I have been looking into scoring an activation reaction within a FLUKA simulation. The reaction itself is a 19F(n,alpha)16Na. I’ve tried scoring it with a USRBIN card, a USRYIELD card and with RESNUCLEI. All of them are giving back zero. Thus, I belive there must be something wrong with the physics definition cards. I made sure to turn on radioactive decay, ion transport and low-energy neutron transport with pointwise treatment, but it still does not work. Here is an image of the physics and scoring cards.
The rest of the simulation is pretty straightforward: a plastic material containing 19F and the neutron beam right in front of it with an energy of 3MeV.
Hallo Joaquin,
I guess you meant 16N, and not 16Na.
Actually, there are many issues in your input:
It looks like you are not using a compatible Flair version (not sure about the FLUKA one);
In the USRYIELD card, you are asking for alpha particles … of zero charge, which obviously you cannot find;
In the USRBIN card, you are asking for fluence of alpha particles that - in the associated AUXSCORE - are required at the same time … to be neutrons, which also can only produce a zero result;
RADDECAY is irrelevant, since your alphas come from a prompt reaction and not from a late decay of a radioactive product;
LOW-NEUT and LOW-PWXS are useless, since low-energy neutron pointwise treatment is activated by default;
PART-THR is ineffective, since you input a value below the minimum acceptable;
LAM-BIAS does not apply to low-energy neutrons.
Still, the fact that you do not observe any alpha in RESNUCLE or in the output file (in the SCORE table) may simply mean that your statistics is not enough, in view of your geometry and the concerned reaction cross section.
Please upload a full (compatible) input file in case of persisting trouble.
Yes indeed I meant 16N.
Every problem is very clear, I made those corrections and now it is working perfectly, thank you very much.
However there is one thing regardin the use of the AUXSCORE card that I do not fully understand.
As for the example found in the documentation:
The scored quantity (in this case the energy) is filtered by the AUXSCORE to only take the energy deposited by protrons. Thus, when I used it my thought was that I would be scoring the 4He particles produced by neutron interactions, thus scoring the number of (n,alpha) interactions. Is there a way to achieve that?
Thank you.
Cheers!
Joaquin
I think I have found my mistake, I’ve been doing it the other way around. What I need to score the number of (n,alpha) interactions is a USRBIN card with WHAT(2) = NEUTRON followed by an AUXSCORE with WHAT(2) = 4-HELIUM. That way the USRBIN card scores the density of stars produced by neuitrons, and then the AUXSCORE card filters those stars to only count the alpha particles. Is that right?
Thanks!
Joaquin
The manual’s example you report (where we have a typo: the AUXSCORE card has MUONS and we erroneously write protons in the comment) is substantially different from your case. There, the energy deposition scoring is filtered by the type of the particle currently transported. In your case, if you score alpha or neutron fluence, the identity of the particle currently transported is already determined. The same if you score alpha or neutron star density (that is a more exotic option offered by USRBIN too).
I’d simply score transported alpha fluence with USRBIN, without AUXSCORE, and stopping alpha yield with RESNUCLEi.
Then, the entry USDRAW of mgdraw[_empty].f allows you an event-by-event interception of the reaction of your interest.
