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

From: Marco Grassi (马酷) <"Marco>
Date: Tue, 22 Apr 2014 11:12:19 +0800

Dear Anna,

thanks a lot for clarifying this issue. But now I have a doubt about the way RADDECAY works.

Let's assume that RADDECAY is active in semi-analogue mode. When I see an isotope in the RESNUCLEI score, it
means that it didn't decay during the time window assumed for the MC simulation. E.g. 9Li (one of the isotopes
I'm interested in) has a ~180ms half life. If the simulated time window was 5 seconds long, I should see no
9Li left in the detector, hence no Li9 in the RESNUCLEI score.

My impression is that the isotope yield that RESNUCLEI is scoring might be strongly dependent on the time
window assumed by RADDECAY. Is this correct?

If this is the case, can you please quantify the length of such a time window?

Thanks again,

On 22/4/14, 2:38, Anna Ferrari wrote:
> Dear Marco,
> it is not suprising that you find a such difference between the residual nuclei
> 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 radiation.
> 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,
> Anna
> 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
> Vorstand:
> Prof. Dr. Dr. h. c. Roland Sauerbrey, Prof. Dr. Dr. h. c. Peter Joehnk
> Vereinsregister: VR 1693 beim Amtsgericht Dresden
Received on Tue Apr 22 2014 - 06:23:44 CEST

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