Re: low neutron

Dear Mojdeh,
   I'm sorry if I was not clear... let's make your input file with NEW-DEFA
properly working step by step.

1) the main problem was that if in the defaults the low-energy neutrons are
foreseen (as in NEW-DEFA), FLUKA checks if the low energy cross section tables
are present for every material. If a material has no library (praseodymium in
your case), the program stops. This happens independently on the fact that
later on in the input you swicth off the low energy neutron transport.
This problem can be solved with a trick (as I said: it is not elegant, but it
works). You associate your element to an element whatever in the library: it
is unphysical but you will never use it. You do this via the card LOW-MAT. For
example in your input (you find my modified version in attachment) I
associated your new material to Pb-208 at the temperature of 296 K:
LOW-MAT PRASEODI 82. 208. 296. 208-PB

Then you have to switch off the low energy neutron transport. The two cards:
LOW-NEUT
PART-THR -0.020 NEUTRON NEUTRON 0.0

are enough. In LOW-NEUT what(1)=260 by default and it is correct, please
forgive my imprecision last time! It is absolutely fine and it must not be
changed. LOW-NEUT is here in my opinion redundant (low-energy transport is
already activated by default!) but it is ok. PART-THR with the setting above
switch off the low-energy neutron transport.
As alternative you can use LOW-BIAS with what(1)=1 (you switch off all the
groups) in the region you are interested to do this.

2) About the em thresholds: there are several errors in your input.

    First, Note 3) of the card PART-THR in the manual says:
"Option PART-THR acts on all particles excepted e+ e- and photons, while
EMFCUT option is used to set to transport electrons, positrons and photons".
Then: use only the card EMFCUT, eventually two times (one for the e-,e+ and
photon production (sdum=PROD-CUT) and one for their transport).
Second, the value you have chosen (1 eV!) is under the minimum transport
threshold for em radiation, which is 1 keV. Also 1 keV could be too low... you
have to adapt it to your needs (and please read the manual).

I hope this can help to clarify a bit. I attachment you find my modified
version (I could run it). I did not set explicitly em cuts, but I have chosen
as default PRECISION and I get in this case 100 keV for electrons and 33 keV
for photons (both for production and transport). As I said you can adapt it to
your needs...

Regards,
Anna

Am Sat, 21 Apr 2012 15:09:18 +0430 schrieb mojdeh najm <mm.anjom_at_gmail.com>:
> Dear Ms.Anna
> I set New DEFA with other correction as you told , I tried to decrease the
> threshold for electron and photon. please see that and tell me is that
> right or does it need extra correction?
> In the other hand, I have a question about low-neut card ; you told me
> previous setting was wrong in what(1), that means I should select group 72
> instead of 260, what 's the reason?
> Meanwhile I set Em-cascade without using any extra card in a separate input
> file but I got wrong data.
> I attached both files for each default. I appreciate you for your helpful
> points in advanced.
> Regards
> Mojdeh
>
> On Tue, Apr 17, 2012 at 3:16 AM, Anna Ferrari <a.ferrari_at_hzdr.de> wrote:
>
>> 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,
>> regards,
>>
>> Anna
>>
>>
>>
>> Am Wed, 11 Apr 2012 02:26:01 +0430 schrieb mojdeh najm <mm.anjom_at_gmail.com
>> >:
>> > 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
>>
>>