Date: Wed, 30 Jan 2013 11:12:07 +0000
Dear Paola, Thankyou for the prompt reply and useful advice, that makes more sense to me now.
The group boundaries controls the bin sizes and this results in fluctuating bin sizes. However when I integrate my double differential yield by multiplying by the bin size to get the neutron current I find the result is very noisy and fluctuates in parallel with the fluctuation in bin sizes. This seems to be a strange result as I wouldn't expect these sort of fluctuations (see attached plot). I can see that I could ignore the fluctuations in bin size and smooth the data but would this be strictly correct?
Kind Regards
Tristan
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-----Original Message-----
From: Paola Sala [mailto:paola.sala_at_mi.infn.it]
Sent: 30 January 2013 08:35
To: Davenne, Tristan (STFC,RAL,TECH)
Cc: fluka-discuss_at_fluka.org
Subject: Re: intervals in usryield card?
Dear Tristan,
when scoring neutrons, the code always respects the energy group structure that is used for low energy neutron transport. In your case, the energy limits chosen in the usyield card correspond to neutron groups from 1 (20 MeV) to 155.
The details are in the manual, in the notes for the USRBDX card:
6) When scoring neutron fluence or current, and the requested energy bin structure overlaps with that of the low energy neutron groups, bin boundaries are forced to coincide with group boundaries and no bin can be smaller than the corresponding group. Actually, the program uses the requested energy limits and number of bins to estimate the desired bin width. The number of bins above the upper limit of the first low-energy neutron group is recalculated according to such width. Note that the lowest energy limit of the last neutron group is 1.E-14 GeV (1.E-5 eV) for the 260 data set.
I would like to add that, if you are interested in neutrons, it is better to include all the energy groups in the scoring, down to the lowest energy.
Regards
Paola
> Hi, I have been trying to score neutrons emerging from a target using
> a double differential yield on a usryield card. On the usryield card I
> specify that I want x1 variable 1 to have 99 intervals in kinetic energy.
> However once I have ran and looked at the result I find that I have
> 155 intervals or some other number that I did not specify in my usryield card.
> Also the intervals are not regular in size. I selected the linear
> option and so I would have thought the intervals should be equal in size!
>
> I attach the input file and would be very grateful for any help on
> this matter.
>
> Many Thanks
>
> Tristan
>
> --
> Scanned by iCritical.
>
>
Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148
-- Scanned by iCritical.
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