Re: [fluka-discuss]: Prompt Gamma Spectrum SImulation

From: Paola Sala <>
Date: Thu, 25 Mar 2021 12:30:42 +0100

Dear Pierfrancesco
in your input you are using a low energy neutron beam. Fluka transports
neutrons below 20 MeV with a groupwise algorithm (see the manual for
details).With this method, photons from in neutron captures and
interactions are also produced in energy "groups", not as discrete gamma

Thus, you should see no lines at all.

Indeed, what you see in your detector are statistical fluctuations, except
the 511 keV line from positron annihilation. Indeed,looking at the tab.lis
or sum.lis file you'll notice the very large statistical errors.

If you push your statistics, say a factor 10 better, you will get a smooth
spectrum plus the 511 line. I attach the plot I obtain (with a cut on the
max value) , however selecting a fixed neutron energy as beam because I do
not have your source.f and the datafile.

Besides this, in the input file there is no DETECT card, rather a USRTRACK
card, which has a different meaning: DETECT scores deposited energy,
USRTRACK scores particle fluence vs energy

I also see that you added a raddecay card. With this card, one can get
gamma lines (lines this time) from radioactive residual nuclei. However,
to include them in the scoring, one has to issue DCYSCORE cards for the
estimators concerned.

Hope this helps

> Dear Expert and FLUKA Users,
> I'm tring to obtain a Prompt Gamma Simulation Spectrum from a sample of
> Fe and Cu using a Ge Detector.
> I'm able to obtain the spectrum using the DETECT card, that shows the
> sharp peaks as expected.
> The problem is that the peaks are not in the positions reported in the
> database (as IAEA PGAA Database).
> The intensities are not respected.
> Can someone help me to understand why this happens?
> I'm attaching my INPUT File and the resulting Spectrum.
> Thank you !
> Pierfrancesco

Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148

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Received on Thu Mar 25 2021 - 14:46:20 CET

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