Gabriele Cosmo
107 lines
4.2 KiB
Plaintext
107 lines
4.2 KiB
Plaintext
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Geant4 Isotope Production Models
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--------------------------------
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As of January 2012, the use of the isotope production models had been
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largely superseded, as most inelastic models automatically place the
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residual nucleus on the final state stack where it is readily available
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to users. Exceptions are the Low Energy Parameterized (LEP) models
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which do not create residual nuclei. As a result, the isotope
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production models are now used only in conjunction with the LEP models,
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and the infrastructure for isotope production has been moved from the
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process level (G4HadronicProcess) to the model level
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(G4InelasticInteraction).
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Physics List
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------------
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As before, isotope production can be invoked from the physics list, but
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with some changes. To enable isotope production, your physics list must
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have the following lines:
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for neutrons:
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if (particleName == "neutron") {
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G4NeutronInelasticProcess* theInelasticProcess =
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new G4NeutronInelasticProcess();
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G4LENeutronInelastic* theLEInelasticModel = new G4LENeutronInelastic;
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// Turn on isotope production
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theLEInelasticModel->TurnOnIsotopeProduction();
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G4NeutronIsotopeProduction* aProductionModel =
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new G4NeutronIsotopeProduction();
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// Assign a specific model to handle production
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theLEInelasticModel->RegisterIsotopeProductionModel(aProductionModel);
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theInelasticProcess->RegisterMe(theLEInelasticModel);
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pmanager->AddDiscreteProcess(theInelasticProcess);
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}
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The line
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theLEInelasticModel->TurnOnIsotopeProduction();
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activates for the neutron inelastic model the generic isotope production
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based on the incident particle, target nucleus and produced secondaries.
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It is valid for all incident energies, but does not take into account the
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detailed production cross sections found, for example, in G4NDL.
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If you have an improved model, for example G4NeutronIsotopeProduction,
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it can be added in the subsequent lines:
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G4NeutronIsotopeProduction* aProductionModel =
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new G4NeutronIsotopeProduction();
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theLEInelasticModel->RegisterIsotopeProductionModel(aProductionModel);
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Within its energy range of validity, this model will now override the
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generic model. Outside that range, the generic model again takes over.
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The G4NeutronIsotopeProduction model depends on the G4NDL database so you
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must set the environment variable G4NEUTRONHPDATA to point to it.
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A similar procedure must be followed for each low energy parameterized
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model you wish to enable for isotope production, for example
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G4LENeutronInelastic
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G4LEProtonInelastic
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G4LEPionPlusInelastic
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...
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...
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Currently Geant4 provides only one detailed isotope production model that
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applies to incident neutrons, as well as a prototype for protons. Others
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must be developed by users.
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Stepping Action
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---------------
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The user's SteppingAction must also be modified to include the headers
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#include "G4IsoParticleChange.hh"
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#include "G4InelasticInteraction.hh"
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and to add some output lines to
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void MySteppingAction::UserSteppingAction(const G4Step* theStep).
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An example would be:
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G4String procName =
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theStep->GetPostStepPoint()->GetProcessDefinedStep()->GetProcessName();
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if (procName == "NeutronInelastic" || procName == "ProtonInelastic") {
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// Look only when neutron or proton initiated the isotope production
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G4IsoParticleChange* isotopeProdInfo =
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G4InelasticInteraction::GetIsotopeProductionInfo();
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if (isotopeProdInfo) {
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// Be sure that an isotope was created
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G4cout << " Production model: " << isotopeProdInfo->GetProducer() << G4endl;
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G4cout << " target nucleus (A,Z) : "
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<< isotopeProdInfo-> GetMotherNucleus().GetA_asInt() << " , "
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<< isotopeProdInfo-> GetMotherNucleus().GetZ_asInt() << G4endl;
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G4cout << " produced isotope: " << isotopeProdInfo-> GetIsotope() << G4endl;
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G4cout << " production time: " << isotopeProdInfo->GetProductionTime() << G4endl;
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G4cout << " parent particle: " << isotopeProdInfo->GetParentParticle()->GetParticleName()
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}
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}
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