Dear fluka users
I am performing simulations with the radioactive neutron source. I want to score fluence of three energy groups; thermal energy, epithermal and fast neutron using USRBDX. I have set the energy intervals of interest but the program seems to ignore the upper energy limit because the spectrum appears to unexpectedly extend to 11 MeV energy.
I looked at Scoring certain range in results in USRBIN. However, I am not sure if I should follow the same procedure.
To better understand your problem, could you please share your .flair file?
Please find the attached .flair file and the spectrum used in simulation
ParaffinWax90.flair (5.0 KB) AmBe90.zip (838 Bytes)
in FLUKA the low energy neutrons (below 20 MeV) are treated with a multigroup algorithm.
See the relevant sections of the manual:
FLUKA will overwrite the scoring related to neutrons to match these groups:
It use the values from the scoring, (min,max energies and bin sizes), then it will cut off the part below 20 MeV and replace it with the fixed bins, down to the specified minimum energy (rounded down to match the fixed bin’s energy)
With this it is not necessary to score different part if the low energy neutron spectrum separately, only one scoring from thermal to 20 MeV is enough. If you are interest the number of neutrons in the different part, you need to manually process the output files.