Re: [fluka-discuss]: role of RADDECAY in scoring isotope yields

From: Anna Ferrari <>
Date: Mon, 21 Apr 2014 20:38:44 +0200

Dear Marco,

it is not suprising that you find a such difference between the residual
scored via the usrrnc user routine and those scored via RESNUCLEI:
- in the first case you score all the residual nuclei that are produced by the
prompt radiation in the region/detector you have selected, *without* taking
into account their decays;
- in the second case, if via the RADDECAY card the radioactive decays in
semi-analog mode are activated, you score the residual nuclei at the end of
the event tracking: each radioactive nucleus is treated like all other
unstable particles with a pure Monte Carlo method (random decay time,
daughters and radiation; all secondary particles/nuclei carry time stamp
['age'] ). You are observing therefore the effect of the decays.
If you switch off RADDECAY, RESNUCLEI gives you exactly the same results as
usrrnc, because you count only the residual nuclei produced by the prompt
The answer to your last question:
>Question: is there some parameter that I need to change in order for usrrnc to take into account radioactive decays?

is no (as far as I know...): you must go through RADDECAY to take into account
radioactive decays.
Hope it helps,
kind regards,

Am Fri, 18 Apr 2014 16:37:29 +0800 schrieb "Marco Grassi (马酷)"
> Dear Fluka experts,
> my simulation setup consists in a single muon crossing a sphere filled with
>liquid scintillator (basically a carbon+hydrogen compound) and my goal is to
>score the isotope yield on an event-by-event basis.
> To this purpose I'm using usrrnc.f (USERWEIG).
> At the same time I use the RESUCLEI output (what(2)=22) to crosscheck the
>overall run yield.
>Following the manual suggestion, I activated radioactive decays in
>semi-analogue mode by adding RADDECAY to my input file (you can find the
>input file attached to this message).
> My issue is that, using the aforementioned configuration, the isotope yields
>scored via usrrnc often exceed those scored via RESUCLEI (cf.
> So far, I managed to score the same number of isotopes in usrrnc and in
>RESUCLEI only by removing the RADDECAY option from my input file (that is
>clearly something that I don't want to do).
> Question: is there some parameter that I need to change in order for usrrnc
>to take into account radioactive decays?
> Thanks
> Marco

Anna Ferrari
Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf e.V.
Tel. +49 351 260 2872

Prof. Dr. Dr. h. c. Roland Sauerbrey, Prof. Dr. Dr. h. c. Peter Joehnk
Vereinsregister: VR 1693 beim Amtsgericht Dresden
Received on Mon Apr 21 2014 - 21:37:32 CEST

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