Double differential neutron yield

Flair
1

Versions

FLUKA: 4-5.0
Flair: 3.4-3

Description

Dear Fluka experts,

I’m just starting to learn how to use Fluka. Currently, I’m using Fluka to calculate the double differential neutron yield from heavy-ion bombardment of a lead target. I selected the USRYIELD card in Flair to record secondary neutrons emitted at different angles. Here are my questions:

1. I’m unsure if my input cards are correct. Specifically, for the yield parameter in the USRYIELD card, options include EMERGING and ENTERING. Despite consulting the Fluka manual, I don’t understand what these options mean. In my input cards, I haven’t selected either option.

2. During the calculation, I set the particle count to 10000, spawn=100, and cycle=5. Is the total particle count 1000×100×5=5e5? I want to divide the final result by the incident particle count to obtain units of neutron/sr/MeV/ions. Are the units of the result calculated by Fluka: neutron/sr/GeV/ions? If not, should I divide the result by 5e5?

Thank you very much in advance for your help!

Input files

BePb_500MeV.flair (14.6 KB)

3

Hello @liq, welcome to the FLUKA forum!

To answer your questions:

  1. In your USRYIELD card, when you select “EMERGING” you will score the distribution of neutrons when they are created, i.e., when the inelastic hadronic interaction occurs that produces it. On the other hand, when you select “ENTERING”, you score the distribution of particles which trigger the inelastic interactions, i.e., the particles that cause it to happen. If you choose neither but just leave it blank you will calculate the neutron yield on the surface boundary going from your TARGET to VOID regions. If you like you can further consult on this topic in this post on particle yields or in this post on a spallation neutron source.
  2. Considering you choose indeed the last case: in FLUKA results you obtain are always expressed per primary particle. So in your case you obtain a result in units of neutrons/sr/GeV/ion (so GeV, not MeV!).

Let us know if you run into any other issues,
Cheers,

Andreas

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