When using a spectrum (2H.txt), which is basically a reference spectrum (cpa2.txt) with increased values in specific bins (quite alot between 1-3 MeV and only a little in 5MeV region), the USRBDX scoring (in this case protons from source entering the target) shows quite unexpected differences between these two source beams, opposite to what I would expect.
Why the USRBDX response for red spectrum (>3 MeV) is lower than in blue, even though the values for high energies are bigger? Why values for ~2MeV are not 2 times bigger, even though the value in the file is? Is there any way to account properly for that? I’ve looked into the readme file, but I’m not sure if biasing can help here.
TL;DR version:
I’ve increased amount of particles by a factor x2 around 2 MeV, but it’s not visible during scoring.
you need to keep in mind, that FLUKA results are normalized to 1 primary particle, meaning the integral of spectrum is equal to 1.
You need to normalize both spectrums separately, according to their absolute intensities.
I am not sure that I understand your suggestion. What do you mean by “normalize separately”?
I’d like to stress that the image I’ve uploaded shows only the energy spectra, defined by text files, of source scored at the entrance to the target, not the actual output of source beam interaction with the target. So basically, my issue is that the sampling doesn’t reflect the original experimental spectrum I’ve tried to recreate in FLUKA simulation.
This is the result that I’d like to obtain (I’ve plotted the data in provided files using gnuplot, low edge of bins (column 1) and the relative intensity (column 3)).
I see! So to sum up - when I’ll be using these two inputs and would like to compare results of these beams interacting with anything, I have to normalize any end results by the ratio of the intensities? In this case, for the “2H” spectrum, everything that involved this source has to be normalized by a factor of ~1.27 ( which is the result of 1732/1368) when comparing to results obtained with “cpa2” spectrum - am I correct?
exactly, you need to normalize your results. If you are only interested the ratio between the two beams, it is enough to multiply the 2H results with ~1.27. However, if you are interested in real beams, then you need to multiply the results with their total intensity.
