Simulating radioactive decay of only the mother nuclide

Continuing the discussion from Simple Test for H*(10) returns weird output for Am-241:

Hello FLUKA users,

the above mentioned thread answered how I used the semi-analogue decay mode in the wrong way or why the results differed from what I expected.
But the question I am left with right now is: How am I able to only simulate the mother nuclide or for realism the mother and the short lived daughters?

Best Regards, Tim

Hi Tim,

What you can do in this case is setup a time cutoff, so that any particle stops being transported after that set time.

In the case of an ISOTOPE source, the primary (decay product) is created with a time already set at the sampled decay time, which means the time cutoff can be used to remove those products that are coming from long-lived isotopes, thus reproducing somewhat a DCYTIMES philosophy (which as a reminder is not available for ISOTOPE sources)

In this particular case, we are lucky, as the half life of 241Am is much shorter than that of its daughter. You can then “isolate” 241Am decay products by setting a time cutoff at a few times 241Am half-life. This is done through the addition of the TIME-CUT card.
Please see TIME-CUT in the manual for the syntax, and be mindful of the fact time is expressed there in nanoseconds


Hi Philippe,
I have only now found the time to look at the TIME-CUT card and test it. My understanding is that in my case I only need to use What(1) and What(4) like

What(1) to give the cutoff-time in ns
What(4) to put in Ray (0), so the time-cutoff will be applied to every particle

I added it to my input given in the other thread and the result does not change for the suggested cutoff-time of 10-20 times 241Am half-life. I am looking for a cutoff-time now that fits to what I expecting.

Cheers and thanks for your help!

Hi Tim,

That is correct, however, I do not think defaults work in this case. I have specified “all particles” manually:

yielding the following (before/after cut)

1 Like

The default (WHAT(4)=0=empty and WHAT(5) empty, as WHAT(6)) applies the cutoff to all particles whose ID number is larger than 0, thus excluding alphas, which are instead included in @pschoofs card.

Thank you both for clarifying that and sticking with me here!