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None Number of neutrons by fission, 2.37 | 2.64 in version 9.2.p02 | 9.3 with ParafissionModel+HPFissionData. 

Forum: Hadronic Processes
Date: 24 Mar, 2010
From: Quentin Cherel <Quentin Cherel>

Hi everybody

I found a little problem, or I have a little problem. The number of neutrons produced from a thermal fission of U235 changes dramatically from geant4 version 9.2.p02 to version 9.3, and doesn't seem correct in both cases.

I need to study the fission products so I have the ParafissionModel with the HPfissionData. Please note that when I use the HPFissionModel instead of the ParaFissionModel, I get the expected value of ~2.5.

for 10^5 incident thermal neutron on pure U235

4.9.3 Number of neutrons by fission : 2.64

4.9.2.p02 Number of neutrons by fission : 2.37

Here is the method I use to get the number of neutrons produced by a fission. I use the exact same application for both versions.

void MSteppingAction::UserSteppingAction(const G4Step* aStep)
{
  if(aStep->GetTrack()->GetDefinition() == G4Neutron::Neutron())
  {
	  const G4VProcess* process = aStep->GetPostStepPoint()->GetProcessDefinedStep ();

	  if (process->GetProcessName()=="nFission") 
	  {
		  G4TrackVector* secondariesTable = aStep->GetSecondary();	  
		  for ( unsigned int i=0;i<secondariesTable->size();i++)
		  {
			  if (secondariesTable[0][i]->GetDefinition() == G4Neutron::Neutron())
			  runaction->CountNeutronFission();
		  } 

	  }
  }

}

Here is the part of the physics list related to the fission process

 // Neutron-induced fission process, models and cross sections

G4HadronFissionProcess* neutronFissionProcess = new G4HadronFissionProcess();

		//LFission

G4LFission* theLFissionModel = new G4LFission();

theLFissionModel->SetMinEnergy(19.9*MeV);

theLFissionModel->SetMaxEnergy(20.0*TeV);

neutronFissionProcess->RegisterMe(theLFissionModel);

		//ParaFission

G4ParaFissionModel* theParaFissionModel= new G4ParaFissionModel();

theParaFissionModel->SetMaxEnergy(20.0*MeV);

G4NeutronHPFissionData* theHPFissionData=new G4NeutronHPFissionData();

neutronFissionProcess->AddDataSet(theHPFissionData);

neutronFissionProcess->RegisterMe(theParaFissionModel);

pManager->AddDiscreteProcess(neutronFissionProcess);

Cheers,

Quentin

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