Gabriele Cosmo
381 lines
14 KiB
C++
381 lines
14 KiB
C++
//
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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: G4LivermoreGammaConversionModelRC.cc,v 1.1 2010-11-10 17:12:22 flongo Exp $
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// GEANT4 tag $Name: not supported by cvs2svn $
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//
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// Author: Francesco Longo & Gerardo Depaola
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// on base of G4LivermoreGammaConversionModel
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//
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// History:
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// --------
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// 12 Apr 2009 V Ivanchenko Cleanup initialisation and generation of secondaries:
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// - apply internal high-energy limit only in constructor
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// - do not apply low-energy limit (default is 0)
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// - use CLHEP electron mass for low-enegry limit
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// - remove MeanFreePath method and table
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#include "G4LivermoreGammaConversionModelRC.hh"
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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using namespace std;
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4LivermoreGammaConversionModelRC::G4LivermoreGammaConversionModelRC(const G4ParticleDefinition*,
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const G4String& nam)
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:G4VEmModel(nam),smallEnergy(2.*MeV),isInitialised(false),
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crossSectionHandler(0),meanFreePathTable(0)
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{
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lowEnergyLimit = 2.0*electron_mass_c2;
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highEnergyLimit = 100 * GeV;
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SetHighEnergyLimit(highEnergyLimit);
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verboseLevel= 0;
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// Verbosity scale:
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// 0 = nothing
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// 1 = warning for energy non-conservation
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// 2 = details of energy budget
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// 3 = calculation of cross sections, file openings, sampling of atoms
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// 4 = entering in methods
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if(verboseLevel > 0) {
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G4cout << "Livermore Gamma conversion is constructed " << G4endl
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<< "Energy range: "
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<< lowEnergyLimit / MeV << " MeV - "
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<< highEnergyLimit / GeV << " GeV"
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<< G4endl;
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}
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4LivermoreGammaConversionModelRC::~G4LivermoreGammaConversionModelRC()
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{
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if (crossSectionHandler) delete crossSectionHandler;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void
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G4LivermoreGammaConversionModelRC::Initialise(const G4ParticleDefinition*,
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const G4DataVector&)
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{
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if (verboseLevel > 3)
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G4cout << "Calling G4LivermoreGammaConversionModelRC::Initialise()" << G4endl;
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if (crossSectionHandler)
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{
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crossSectionHandler->Clear();
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delete crossSectionHandler;
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}
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// Read data tables for all materials
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crossSectionHandler = new G4CrossSectionHandler();
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crossSectionHandler->Initialise(0,lowEnergyLimit,100.*GeV,400);
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G4String crossSectionFile = "pair/pp-cs-";
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crossSectionHandler->LoadData(crossSectionFile);
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//
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if (verboseLevel > 2)
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G4cout << "Loaded cross section files for Livermore Gamma Conversion model RC" << G4endl;
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if (verboseLevel > 0) {
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G4cout << "Livermore Gamma Conversion model is initialized " << G4endl
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<< "Energy range: "
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<< LowEnergyLimit() / MeV << " MeV - "
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<< HighEnergyLimit() / GeV << " GeV"
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<< G4endl;
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}
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if(isInitialised) return;
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fParticleChange = GetParticleChangeForGamma();
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isInitialised = true;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double
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G4LivermoreGammaConversionModelRC::ComputeCrossSectionPerAtom(const G4ParticleDefinition*,
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G4double GammaEnergy,
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G4double Z, G4double,
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G4double, G4double)
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{
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if (verboseLevel > 3) {
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G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreGammaConversionModelRC"
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<< G4endl;
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}
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if (GammaEnergy < lowEnergyLimit || GammaEnergy > highEnergyLimit) return 0;
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G4double cs = crossSectionHandler->FindValue(G4int(Z), GammaEnergy);
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return cs;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4LivermoreGammaConversionModelRC::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
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const G4MaterialCutsCouple* couple,
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const G4DynamicParticle* aDynamicGamma,
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G4double,
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G4double)
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{
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// The energies of the e+ e- secondaries are sampled using the Bethe - Heitler
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// cross sections with Coulomb correction. A modified version of the random
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// number techniques of Butcher & Messel is used (Nuc Phys 20(1960),15).
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// Note 1 : Effects due to the breakdown of the Born approximation at low
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// energy are ignored.
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// Note 2 : The differential cross section implicitly takes account of
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// pair creation in both nuclear and atomic electron fields. However triplet
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// prodution is not generated.
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if (verboseLevel > 3)
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G4cout << "Calling SampleSecondaries() of G4LivermoreGammaConversionModelRC" << G4endl;
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G4double photonEnergy = aDynamicGamma->GetKineticEnergy();
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G4ParticleMomentum photonDirection = aDynamicGamma->GetMomentumDirection();
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G4double epsilon ;
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G4double epsilon0 = electron_mass_c2 / photonEnergy ;
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G4double electronTotEnergy;
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G4double positronTotEnergy;
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// Do it fast if photon energy < 2. MeV
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if (photonEnergy < smallEnergy )
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{
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epsilon = epsilon0 + (0.5 - epsilon0) * G4UniformRand();
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if (G4int(2*G4UniformRand()))
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{
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electronTotEnergy = (1. - epsilon) * photonEnergy;
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positronTotEnergy = epsilon * photonEnergy;
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}
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else
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{
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positronTotEnergy = (1. - epsilon) * photonEnergy;
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electronTotEnergy = epsilon * photonEnergy;
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}
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}
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else
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{
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// Select randomly one element in the current material
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//const G4Element* element = crossSectionHandler->SelectRandomElement(couple,photonEnergy);
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const G4ParticleDefinition* particle = aDynamicGamma->GetDefinition();
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const G4Element* element = SelectRandomAtom(couple,particle,photonEnergy);
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G4cout << "G4LivermoreGammaConversionModelRC::SampleSecondaries" << G4endl;
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if (element == 0)
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{
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G4cout << "G4LivermoreGammaConversionModelRC::SampleSecondaries - element = 0"
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<< G4endl;
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return;
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}
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G4IonisParamElm* ionisation = element->GetIonisation();
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if (ionisation == 0)
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{
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G4cout << "G4LivermoreGammaConversionModelRC::SampleSecondaries - ionisation = 0"
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<< G4endl;
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return;
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}
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// Extract Coulomb factor for this Element
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G4double fZ = 8. * (ionisation->GetlogZ3());
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if (photonEnergy > 50. * MeV) fZ += 8. * (element->GetfCoulomb());
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// Limits of the screening variable
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G4double screenFactor = 136. * epsilon0 / (element->GetIonisation()->GetZ3()) ;
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G4double screenMax = std::exp ((42.24 - fZ)/8.368) - 0.952 ;
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G4double screenMin = std::min(4.*screenFactor,screenMax) ;
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// Limits of the energy sampling
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G4double epsilon1 = 0.5 - 0.5 * std::sqrt(1. - screenMin / screenMax) ;
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G4double epsilonMin = std::max(epsilon0,epsilon1);
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G4double epsilonRange = 0.5 - epsilonMin ;
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// Sample the energy rate of the created electron (or positron)
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G4double screen;
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G4double gReject ;
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G4double f10 = ScreenFunction1(screenMin) - fZ;
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G4double f20 = ScreenFunction2(screenMin) - fZ;
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G4double normF1 = std::max(f10 * epsilonRange * epsilonRange,0.);
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G4double normF2 = std::max(1.5 * f20,0.);
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G4double a=393.3750918, b=115.3070201, c=810.6428451, d=19.96497475, e=1016.874592, f=1.936685510,
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g=751.2140962, h=0.099751048, i=299.9466339, j=0.002057250, k=49.81034926;
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G4double aa=-18.6371131, bb=-1729.95248, cc=9450.971186, dd=106336.0145, ee=55143.09287, ff=-117602.840,
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gg=-721455.467, hh=693957.8635, ii=156266.1085, jj=533209.9347;
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G4double Rechazo = 0.;
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G4double logepsMin = log(epsilonMin);
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G4double NormaRC = a + b*logepsMin + c/logepsMin + d*pow(logepsMin,2.) + e/pow(logepsMin,2.) + f*pow(logepsMin,3.) +
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g/pow(logepsMin,3.) + h*pow(logepsMin,4.) + i/pow(logepsMin,4.) + j*pow(logepsMin,5.) +
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k/pow(logepsMin,5.);
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do {
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do {
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if (normF1 / (normF1 + normF2) > G4UniformRand() )
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{
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epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.3333) ;
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screen = screenFactor / (epsilon * (1. - epsilon));
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gReject = (ScreenFunction1(screen) - fZ) / f10 ;
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}
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else
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{
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epsilon = epsilonMin + epsilonRange * G4UniformRand();
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screen = screenFactor / (epsilon * (1 - epsilon));
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gReject = (ScreenFunction2(screen) - fZ) / f20 ;
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}
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} while ( gReject < G4UniformRand() );
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if (G4int(2*G4UniformRand())) epsilon = (1. - epsilon); // Extención de Epsilon hasta 1.
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G4double logepsilon = log(epsilon);
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G4double deltaP_R1 = 1. + (a + b*logepsilon + c/logepsilon + d*pow(logepsilon,2.) + e/pow(logepsilon,2.) +
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f*pow(logepsilon,3.) + g/pow(logepsilon,3.) + h*pow(logepsilon,4.) + i/pow(logepsilon,4.) +
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j*pow(logepsilon,5.) + k/pow(logepsilon,5.))/100.;
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G4double deltaP_R2 = 1.+((aa + cc*logepsilon + ee*pow(logepsilon,2.) + gg*pow(logepsilon,3.) + ii*pow(logepsilon,4.))
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/ (1. + bb*logepsilon + dd*pow(logepsilon,2.) + ff*pow(logepsilon,3.) + hh*pow(logepsilon,4.)
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+ jj*pow(logepsilon,5.) ))/100.;
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if (epsilon <= 0.5)
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{
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Rechazo = deltaP_R1/NormaRC;
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}
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else
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{
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Rechazo = deltaP_R2/NormaRC;
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}
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G4cout << Rechazo << " " << NormaRC << " " << epsilon << G4endl;
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} while (Rechazo < G4UniformRand() );
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electronTotEnergy = (1. - epsilon) * photonEnergy;
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positronTotEnergy = epsilon * photonEnergy;
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} // End of epsilon sampling
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// Fix charges randomly
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// Scattered electron (positron) angles. ( Z - axis along the parent photon)
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// Universal distribution suggested by L. Urban (Geant3 manual (1993) Phys211),
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// derived from Tsai distribution (Rev. Mod. Phys. 49, 421 (1977)
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G4double u;
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const G4double a1 = 0.625;
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G4double a2 = 3. * a1;
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// G4double d = 27. ;
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// if (9. / (9. + d) > G4UniformRand())
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if (0.25 > G4UniformRand())
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{
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u = - std::log(G4UniformRand() * G4UniformRand()) / a1 ;
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}
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else
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{
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u = - std::log(G4UniformRand() * G4UniformRand()) / a2 ;
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}
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G4double thetaEle = u*electron_mass_c2/electronTotEnergy;
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G4double thetaPos = u*electron_mass_c2/positronTotEnergy;
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G4double phi = twopi * G4UniformRand();
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G4double dxEle= std::sin(thetaEle)*std::cos(phi),dyEle= std::sin(thetaEle)*std::sin(phi),dzEle=std::cos(thetaEle);
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G4double dxPos=-std::sin(thetaPos)*std::cos(phi),dyPos=-std::sin(thetaPos)*std::sin(phi),dzPos=std::cos(thetaPos);
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// Kinematics of the created pair:
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// the electron and positron are assumed to have a symetric angular
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// distribution with respect to the Z axis along the parent photon
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G4double electronKineEnergy = std::max(0.,electronTotEnergy - electron_mass_c2) ;
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// SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
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G4ThreeVector electronDirection (dxEle, dyEle, dzEle);
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electronDirection.rotateUz(photonDirection);
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G4DynamicParticle* particle1 = new G4DynamicParticle (G4Electron::Electron(),
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electronDirection,
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electronKineEnergy);
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// The e+ is always created (even with kinetic energy = 0) for further annihilation
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G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
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// SI - The range test has been removed wrt original G4LowEnergyGammaconversion class
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G4ThreeVector positronDirection (dxPos, dyPos, dzPos);
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positronDirection.rotateUz(photonDirection);
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// Create G4DynamicParticle object for the particle2
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G4DynamicParticle* particle2 = new G4DynamicParticle(G4Positron::Positron(),
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positronDirection, positronKineEnergy);
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// Fill output vector
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// G4cout << "Cree el e+ " << epsilon << G4endl;
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fvect->push_back(particle1);
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fvect->push_back(particle2);
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// kill incident photon
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fParticleChange->SetProposedKineticEnergy(0.);
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fParticleChange->ProposeTrackStatus(fStopAndKill);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4LivermoreGammaConversionModelRC::ScreenFunction1(G4double screenVariable)
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{
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// Compute the value of the screening function 3*phi1 - phi2
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G4double value;
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if (screenVariable > 1.)
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value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
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else
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value = 42.392 - screenVariable * (7.796 - 1.961 * screenVariable);
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return value;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double G4LivermoreGammaConversionModelRC::ScreenFunction2(G4double screenVariable)
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{
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// Compute the value of the screening function 1.5*phi1 - 0.5*phi2
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G4double value;
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if (screenVariable > 1.)
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value = 42.24 - 8.368 * std::log(screenVariable + 0.952);
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else
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value = 41.405 - screenVariable * (5.828 - 0.8945 * screenVariable);
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return value;
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}
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