q = dp->GetCharge();
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chargeSquare = q*q;
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}
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// data members for a given material
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if(material != lastMaterial) {
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ipotFluct = material->GetIonisation()->GetMeanExcitationEnergy();
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electronDensity = material->GetElectronDensity();
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// zeff = electronDensity/(material->GetTotNbOfAtomsPerVolume());
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}
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// get particle data
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G4double tau = preStepKinEnergy/particleMass;
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G4double tau1 = tau + 1.0;
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G4double tau2 = tau * (tau+2.0);
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G4double beta2 = tau2/(tau1*tau1);
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// Validity range for delta electron cross section
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G4double loss, siga;
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// Gaussian fluctuation
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if(meanLoss >= minNumberInteractionsBohr*tmax || tmax <= ipotFluct*minNumberInteractionsBohr)
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{
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siga = tmax * (1.0-0.5*beta2) * length * twopi_mc2_rcl2
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* electronDensity / beta2;
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siga = sqrt(siga * chargeSquare);
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/*
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// High velocity or negatively charged particle
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if( beta2 > 3.0*theBohrBeta2*zeff || charge < 0.0) {
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siga = sqrt( siga * chargeSquare ) ;
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// Low velocity - additional ion charge fluctuations according to
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// Q.Yang et al., NIM B61(1991)149-155.
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} else {
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G4double chu = theIonChuFluctuationModel->TheValue(particle, material);
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G4double yang = theIonYangFluctuationModel->TheValue(particle, material);
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siga = sqrt( siga * (chargeSquare * chu + yang)) ;
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}
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*/
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do {
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loss = G4RandGauss::shoot(meanLoss,siga);
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} while (loss < 0.);
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meanLoss = loss;
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if(lastMaterial != material) lastMaterial = material;
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return;
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}
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// Non Gaussian fluctuation
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if(material != lastMaterial) {
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zeff = electronDensity/(material->GetTotNbOfAtomsPerVolume());
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f1Fluct = material->GetIonisation()->GetF1fluct();
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f2Fluct = material->GetIonisation()->GetF2fluct();
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e1Fluct = material->GetIonisation()->GetEnergy1fluct();
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e2Fluct = material->GetIonisation()->GetEnergy2fluct();
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e1LogFluct = material->GetIonisation()->GetLogEnergy1fluct();
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e2LogFluct = material->GetIonisation()->GetLogEnergy2fluct();
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rateFluct = material->GetIonisation()->GetRateionexcfluct();
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ipotLogFluct= material->GetIonisation()->GetLogMeanExcEnergy();
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lastMaterial = material;
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}
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G4double suma,w1,w2,C,e0,lossc,w;
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G4double a1,a2,a3;
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G4int p1,p2,p3;
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G4int nb;
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G4double corrfac, na,alfa,rfac,namean,sa,alfa1,ea,sea;
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G4double dp3;
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w1 = tmax/ipotFluct;
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w2 = log(2.*electron_mass_c2*tau2);
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C = meanLoss*(1.-rateFluct)/(w2-ipotLogFluct-beta2);
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a1 = C*f1Fluct*(w2-e1LogFluct-beta2)/e1Fluct;
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a2 = C*f2Fluct*(w2-e2LogFluct-beta2)/e2Fluct;
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a3 = rateFluct*meanLoss*(tmax-ipotFluct)/(ipotFluct*tmax*log(w1));
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if(a1 < 0.) a1 = 0.;
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if(a2 < 0.) a2 = 0.;
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if(a3 < 0.) a3 = 0.;
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suma = a1+a2+a3;
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loss = 0. ;
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if(suma < sumalim) // very small Step
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{
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e0 = material->GetIonisation()->GetEnergy0fluct();
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if(tmax == ipotFluct)
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{
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a3 = meanLoss/e0;
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if(a3>alim)
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{
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siga=sqrt(a3) ;
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p3 = G4std::max(0,int(G4RandGauss::shoot(a3,siga)+0.5));
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}
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else
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p3 = G4Poisson(a3);
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loss = p3*e0 ;
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if(p3 > 0)
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loss += (1.-2.*G4UniformRand())*e0 ;
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}
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else
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{
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tmax = tmax-ipotFluct+e0 ;
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a3 = meanLoss*(tmax-e0)/(tmax*e0*log(tmax/e0));
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if(a3>alim)
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{
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siga=sqrt(a3) ;
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p3 = G4std::max(0,int(G4RandGauss::shoot(a3,siga)+0.5));
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}
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else
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p3 = G4Poisson(a3);
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if(p3 > 0)
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{
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w = (tmax-e0)/tmax ;
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if(p3 > nmaxCont2)
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{
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dp3 = G4float(p3) ;
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corrfac = dp3/G4float(nmaxCont2) ;
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p3 = nmaxCont2 ;
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}
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else
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corrfac = 1. ;
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for(G4int i=0; i<p3; i++) loss += 1./(1.-w*G4UniformRand()) ;
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loss *= e0*corrfac ;
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}
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}
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}
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else // not so small Step
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{
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// excitation type 1
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if(a1>alim)
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{
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siga=sqrt(a1) ;
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p1 = G4std::max(0,int(G4RandGauss::shoot(a1,siga)+0.5));
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}
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else
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p1 = G4Poisson(a1);
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// excitation type 2
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if(a2>alim)
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{
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siga=sqrt(a2) ;
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p2 = G4std::max(0,int(G4RandGauss::shoot(a2,siga)+0.5));
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}
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else
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p2 = G4Poisson(a2);
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loss = p1*e1Fluct+p2*e2Fluct;
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// smearing to avoid unphysical peaks
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if(p2 > 0)
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loss += (1.-2.*G4UniformRand())*e2Fluct;
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else if (loss>0.)
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loss += (1.-2.*G4UniformRand())*e1Fluct;
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// ionisation .......................................
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if(a3 > 0.)
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{
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if(a3>alim)
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{
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siga=sqrt(a3) ;
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p3 = G4std::max(0,int(G4RandGauss::shoot(a3,siga)+0.5));
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}
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else
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p3 = G4Poisson(a3);
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lossc = 0.;
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if(p3 > 0)
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{
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na = 0.;
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alfa = 1.;
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if (p3 > nmaxCont2)
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{
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dp3 = G4float(p3);
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rfac = dp3/(G4float(nmaxCont2)+dp3);
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namean = G4float(p3)*rfac;
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sa = G4float(nmaxCont1)*rfac;
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na = G4RandGauss::shoot(namean,sa);
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if (na > 0.)
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{
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alfa = w1*G4float(nmaxCont2+p3)/
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(w1*G4float(nmaxCont2)+G4float(p3));
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alfa1 = alfa*log(alfa)/(alfa-1.);
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ea = na*ipotFluct*alfa1;
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sea = ipotFluct*sqrt(na*(alfa-alfa1*alfa1));
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lossc += G4RandGauss::shoot(ea,sea);
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}
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}
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nb = G4int(G4float(p3)-na);
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if (nb > 0)
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{
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w2 = alfa*ipotFluct;
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w = (tmax-w2)/tmax;
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for (G4int k=0; k<nb; k++) lossc += w2/(1.-w*G4UniformRand());
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}
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}
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loss += lossc;
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}
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}
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meanLoss = loss;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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