Problem getting prompt gamma spectrum in PGNAA demonstration

I think I have the same problem described in the following post, could someone please confirm my suspicion:
Weird Gamma Spectrum in P+C reaction
If so, is there any future plan to make Fluka more “PGNAA friendly”?


I’m trying to demonstrate prompt gamma neutron activation analysis by directing
a beam of thermal neutrons at a silicon target (source files attached). The idea is
to view the prompt gamma peaks by plotting the energy spectrum of the gammas entering a target area. However, instead of getting nice sharp peaks where expected (e.g. 3539.0, 4934.0, 6379.8 and 7199.2 keV etc), I get rectangular columns all having widths of precisely 500 keV:
Any help fixing this problem would be most welcome,
Gary A.
PGNAAdemo.flair (3.1 KB) PGNAAdemo.inp (1.8 KB)

Hello Gary,

your output is the consequence of the multigroup treatment of neutrons below E < 20 MeV and their associated photons. Neutron induced photon emissions until E = 50 MeV are simulated within a coarse bin structure which does not resolve peaks.
Consult chapter 10 of the manual,
and in particular


Many thanks Thomas, I thought it might be so. Really appreciate your help,
Regards, Gary