Gabriele Cosmo
480 lines
15 KiB
C++
480 lines
15 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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// Author: Sebastien Incerti
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// 22 January 2012
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// on base of G4LivermoreGammaConversionModel (original version)
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// and G4LivermoreRayleighModel (MT version)
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#include "G4LivermoreGammaConversionModel.hh"
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#include "G4PhysicalConstants.hh"
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#include "G4SystemOfUnits.hh"
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#include "G4Log.hh"
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#include "G4Exp.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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G4int G4LivermoreGammaConversionModel::maxZ = 99;
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G4LPhysicsFreeVector* G4LivermoreGammaConversionModel::data[] = {0};
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G4LivermoreGammaConversionModel::G4LivermoreGammaConversionModel
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(const G4ParticleDefinition*, const G4String& nam)
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:G4VEmModel(nam),isInitialised(false),smallEnergy(2.*MeV)
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{
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fParticleChange = 0;
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lowEnergyLimit = 2.0*electron_mass_c2;
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verboseLevel= 0;
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// Verbosity scale for debugging purposes:
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// 0 = nothing
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// 1 = calculation of cross sections, file openings...
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// 2 = entering in methods
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if(verboseLevel > 0)
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{
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G4cout << "G4LivermoreGammaConversionModel is constructed " << G4endl;
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}
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4LivermoreGammaConversionModel::~G4LivermoreGammaConversionModel()
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{}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4LivermoreGammaConversionModel::Initialise(
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const G4ParticleDefinition* particle,
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const G4DataVector& cuts)
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{
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if (verboseLevel > 1)
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{
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G4cout << "Calling Initialise() of G4LivermoreGammaConversionModel."
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<< 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(IsMaster())
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{
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// Initialise element selector
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InitialiseElementSelectors(particle, cuts);
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// Access to elements
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char* path = getenv("G4LEDATA");
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G4ProductionCutsTable* theCoupleTable =
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G4ProductionCutsTable::GetProductionCutsTable();
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G4int numOfCouples = theCoupleTable->GetTableSize();
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for(G4int i=0; i<numOfCouples; ++i)
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{
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const G4Material* material =
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theCoupleTable->GetMaterialCutsCouple(i)->GetMaterial();
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const G4ElementVector* theElementVector = material->GetElementVector();
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G4int nelm = material->GetNumberOfElements();
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for (G4int j=0; j<nelm; ++j)
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{
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G4int Z = (G4int)(*theElementVector)[j]->GetZ();
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if(Z < 1) { Z = 1; }
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else if(Z > maxZ) { Z = maxZ; }
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if(!data[Z]) { ReadData(Z, path); }
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}
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}
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}
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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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void G4LivermoreGammaConversionModel::InitialiseLocal(const G4ParticleDefinition*,
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G4VEmModel* masterModel)
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{
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SetElementSelectors(masterModel->GetElementSelectors());
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double
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G4LivermoreGammaConversionModel::MinPrimaryEnergy(const G4Material*,
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const G4ParticleDefinition*,
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G4double)
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{
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return lowEnergyLimit;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4LivermoreGammaConversionModel::ReadData(size_t Z, const char* path)
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{
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if (verboseLevel > 1)
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{
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G4cout << "Calling ReadData() of G4LivermoreGammaConversionModel"
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<< G4endl;
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}
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if(data[Z]) { return; }
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const char* datadir = path;
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if(!datadir)
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{
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datadir = getenv("G4LEDATA");
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if(!datadir)
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{
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G4Exception("G4LivermoreGammaConversionModel::ReadData()",
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"em0006",FatalException,
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"Environment variable G4LEDATA not defined");
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return;
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}
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}
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//
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data[Z] = new G4LPhysicsFreeVector();
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//
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std::ostringstream ost;
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ost << datadir << "/livermore/pair/pp-cs-" << Z <<".dat";
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std::ifstream fin(ost.str().c_str());
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if( !fin.is_open())
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{
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G4ExceptionDescription ed;
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ed << "G4LivermoreGammaConversionModel data file <" << ost.str().c_str()
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<< "> is not opened!" << G4endl;
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G4Exception("G4LivermoreGammaConversionModel::ReadData()",
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"em0003",FatalException,
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ed,"G4LEDATA version should be G4EMLOW6.27 or later.");
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return;
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}
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else
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{
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if(verboseLevel > 3) { G4cout << "File " << ost.str()
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<< " is opened by G4LivermoreGammaConversionModel" << G4endl;}
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data[Z]->Retrieve(fin, true);
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}
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// Activation of spline interpolation
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data[Z] ->SetSpline(true);
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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G4double
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G4LivermoreGammaConversionModel::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 > 1)
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{
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G4cout << "Calling ComputeCrossSectionPerAtom() of G4LivermoreGammaConversionModel"
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<< G4endl;
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}
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if (GammaEnergy < lowEnergyLimit) { return 0.0; }
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G4double xs = 0.0;
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G4int intZ=G4int(Z);
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if(intZ < 1 || intZ > maxZ) { return xs; }
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G4LPhysicsFreeVector* pv = data[intZ];
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// if element was not initialised
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// do initialisation safely for MT mode
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if(!pv)
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{
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InitialiseForElement(0, intZ);
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pv = data[intZ];
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if(!pv) { return xs; }
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}
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// x-section is taken from the table
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xs = pv->Value(GammaEnergy);
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if(verboseLevel > 0)
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{
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G4int n = pv->GetVectorLength() - 1;
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G4cout << "****** DEBUG: tcs value for Z=" << Z << " at energy (MeV)="
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<< GammaEnergy/MeV << G4endl;
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G4cout << " cs (Geant4 internal unit)=" << xs << G4endl;
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G4cout << " -> first cs value in EADL data file (iu) =" << (*pv)[0] << G4endl;
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G4cout << " -> last cs value in EADL data file (iu) =" << (*pv)[n] << G4endl;
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G4cout << "*********************************************************" << G4endl;
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}
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return xs;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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void G4LivermoreGammaConversionModel::SampleSecondaries(
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std::vector<G4DynamicParticle*>* fvect,
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const G4MaterialCutsCouple* couple,
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const G4DynamicParticle* aDynamicGamma,
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G4double, 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 > 1) {
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G4cout << "Calling SampleSecondaries() of G4LivermoreGammaConversionModel"
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<< G4endl;
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}
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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 epsilon0Local = electron_mass_c2 / photonEnergy ;
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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 = epsilon0Local + (0.5 - epsilon0Local) * G4UniformRand();
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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 G4ParticleDefinition* particle = aDynamicGamma->GetDefinition();
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const G4Element* element = SelectRandomAtom(couple,particle,photonEnergy);
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if (element == 0)
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{
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G4cout << "G4LivermoreGammaConversionModel::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 << "G4LivermoreGammaConversionModel::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. * epsilon0Local / (element->GetIonisation()->GetZ3()) ;
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G4double screenMax = G4Exp ((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(epsilon0Local,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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do
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{
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if (normF1 / (normF1 + normF2) > G4UniformRand() )
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{
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epsilon = 0.5 - epsilonRange * std::pow(G4UniformRand(), 0.333333) ;
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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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} // End of epsilon sampling
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// Fix charges randomly
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G4double electronTotEnergy;
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G4double positronTotEnergy;
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if (G4UniformRand() > 0.5)
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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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// 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 = - G4Log(G4UniformRand() * G4UniformRand()) / a1 ;
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}
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else
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{
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u = - G4Log(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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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
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G4double positronKineEnergy = std::max(0.,positronTotEnergy - electron_mass_c2) ;
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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,
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positronKineEnergy);
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// Fill output vector
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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
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G4LivermoreGammaConversionModel::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 * G4Log(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
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G4LivermoreGammaConversionModel::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 * G4Log(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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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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#include "G4AutoLock.hh"
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namespace { G4Mutex LivermoreGammaConversionModelMutex = G4MUTEX_INITIALIZER; }
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void G4LivermoreGammaConversionModel::InitialiseForElement(
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const G4ParticleDefinition*,
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G4int Z)
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{
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G4AutoLock l(&LivermoreGammaConversionModelMutex);
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// G4cout << "G4LivermoreGammaConversionModel::InitialiseForElement Z= "
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// << Z << G4endl;
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if(!data[Z]) { ReadData(Z); }
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l.unlock();
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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