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None Problem with Gamma,n reactions at low energies 

Forum: Hadronic Processes
Date: 19 Feb, 2014
From: Payam Pakarha <Payam Pakarha>

Hi, I have tried adding the (gamma,n) reactions to the physics list for 9Be atoms modifying G4PhotoNuclearProcess to add the cross sections manually. I'm basically using the suggestion from Andrew posted in: http://hypernews.slac.stanford.edu/HyperNews/geant4/get/hadronprocess/1326.html .

I managed to successfully compile the code and run it. However, I am observing an strange behavior. When I run the simulations using a macro which generates 1.83MeV gammas isotropically, I can see some neutrons at the outcome followed by the inelastic process (gamma,n) in the beryllium. But, similarly, when I generate the same energy gamma out of a radioactive decay of Y88, the neutrons are missing! Although, I checked that the source produces the gamma spectrum peaked at 1.83MeV.

Does it mean that somewhere in my physics list, the process is dependent on the creatorprocess additional to the particletype? Or, you think the problem might be somewhere else?

I added the method in my physics list like the following:

void XURI2PhysicsList::ConstructPhotoNuclearProcessBe() {

    G4ParticleDefinition* particle = G4Gamma::GammaDefinition();
    G4ProcessManager* pmanager = particle->GetProcessManager();
    G4PhotoNuclearProcessBe  *thePhotoNuclearProcess = new
G4PhotoNuclearProcessBe();
    G4GammaNuclearReaction *theGammaReaction = new G4GammaNuclearReaction();
    theGammaReaction->SetMaxEnergy(3.5*GeV);
    thePhotoNuclearProcess->RegisterMe(theGammaReaction);
    pmanager->AddDiscreteProcess(thePhotoNuclearProcess);

}

P.s: I tried so far to change my Geant4 from 4.9.6.2 to 4.9.5.2 and it didn't help. I also tried replacing the radioactive source with some other isotope above 1.8MeV and I see the same issue.

Thanks for your help in advance. Payam

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