Missing High-Energy Neutron Fluence Peak in USRBDX Spectrum

Scoring
1

Versions

Please provide the used software versions.

FLUKA:4.5.0
Flair:3.4.3

Description

Dear Experts,

I am currently working on calculating the neutron energy spectra resulting from 215 MeV protons impinging on a iron target. Specifically, I am interested in obtaining the Fluence(cm^-2 sr^-1 per primary) as a function of energy within an angular range of 0–15°.

To achieve this, I am using USRTRACK to score the fluence within the region and USRBDX to score the fluence at boundary. However, the resulting spectra do not show the expected high-energy neutron fluence peak, which is typically observed, as described in Scoring_II_Differential_spectra for forward angle, slide 13. The peak is either missing or significantly suppressed in my results.

I have attached the input file for your reference. I would greatly appreciate any guidance on how to resolve this issue and ensure that the high-energy component is correctly captured.

Thank you for your time and support.

scoring_60_plot
scoring_60_plot640×480 51 KB

Best regards,

Input files

scoring.inp (1.7 KB)
scoring.flair (1.2 KB)

Please upload all relevant files. (FLUKA input file, Flair project file, user routines, and data files)

3

Dear Rahil,

thank you for your question and for the input file, but is this the same input you used to obtain the plot you are showing?

The doubts I have relate to:

  • You are interested in the neutron spectrum coming from a 215 MeV proton beam impinging on a Fe target. But in the input, the proton has an energy of 250 MeV and the target is made of Cu.
  • With USRTRACK you cannot score the double differential distribution of neutrons. You can do it with the use of USRBDX as you are already correctly doing.
  • In the plot you show, the title says proton ion 215MeV on tissue target, so is this a neutron or proton spectrum?
  • Looking at the example in the scoringII lesson, in slide 13, a spectrum of HAD-CHAR is shown (therefore clearly not including neutrons) for a proton beam of 3.5 GeV impinging on a water+Al+Pb target. I don’t think you should use this as guidance for your results.

I suggest to try the exercise related to the scoringII lesson to understand the settings needed to obtain your desired quantities and the different approaches you can use.

Best,
Giuseppe