Re: low neutron

From: Anna Ferrari <>
Date: Tue, 17 Apr 2012 00:46:03 +0200

Dear Mojdeh Najm,

I tried to run your input.
Since you use the defaults NEW-DEFA, which enable the low energy neutron
transport, FLUKA checks if the low energy cross section tables are present for
every material. Since you have defined praseodymium, which has no library, it
stops. This happens independently on the fact that later on in the input you
swicth off the low energy neutron transport (I saw that you tried two methods:
to stop all the low energy transport via LOW-NEUT + PART-THR -as suggested in
the manual, note 2) under LOW-NEUT - or via LOW-BIAS, where you have put a
suitable group cutoff in the region that contains praseodymium). You can avoid
the problem with a trick (not elegant, but works). You associate your element
to an element whatever in the library: it is unphysical (I don't like it!) but
you will never use it. I tried to do like that and it works (pay attention:
what(1) in LOW-NEUT is the number of neutron groups in the cross section set
used... in your input it was wrong).
Maybe another approch is possible. You have a low-energy (around 2 MeV)
electron source... defaults EM-CASCA (defaults for pure EM) could be also
appropriate, you can give a look (there low-energy neutrons are obviously off
by default).
In any case I would suggest you to check your thresholds for the EM part: you
don't set them, then in the case of NEW-DEFA you get 1 MeV for electrons and
333 keV for photons, both for production and transport. Maybe you want to set
thresholds more appropriate for your low energy problem via EMFCUT.

Hope it helps,


Am Wed, 11 Apr 2012 02:26:01 +0430 schrieb mojdeh najm <>:
> Dear FLUKA experts
>> I set NEW- DEFAU with calling LOW-BIAS card but unfortunately I can not
>> achieve to complete run. I attached my input and flair files, what are my
>> input errors?
>> regards
> Mojdeh Najm
Received on Tue Apr 17 2012 - 13:56:10 CEST

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