Interactions of low energy neutrons traveling in a compound

Dear FLUKA experts,

I am trying to model a real-life neutron detector and I have encountered a lot of problems. Basically, I have a Pu-Be source put right in front of a steel canister which is coated with hexagonal Boron Nitride paint have a thickness probably around 10 microns on the inner surface and filled with Argon gas at 50 torr.

I examined my output file and find that no alpha particles were created even I switch the composition of paint to be purely Boron. What is the proper way to do what I’m trying to do?

The attached files are my input file and the energy spectra of my PuBe source.

Thanks in advance for the help and time.


BNTN.flair (2.0 KB) BNTN.inp (2.1 KB)
PuBe.txt (990 Bytes)

In general, the low energy (< 20 MeV) neutron treatment excludes the explicit production of charged particles at neutron interaction level (see the manual). Due to its importance, Boron is an exception, but, in order to get alphas and 7Li fragments as transported particles, you need to insert explicitly 10B in your material composition. This means that you have to define by means of a MATERIAL card a single isotope material called BORON-10 (with no need for an associated LOW-MAT card, since its name matches already the right one in the low energy neutron library). To do so, a mass number value of 10 has to be input in the proper MATERIAL field, which is WHAT(6) (A in Flair) and not WHAT(2) (Am in Flair). By the way, Am normally should not be filled, as clearly indicated in the manual.
Once you have your BORON-10 material, you may need to define also BORON-11, in order to build then with the two of them a B compound reflecting the natural composition. The latter will be eventually the ingredient of your final h-BN compound. At that point, you should be able to see alpha particles.

Dear @ceruttif,

Thank you for your time and the help. I read the manual but clearly did not understand it fully. I will follow your advice and try it again.