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Question gamma emission from inelastic scattering of fast neutrons on C nucleus 

Keywords: gamma emission, inelastic scattering of fast neutrons
Forum: Particles
Date: 20 Sep, 2006
From: Corinne Groiselle <Corinne Groiselle>


I'd like to simulate the gamma emission resulting from the inelastic scattering of fast neutrons (14.1 MeV) on

carbon nucleus (12C). To do so, I've added a G4HPorLEInelasticModel instance in the inelastic process manager

attached to the neutrons particles.

As a result, I get the distribution of the emitted gamma, which, in my mind, should be more or less exclusively

made of 4.3 MeV carbon ray.

The problem is that, in addition to this ray, I also get some other peaks, corresponding to other carbon

nuclear excitation states, but with an intensity much higher than predicted (wrt nuclear database and MCNP simulations).

I tried to change the neutron inelastic model (NeutronHPorLEInelastic, Precompound, Bertini), as well as using

the LHEP_PRECO and LHEP_PRECO_HP physics list. I also verified that the G4NDL and the PhotonEvaporation

data are readable and are well pointed out by environment variables.

The results are very different from a model to another, but although the 4.3 MeV peak is always present, there is

always other peaks or continuous spectrum superimposed to this 4.3 MeV peak.

For exemple, if I use LHEP_PRECO_HP or my own physic list, where only NeutronHPorLEInelastic process is set (plus transportation),

I obtain the 4.3 MeV peak, but also 4 others peaks (namely, the 8.268, 9.637, 12.703 and 15.100 MeV peaks)

with intensities largely higher than expected.

So, my question is : does anybody already encountered this kind of problems or have a tip to help me with it ?

A possible reason would be that I don't plot only the gamma emitted from neutron inelastic interaction.

To get this spectrum, I've wrote a G4UserTrackingAction, where I record the kinetic energy of track if and only if

the track particle is a photon (PDG=22), the volume is the carbon target, the parent is track 1 (corresponding to

the 14.1 MeV neutron), and the process is "NeutronInelastic". Do you think I'm doing something wrong in this step ?

Thank in advance for any of your suggestions...

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