Dear Sandipan,
I played with your input file and noticed two things:
1. The LOW-MAT card is unnecessary with pointwise transport, since the
cross sections are defined by the LOW-PWXS card parameters (and by TSL-PWXS
for thermal neutrons in case their accurate transport is required).
2. The WHAT(1) card of LOW-PWXS should be set to 1 in your case. This
allows FLUKA to automatically map the material isotopes to pointwise
cross-sections.
That value was not set in your input file, so the code used groupwise
transport, where delayed neutrons are not produced.
Since the delayed neutron fraction is very small compared to the prompt
component, it might be tricky to observe statistically significant
difference using your USRTRACK estimator, therefore I added two USRYIELD
cards to score the time and energy spectra of neutrons escaping the target
region.
These spectra are shown in the right pads of the attached image, clearly
revealing the delayed neutron contribution, which disappears when the
delayed neutron production is disabled.
Best,
Konstantin
Il giorno gio 8 mag 2025 alle ore 21:31 sandipan <sandipan_at_barc.gov.in> ha
scritto:
> Dear FLUKA Team,
>
> Many thanks for releasing FLUKA2025.1.0 major iteration with lots of
> powerful capabilities.
>
> I was exploring the delayed neutron production feature in the released
> version for a test input made up of U235 with thermal neutron as
> incident beam. I have used the PHYSICS card with Delayed Neutron option
> and RAD-DECAY card in analogue mode. But the .out file does not score
> any delayed neutrons though 19% of the low-energy neutron interaction
> shows fission. Am I doing anything wrong here? I would really appreciate
> if you can guide me.
>
> Furthermore, I would be interested in studying ratio of prompt neutron
> vs delayed neutrons and its variation with time after an irradiation of
> certain time for optimization of design of a Fission Chamber. Is it
> possible in the present version?
>
> Thanks in advance.
>
> Best
> Sandipan
__________________________________________________________________________
You can manage unsubscription from this mailing list at
https://www.fluka.org/fluka.php?id=acc_info
Received on Fri May 09 2025 - 20:50:49 CEST