Import Geant4 9.2.0 source tree
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Gabriele Cosmo
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//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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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. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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// $Id: G4eBremsstrahlungRelModel.cc,v 1.12 2008/11/13 23:28:27 schaelic Exp $
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// GEANT4 tag $Name: geant4-09-02 $
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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: G4eBremsstrahlungRelModel
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//
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// Author: Andreas Schaelicke
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//
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// Creation date: 12.08.2008
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//
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// Modifications:
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//
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// 13.11.08 add SetLPMflag and SetLPMconstant methods
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// 13.11.08 change default LPMconstant value
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//
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// Main References:
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// Y.-S.Tsai, Rev. Mod. Phys. 46 (1974) 815; Rev. Mod. Phys. 49 (1977) 421.
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// S.Klein, Rev. Mod. Phys. 71 (1999) 1501.
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// T.Stanev et.al., Phys. Rev. D25 (1982) 1291.
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// M.L.Ter-Mikaelian, High-energy Electromagnetic Processes in Condensed Media, Wiley, 1972.
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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 "G4eBremsstrahlungRelModel.hh"
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#include "G4Electron.hh"
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#include "G4Positron.hh"
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#include "G4Gamma.hh"
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#include "Randomize.hh"
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#include "G4Material.hh"
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#include "G4Element.hh"
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#include "G4ElementVector.hh"
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#include "G4ProductionCutsTable.hh"
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#include "G4ParticleChangeForLoss.hh"
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#include "G4LossTableManager.hh"
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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const G4double G4eBremsstrahlungRelModel::xgi[]={ 0.0199, 0.1017, 0.2372, 0.4083,
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0.5917, 0.7628, 0.8983, 0.9801 };
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const G4double G4eBremsstrahlungRelModel::wgi[]={ 0.0506, 0.1112, 0.1569, 0.1813,
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0.1813, 0.1569, 0.1112, 0.0506 };
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const G4double G4eBremsstrahlungRelModel::Fel_light[] = {0., 5.31 , 4.79 , 4.74 , 4.71} ;
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const G4double G4eBremsstrahlungRelModel::Finel_light[] = {0., 6.144 , 5.621 , 5.805 , 5.924} ;
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using namespace std;
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G4eBremsstrahlungRelModel::G4eBremsstrahlungRelModel(const G4ParticleDefinition* p,
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const G4String& name)
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: G4VEmModel(name),
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particle(0),
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fXiLPM(0), fPhiLPM(0), fGLPM(0),
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isElectron(true),
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fMigdalConstant(classic_electr_radius*electron_Compton_length*electron_Compton_length*4.0*pi),
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fLPMconstant(fine_structure_const*electron_mass_c2*electron_mass_c2/(4.*pi*hbarc)*0.5),
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bremFactor(fine_structure_const*classic_electr_radius*classic_electr_radius*16./3.),
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use_completescreening(true),isInitialised(false)
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{
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if(p) SetParticle(p);
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theGamma = G4Gamma::Gamma();
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minThreshold = 1.0*keV;
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SetLowEnergyLimit(GeV);
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nist = G4NistManager::Instance();
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InitialiseConstants();
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SetLPMFlag(true);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eBremsstrahlungRelModel::InitialiseConstants()
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{
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facFel = log(184.15);
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facFinel = log(1194.);
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preS1 = 1./(184.15*184.15);
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logTwo = log(2.);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4eBremsstrahlungRelModel::~G4eBremsstrahlungRelModel()
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{
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eBremsstrahlungRelModel::SetParticle(const G4ParticleDefinition* p)
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{
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particle = p;
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particleMass = p->GetPDGMass();
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if(p == G4Electron::Electron()) isElectron = true;
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else isElectron = false;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4eBremsstrahlungRelModel::MinEnergyCut(const G4ParticleDefinition*,
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const G4MaterialCutsCouple*)
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{
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return minThreshold;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eBremsstrahlungRelModel::SetupForMaterial(const G4ParticleDefinition*,
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const G4Material* mat, G4double kineticEnergy)
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{
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densityFactor = mat->GetElectronDensity()*fMigdalConstant;
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lpmEnergy = mat->GetRadlen()*fLPMconstant;
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// Threshold for LPM effect (i.e. below which LPM hidden by density effect)
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if (LPMFlag())
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energyThresholdLPM=sqrt(densityFactor)*lpmEnergy;
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else
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energyThresholdLPM=1.e39; // i.e. do not use LPM effect
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// calculate threshold for density effect
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kinEnergy = kineticEnergy;
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totalEnergy = kineticEnergy + particleMass;
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densityCorr = densityFactor*totalEnergy*totalEnergy;
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// define critical gamma energies (important for integration/dicing)
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klpm=totalEnergy*totalEnergy/lpmEnergy;
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kp=sqrt(densityCorr);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eBremsstrahlungRelModel::Initialise(const G4ParticleDefinition* p,
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const G4DataVector& cuts)
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{
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if(p) SetParticle(p);
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highKinEnergy = HighEnergyLimit();
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lowKinEnergy = LowEnergyLimit();
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currentZ = 0.;
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InitialiseElementSelectors(p, cuts);
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if(isInitialised) return;
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if(pParticleChange) {
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fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*>(pParticleChange);
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} else {
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fParticleChange = new G4ParticleChangeForLoss();
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}
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isInitialised = true;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4eBremsstrahlungRelModel::ComputeDEDXPerVolume(
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const G4Material* material,
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const G4ParticleDefinition* p,
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G4double kineticEnergy,
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G4double cutEnergy)
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{
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if(!particle) SetParticle(p);
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if(kineticEnergy < lowKinEnergy) return 0.0;
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G4double cut = std::min(cutEnergy, kineticEnergy);
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if(cut == 0.0) return 0.0;
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SetupForMaterial(particle, material,kineticEnergy);
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const G4ElementVector* theElementVector = material->GetElementVector();
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const G4double* theAtomicNumDensityVector = material->GetAtomicNumDensityVector();
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G4double dedx = 0.0;
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// loop for elements in the material
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for (size_t i=0; i<material->GetNumberOfElements(); i++) {
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G4VEmModel::SetCurrentElement((*theElementVector)[i]);
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SetCurrentElement((*theElementVector)[i]->GetZ());
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dedx += theAtomicNumDensityVector[i]*currentZ*currentZ*ComputeBremLoss(cut);
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}
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dedx *= bremFactor;
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return dedx;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4eBremsstrahlungRelModel::ComputeBremLoss(G4double cut)
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{
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G4double loss = 0.0;
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// number of intervals and integration step
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G4double vcut = cut/totalEnergy;
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G4int n = (G4int)(20*vcut) + 3;
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G4double delta = vcut/G4double(n);
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G4double e0 = 0.0;
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G4double xs;
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// integration
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for(G4int l=0; l<n; l++) {
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for(G4int i=0; i<8; i++) {
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G4double eg = (e0 + xgi[i]*delta)*totalEnergy;
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if(totalEnergy > energyThresholdLPM) {
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xs = ComputeRelDXSectionPerAtom(eg);
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} else {
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xs = ComputeDXSectionPerAtom(eg);
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}
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loss += wgi[i]*xs/(1.0 + densityCorr/(eg*eg));
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}
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e0 += delta;
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}
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loss *= delta*totalEnergy;
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return loss;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4eBremsstrahlungRelModel::ComputeCrossSectionPerAtom(
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const G4ParticleDefinition* p,
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G4double kineticEnergy,
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G4double Z, G4double,
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G4double cutEnergy,
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G4double maxEnergy)
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{
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if(!particle) SetParticle(p);
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if(kineticEnergy < lowKinEnergy) return 0.0;
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G4double cut = std::min(cutEnergy, kineticEnergy);
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G4double tmax = std::min(maxEnergy, kineticEnergy);
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if(cut >= tmax) return 0.0;
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SetCurrentElement(Z);
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G4double cross = ComputeXSectionPerAtom(cut);
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// allow partial integration
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if(tmax < kinEnergy) cross -= ComputeXSectionPerAtom(tmax);
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cross *= Z*Z*bremFactor;
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return cross;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4eBremsstrahlungRelModel::ComputeXSectionPerAtom(G4double cut)
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{
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G4double cross = 0.0;
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// number of intervals and integration step
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G4double vcut = log(cut/totalEnergy);
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G4double vmax = log(kinEnergy/totalEnergy);
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G4int n = (G4int)(0.45*(vmax - vcut)) + 4;
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// n=1; // integration test
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G4double delta = (vmax - vcut)/G4double(n);
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G4double e0 = vcut;
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G4double xs;
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// integration
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for(G4int l=0; l<n; l++) {
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for(G4int i=0; i<8; i++) {
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G4double eg = exp(e0 + xgi[i]*delta)*totalEnergy;
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if(totalEnergy > energyThresholdLPM) {
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xs = ComputeRelDXSectionPerAtom(eg);
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} else {
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xs = ComputeDXSectionPerAtom(eg);
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}
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cross += wgi[i]*xs/(1.0 + densityCorr/(eg*eg));
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}
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e0 += delta;
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}
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cross *= delta;
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return cross;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4eBremsstrahlungRelModel::CalcLPMFunctions(G4double k)
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{
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// *** calculate lpm variable s & sprime ***
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// Klein eqs. (78) & (79)
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G4double sprime = sqrt(0.125*k*lpmEnergy/(totalEnergy*(totalEnergy-k)));
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G4double s1 = preS1*z23;
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G4double logS1 = 2./3.*lnZ-2.*facFel;
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G4double logTS1 = logTwo+logS1;
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xiLPM = 2.;
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if (sprime>1)
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xiLPM = 1.;
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else if (sprime>sqrt(2.)*s1) {
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G4double h = log(sprime)/logTS1;
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xiLPM = 1+h-0.08*(1-h)*(1-sqr(1-h))/logTS1;
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}
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G4double s = sprime/sqrt(xiLPM);
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// *** merging with density effect*** should be only necessary in region "close to" kp, e.g. k<100*kp
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// using Ter-Mikaelian eq. (20.9)
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G4double k2 = k*k;
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s = s * (1 + (densityCorr/k2) );
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// recalculate Xi using modified s above
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// Klein eq. (75)
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xiLPM = 1.;
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if (s<=s1) xiLPM = 2.;
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else if ( (s1<s) && (s<=1) ) xiLPM = 1. + log(s)/logS1;
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// *** calculate supression functions phi and G ***
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// Klein eqs. (77)
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G4double s2=s*s;
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G4double s3=s*s2;
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G4double s4=s2*s2;
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if (s<0.1) {
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// high suppression limit
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phiLPM = 6.*s - 18.84955592153876*s2 + 39.47841760435743*s3
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- 57.69873135166053*s4;
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gLPM = 37.69911184307752*s2 - 236.8705056261446*s3 + 807.7822389*s4;
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}
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else if (s<1.9516) {
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// intermediate suppression
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// using eq.77 approxim. valid s<2.
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phiLPM = 1.-exp(-6.*s*(1.+(3.-pi)*s)
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+s3/(0.623+0.795*s+0.658*s2));
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if (s<0.415827397755) {
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// using eq.77 approxim. valid 0.07<s<2
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G4double psiLPM = 1-exp(-4*s-8*s2/(1+3.936*s+4.97*s2-0.05*s3+7.50*s4));
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gLPM = 3*psiLPM-2*phiLPM;
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}
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else {
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// using alternative parametrisiation
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G4double pre = -0.16072300849123999 + s*3.7550300067531581 + s2*-1.7981383069010097
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+ s3*0.67282686077812381 + s4*-0.1207722909879257;
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gLPM = tanh(pre);
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}
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}
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else {
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// low suppression limit valid s>2.
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phiLPM = 1. - 0.0119048/s4;
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gLPM = 1. - 0.0230655/s4;
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}
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// *** make sure suppression is smaller than 1 ***
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// *** caused by Migdal approximation in xi ***
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if (xiLPM*phiLPM>1. || s>0.57) xiLPM=1./phiLPM;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4eBremsstrahlungRelModel::ComputeRelDXSectionPerAtom(G4double gammaEnergy)
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// Ultra relativistic model
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// only valid for very high energies, but includes LPM suppression
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// * complete screening
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{
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if(gammaEnergy < 0.0) return 0.0;
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G4double y = gammaEnergy/totalEnergy;
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G4double y2 = y*y*.25;
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G4double yone2 = (1.-y+2.*y2);
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// ** form factors complete screening case **
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// ** calc LPM functions -- include ter-mikaelian merging with density effect **
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// G4double xiLPM, gLPM, phiLPM; // to be made member variables !!!
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CalcLPMFunctions(gammaEnergy);
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G4double mainLPM = xiLPM*(y2 * gLPM + yone2*phiLPM) * ( (Fel-fCoulomb) + Finel/currentZ );
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G4double secondTerm = (1.-y)/12.*(1.+1./currentZ);
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G4double cross = mainLPM+secondTerm;
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return cross;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
|
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G4double G4eBremsstrahlungRelModel::ComputeDXSectionPerAtom(G4double gammaEnergy)
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||||
// Relativistic model
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// only valid for high energies (and if LPM suppression does not play a role)
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||||
// * screening according to thomas-fermi-Model (only valid for Z>5)
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||||
// * no LPM effect
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||||
{
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||||
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if(gammaEnergy < 0.0) return 0.0;
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||||
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||||
G4double y = gammaEnergy/totalEnergy;
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||||
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G4double main=0.,secondTerm=0.;
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||||
if (use_completescreening|| currentZ<5) {
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// ** form factors complete screening case **
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||||
main = (3./4.*y*y - y + 1.) * ( (Fel-fCoulomb) + Finel/currentZ );
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||||
secondTerm = (1.-y)/12.*(1.+1./currentZ);
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||||
}
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||||
else {
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||||
// ** intermediate screening using Thomas-Fermi FF from Tsai only valid for Z>=5**
|
||||
G4double dd=100.*electron_mass_c2*y/(totalEnergy-gammaEnergy);
|
||||
G4double gg=dd*z13;
|
||||
G4double eps=dd*z23;
|
||||
G4double phi1=Phi1(gg,currentZ), phi1m2=Phi1M2(gg,currentZ);
|
||||
G4double psi1=Psi1(eps,currentZ), psi1m2=Psi1M2(eps,currentZ);
|
||||
|
||||
main = (3./4.*y*y - y + 1.) * ( (0.25*phi1-1./3.*lnZ-fCoulomb) + (0.25*psi1-2./3.*lnZ)/currentZ );
|
||||
secondTerm = (1.-y)/8.*(phi1m2+psi1m2/currentZ);
|
||||
}
|
||||
G4double cross = main+secondTerm;
|
||||
return cross;
|
||||
}
|
||||
|
||||
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
|
||||
|
||||
void G4eBremsstrahlungRelModel::SampleSecondaries(
|
||||
std::vector<G4DynamicParticle*>* vdp,
|
||||
const G4MaterialCutsCouple* couple,
|
||||
const G4DynamicParticle* dp,
|
||||
G4double cutEnergy,
|
||||
G4double maxEnergy)
|
||||
{
|
||||
G4double kineticEnergy = dp->GetKineticEnergy();
|
||||
if(kineticEnergy < lowKinEnergy) return;
|
||||
G4double cut = std::min(cutEnergy, kineticEnergy);
|
||||
G4double emax = std::min(maxEnergy, kineticEnergy);
|
||||
if(cut >= emax) return;
|
||||
|
||||
SetupForMaterial(particle, couple->GetMaterial(),kineticEnergy);
|
||||
|
||||
const G4Element* elm =
|
||||
SelectRandomAtom(couple,particle,kineticEnergy,cut,emax);
|
||||
SetCurrentElement(elm->GetZ());
|
||||
|
||||
kinEnergy = kineticEnergy;
|
||||
totalEnergy = kineticEnergy + particleMass;
|
||||
densityCorr = densityFactor*totalEnergy*totalEnergy;
|
||||
G4ThreeVector direction = dp->GetMomentumDirection();
|
||||
|
||||
// G4double fmax= fMax;
|
||||
G4bool highe = true;
|
||||
if(totalEnergy < energyThresholdLPM) highe = false;
|
||||
|
||||
G4double xmin = log(cut*cut + densityCorr);
|
||||
G4double xmax = log(emax*emax + densityCorr);
|
||||
G4double gammaEnergy, f, x;
|
||||
|
||||
do {
|
||||
x = exp(xmin + G4UniformRand()*(xmax - xmin)) - densityCorr;
|
||||
if(x < 0.0) x = 0.0;
|
||||
gammaEnergy = sqrt(x);
|
||||
if(highe) f = ComputeRelDXSectionPerAtom(gammaEnergy);
|
||||
else f = ComputeDXSectionPerAtom(gammaEnergy);
|
||||
|
||||
if ( f > fMax ) {
|
||||
G4cout << "### G4eBremsstrahlungRelModel Warning: Majoranta exceeded! "
|
||||
<< f << " > " << fMax
|
||||
<< " Egamma(MeV)= " << gammaEnergy
|
||||
<< " E(mEV)= " << kineticEnergy
|
||||
<< G4endl;
|
||||
}
|
||||
|
||||
} while (f < fMax*G4UniformRand());
|
||||
|
||||
//
|
||||
// angles of the emitted gamma. ( Z - axis along the parent particle)
|
||||
//
|
||||
// universal distribution suggested by L. Urban
|
||||
// (Geant3 manual (1993) Phys211),
|
||||
// derived from Tsai distribution (Rev Mod Phys 49,421(1977))
|
||||
|
||||
G4double u;
|
||||
const G4double a1 = 0.625 , a2 = 3.*a1 , d = 27. ;
|
||||
|
||||
if (9./(9.+d) > G4UniformRand()) u = - log(G4UniformRand()*G4UniformRand())/a1;
|
||||
else u = - log(G4UniformRand()*G4UniformRand())/a2;
|
||||
|
||||
G4double theta = u*particleMass/totalEnergy;
|
||||
G4double sint = sin(theta);
|
||||
G4double phi = twopi * G4UniformRand();
|
||||
G4ThreeVector gammaDirection(sint*cos(phi),sint*sin(phi), cos(theta));
|
||||
gammaDirection.rotateUz(direction);
|
||||
|
||||
// create G4DynamicParticle object for the Gamma
|
||||
G4DynamicParticle* g = new G4DynamicParticle(theGamma,gammaDirection,
|
||||
gammaEnergy);
|
||||
vdp->push_back(g);
|
||||
|
||||
G4double totMomentum = sqrt(kineticEnergy*(totalEnergy + electron_mass_c2));
|
||||
G4ThreeVector dir = totMomentum*direction - gammaEnergy*gammaDirection;
|
||||
direction = dir.unit();
|
||||
|
||||
// energy of primary
|
||||
G4double finalE = kineticEnergy - gammaEnergy;
|
||||
|
||||
// stop tracking and create new secondary instead of primary
|
||||
if(gammaEnergy > SecondaryThreshold()) {
|
||||
fParticleChange->ProposeTrackStatus(fStopAndKill);
|
||||
fParticleChange->SetProposedKineticEnergy(0.0);
|
||||
G4DynamicParticle* el =
|
||||
new G4DynamicParticle(const_cast<G4ParticleDefinition*>(particle),
|
||||
direction, finalE);
|
||||
vdp->push_back(el);
|
||||
|
||||
// continue tracking
|
||||
} else {
|
||||
fParticleChange->SetProposedMomentumDirection(direction);
|
||||
fParticleChange->SetProposedKineticEnergy(finalE);
|
||||
}
|
||||
}
|
||||
|
||||
//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
|
||||
|
||||
|
||||
Reference in New Issue
Block a user