Dear FLUKA experts,
I am running a testing setup to see how FLUKA handles imported energy spectra sampling, following instructions on this page: Sampling from energy spectra. However, I found it a bit confusing for me to understand how this sampling works unit wise. According to what this says, Sampling from energy spectra, it doesn’t matter what unit I choose for the external spectra. However, I found it is not the case when I run my setup.
In my setup, I am shooting proton beam through vacuum while setting an USRBDX estimator right in front of the source. Now, if everything works as the guideline indicates, no matter what unit I choose for my source, the spectra generated by USRBDX should look the same and also same as the input external spectra if I convert everything into the same unit. Therefore, I tried 2 different input spectra to test this. First, I used probability as my 3rd column arguments for the external spectra file, which is unit-less of course (or part/pr). Then, I converted the probability into fluence, dividing it by the area of the detector and then the bin width. Now, the 3rd column should have (part/pr/cm^2/GeV) as unit. Yet, the spectra generated by USRBDX is not the same for these two runs. What did I do wrong?
The attached is my input file and the external energy spectra (The 3rd column is probability not fluence for this file) for the setup if you want to take a look.spectra_sampling.inp (1.2 KB) TSP.txt (1.8 KB)
Thanks in advance.