[fluka-discuss]: Problem(?) with secondary protons and neutrons after alpha interaction with aluminum

From: Ivan <gordeev_at_jinr.ru>
Date: Tue, 18 Dec 2018 18:10:06 +0300

Dear FLUKA experts!

I have a problem or misunderstanding in work. I have a geometry -
cylinder H = 12m, D = 6m, with air inside and aluminum shell 5.55 cm
thick (see attached input file). And from the sphere of 7m diameter
inside the sphere alpha particles emitted with fluence spectrum
(attached user source routine and spectrum) in case that inside will be
uniform and isotropic fluence of these particles with value 1/(pi*R^2).
So, in the output secondary proton spectrum inside cylinder, I have a
"fall" starting from about 100 MeV and up to about 400 MeV and same
picture for neutrons, I found this confusing, because I have results for
the same task from MCNPX and it is about the same for alpha inside, but
protons and neutrons spectra are smooth and without these "falls". I
just cant believe that physics models can be so different and cause this
"fall" in spectra and also, I am also not sure about my source routine
and I tried everything with physics, it seems like I don't have a clue
now. Also, before this task I did the same, but emitting protons on the
cylinder using the same way and output fits with the results from MCNPX
pretty well.

Please help! I am new using FLUKA and seems lack of ideas now...
Attached: input file, source routine, spectrum, output files (23 -
protons, 24 - neutrons, 27 - alpha), figures of "fall" for protons and

Thanks in advance!
Best regards,
Ivan Gordeev

P. S. Sending this for the third time, just don't know if it is sent or

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(image/png attachment: Neutrons.png)

(image/png attachment: Protons.png)

Received on Tue Dec 18 2018 - 17:23:16 CET

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