Re: Inelastic interactions below 20 MeV

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Thu, 10 Mar 2011 08:04:34 -0800 (PST)

Dear Sunil,

as you can see in a prevous mail by Paola Sala:
http://www.fluka.org/web_archive/earchive/new-fluka-discuss/3510.html
"In the transport of low energy ( below 20 MeV) neutrons, there is no
distinction between elastic and inelastic scattering".

Multigroup neutron transport is based on a "downscattering matrix".
An interaction point is sampled based on the total neutron cross section,
and the matrix is used to sample the new energy group where the neutron
will be next. You cannot know where the interaction was a scattering
(elastic or inelastic) or an (n,2n) reaction etc. You know only that
the neutron has changed energy and direction.

Alberto

On Tue, 8 Mar 2011, Sunil C wrote:

> Hi All
>
> Let me also add:
>
> It is just not that neutrons are not emerging from the inelastic
> interactions, but none are entering into an inelastic interaction either,
> below 19.6 MeV.
>
>
> Regards
>
> Sunil
> ..............
>
> On Tue, Mar 8, 2011 at 2:28 PM, Sunil C<csunil11_at_gmail.com> wrote:
>
>> Hi All
>>
>> I have been trying to score some neutrons emerging from inelastic
>> interactions using the USRYILED option by setting WHAT(4) = -1 and
>> WHAT(5)-2.
>> with lead as the target material and neutrons as the primary particle.
>>
>> While I can see results above 20 MeV incident energy, it falls to 0.0 right
>> below that.
>>
>> Since there should be some interactions happening below about 15 MeV in the
>> case of Pb and many other materials;
>>
>> 1. Are such interactions invoked at all below 20 MeV (19.6 MeV to be
>> precise) due to the group structure?
>>
>> 2. Or is it just a matter of scoring through some other technique?
>>
>> Thanks a lot
>>
>> Sunil
>>
>
>
>

-- 
Alberto Fasso`
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
fasso_at_slac.stanford.edu
Received on Fri Mar 11 2011 - 15:56:47 CET

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