Dear Fluka experts,
I am studying the photons emitted by a gamma energy source uniformly distributed in a rectangular volume (“Source” region). I want to count the photons reaching the outer surface of the detector.
So, I am using USDBDX card to score the one-way current of photons through the outer surface of the detector (between the “Envir” region and “Endcap” region) with energies 1-60 keV and any direction (one angular bin).
It seems that no photons reach the detector because the result is zero in every energy bin (sum.lis file). On the other hand, plotting USRBIN card, the fluence of photons seems to reach the detector.
However, I need some clarification:
I have not considered any normalization factor relating to the surface area crossed because I only want to count the number of photons. Looking at the plot you posted, the counts in the y axis are particle/GeV/pr. So If I need to obtain the number oh photons reaching the surfare with the energy of 1173 keV (the first peak of Co-60) I need to multiply for the energy bin and the number of primary generated in the simulation (1e4 in my case). Is it correct?
I had the doubt I wrote in the previus message because I remenber that when using a radioactive source with a semi-analogue option (as in my case), a primary would be a single decay. Probably, not in the case of USRBDX card.
In any way, I have the last question:
I changed the Co-60 source with a Am-241 source in a matrix of iron to simulate my worse case and verify if my detector see photons of low energy in a high Z material. Any other setting are unchanged. In the spectrum I obtained over the surface of the detector (current of photons throught detector endcap) energies higher than 59,54 keV are present. The Am-241 has other energies line between 60-100 keV but with a very low intensity. GSMS_full.flair (4.4 KB) GSMS_full.inp (3.6 KB)
As test, I repeated the simulation considering a beam of photons with energy of 59,54 keV instead of the Am-241 isotope. In this case, I see only the peak of 60 keV in the spectrum. GSMS_full_test.flair (4.5 KB) GSMS_full_test.inp (3.6 KB)
In your opinion, Is it something wrong in the simulation with the Am-241 isotope?
