|Message: Strange behaviors of the NeutronHPInelastic process using Lithium||Not Logged In (login)|
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I am currently testing the Geant4 code for fusion neutronic application, which is seldomly done before. I got very strange result for isotopes Li-6 and Li-7, which have very large differences with MCNP and FLUKA results.|
I use a very simple geometry, a sphere with R=30cm, assuming its volume is 1 cm3. And a use a point source at the center of the ball with initial energy 14.1 MeV. The material I used is one pure isotope. H-1, Li-6, Li-7, Be-9 and Cnat is tested, with density assuming 1.0 g/cm3.
I made the flux score myself by accumulating the neutron track length inside the sphere, and divided into 260 energy bins. And the flux spectrum is obtained by Flux density / ∆E. In these calculations I used Geant4 10.0.0 and GNDL4.4.
I found that the H-1 results are quite satisfied. Result for Be-9 and Cnat is OK except larger differences in low energy range. But when I got the Li-6 and Li-7 results I was very disappointed. The differences are very significant. I suspected the neutron cross section in GNDL so I extract the GNDL cross section and make comparison with ENDF/B-VII.0 library from t2.lanl.gov, but it looks the same.
I found that results for isotopes H-1, Cnat, Be-9 which elastic scattering cross section is dominant are quite agree with MCNP and FLUKA. Therefore in my code I make only the NeutronHPInelastic process available and comment out others, and I got very strange result for both Li-6 and Li-7. The figure is attached with this post.
Li-6 inelastic cross section has a resonance peak in ~0.25 MeV, therefore the flux should have a pit-fall at this energy point. But it did not happen. The most strangest thing is, Li-6 and Li-7 result is coincident in this case! But they have totally different inelastic cross section.
Therefore, I am questioning the NeutronHPInelastic process, whether it performs correctly. Because we would like to explore Geant4 for fusion application, the Lithium is extremely important for our calculation. I hope there are somebody can help me to have a check on this process.
PS. I could not attach the code. you can find it with this link: https://drive.google.com/file/d/0B7GSavXztMOuVDBuaHFJQ3pEc3M/edit?usp=sharing
For checking the ENDF/B-VII.0 cross sections, please follow this link: http://t2.lanl.gov/nis/data/endf/endfvii-n.html.
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