Iron fluorescence

Dear FLUKA experts,
I am trying to simulate simple Iron fluorescence spectra from 10 Kev photons.
my object is 25 micron iron sheet.
I used USRBDX as my detector, and the only peak that appears is the 10 Kev.
From the manual I understood that different defaults should be set,
but I was not able to achieve the typical peaks of the iron.

How should I set the defaults?

Thank you in advance,
Hen Shukrun

Dear Hen,

You can leave the PRECISIOn defaults in your problem, and consider the following:

  • Without having seen your input file, one can only make a reasonably educated guess: the fact that you just see the 10 keV peak in your USRBDX plot suggests you may be scoring 2-way fluence and just scoring the photons incoming from vacuum into the target (which should be killed immediately, being below the default threshold of 33 keV).

  • You will have to issue two EMFCUT cards: one to lower the photon transport threshold and one to lower the photon production threshold from their default values of 33 keV to, say, 1 keV. FLUKA will complain if you leave empty values for the corresponding electron thresholds. One should in principle put correspondingly low electron thresholds. However, assuming that you’re interested in the fluorescence spectrum only (and not on energy deposition), and considering that FLUKA does not have a detailed model for direct inner-shell ionization by electron impact, you can exceptionally leave high electron thresholds (10 keV is high enough in your problem). This will considerably speed up the simulation. Incidentally, if you observe minor mismatches between simulated and experimental fluorescence line intensities, the aforementioned lack can be among the causes. Do keep in mind that if later you care about energy deposition, you should absolutely lower the electron thresholds and gracefully tolerate any increase simulation time.

  • For good measure, in your USRBDX you should be mindful of selecting the one-way fluence (ending in “1” instead of “2” in the corresponding Flair drop-down menu) from your Fe target back into the surrounding vacuum/air.

Hoping this helps,