Dear Fluka experts,
I am simulating 5.5 MeV alpha on Be target for the evaluation of cross section in units of mb/MeV/sr. I find that the evaluated data is way too high as compared to experimental and PHITS data, although the peak position matches. Whereas for 6.5 MeV, the FLUKA, PHITS and the experimental data matches well. I have carried out the simulation with both ENDF and JEFF data set and both are giving the same results. I am attaching the data plot and the input file for 5.5 MeV for reference.
A few remarks after a first glance, assuming all the while that the main channel for neutron emission is 9Be(a,n) at your energies:
In your plots I do not see the experimental data you refer to. Could you provide them?
The partial cross section for the 9Be(a,n) channel appears to stay roughly constant for alphas of 5.5 MeV (~570 mb) and 6.5 MeV (568 mb), looking e.g. at EXFOR data:
Under these conditions (integrating over all outgoing neutron directions and energies) we observe offline that the FLUKA integrated cross section is actually ~40% lower than the EXFOR data for 6.5 MeV alphas and ~25% lower for 5.5 MeV alphas.
The above discussion of course pertains to a quantity integrated over all outgoing neutron directions and energies. You are instead resolving in energies (not a problem) and looking at ~5 deg window around ~60 deg. If you have exp data matching these settings, we’d indeed be interested in looking at them (it would be very surprising to see the angular distribution squeeze so much in this angular domain to locally compensate for the findings of the previous paragraph).
A couple closing remarks.
In your beam card you’ve put Rmin=0.15 and Rmax=0. You possibly intended to have the conjugate setting.
I have carried out the simulation with both ENDF and JEFF data set and both are giving the same results.
The likelihood for the generated neutrons to scatter or interact on the way out of your ~10 um slab is fairly small. Thus, the neutron interaction treatment (pointwise using this or that library) should not really matter.
