Problem getting prompt gamma spectrum in PGNAA demonstration

Scoring
1

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”?

Details:

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:
PGNAAdemo
Any help fixing this problem would be most welcome,
Gary A.
PGNAAdemo.flair (3.1 KB) PGNAAdemo.inp (1.8 KB)

2

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, https://flukafiles.web.cern.ch/flukafiles/manual/10.html
and in particular https://flukafiles.web.cern.ch/flukafiles/manual/10.3.1.html

Thomas

3

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