Re: question about set energy group

Dear ZiJia Zhao,

you are binded to the group description of the (260-group) library which
is distributed with the code.

The motivations can be found easily in the Fluka manual (chap.10) where
the low energy neutron transport is described:

[...]
   The multi-group technique, widely used in low-energy neutron transport
   programs, consists in dividing the energy range of interest into a
   given number of intervals ("energy groups"). Elastic and inelastic
reactions
   are simulated not as exclusive processes, but by group-to-group transfer
   probabilities forming a so-called "downscattering matrix".
[...]
   In the library, the first cross section table for an isotope (isotropic
   term P_0) contains the transfer probabilities from each group g to
   any group g': Sum_{g-->g'}/Sum_g, where Sum_g is the sum over all the
   g' (including the "in-scattering" term g' = g). The next cross section
   table provides the P_1 term for the same isotope, the next the P_2
   multigroup cross sections, etc.
[...]
V.

On 11/15/2011 02:13 AM, sszdzl1_at_mail.ustc.edu.cn wrote:
> Dear Fluka experts:
> I am trying to get the spallation neutron spectrum of a lead target, and I want to
> elaborate one especially when the energy under 20 MeV. However, it seems Fluka set the
> energy group automatically under 20 MeV. So is there any way to set the energy
> group by myself? Any help will be appreciated!
>
>
> Best wishes
>

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