calculating the number of (n,2n) reactions

I would like to clarify some points about what Anna said.

1) Reactions such as (n,2n) cannot be identified when the incident
    neutron has an energy < 20 MeV. The low-energy neutron cross sections
    used by FLUKA are "inclusive", meaning that all neutron producing
    channels (n,n'), (n,np), (n,alpha), (n,2n) are merged into a single
    channel, with one single neutron emitted as secondary, having an energy
    sampled from the combination of all above reactions, and a weight
    corresponding to the actual neutron multiplicity
2) On the other hand, for neutrons with energy > 20 MeV, as well as for
    all other particles (gamma, protons, etc.) the number and characteristi=
cs
    of the secondaries can be obtained in the USDRAW entry of MGDRAW, looki=
ng
    for ICODE =3D 101 (=3D inelastic interaction) and inspecting the conten=
t
    of COMMON GENSTK (generator stack). NP is the number of secondaries
    after the inelastic interaction, and the user can check the characteris=
tics
    (particle type, energy, direction, weight) of each of the NP particles.
    Look at file (GENSTK) in $FLUPRO/flukapro for the names of the variable=
s.
3) The STUPRF and STUPRE user routines allow the user to store some
    properties of the secondaries in special variables, so that they can
    be inherited by the particles of the next generation. But they cannot
    be used to "get informations about the occurred interaction and the
    secondaries". For this purpose, see the point 2) above.

Alberto

On Tue, 18 Nov 2008, Anna.Ferrari_at_lnf.infn.it wrote:

> Hi Andrzej,
>
> if you want for example to study a given reaction in a particular region
> of interest, I would suggest you to do an event analysis by using:
> - the MGDRAW user routine (activated by the USERDUMP card) for
> the general analysis of each transport particle;
> - the STUPRF and STUPRE user routines, where (in the cases of
> hadrons/muons and electrons/photons respectively) you can get
> informations about the occurred interaction and the secondaries, that
> have been produced.
>
> If for example you want to count the interactions of interest in the who=
le
> target, you can work in the USDRAW subroutine (in mgdraw.f);
> if you are interested only at the secondaries that come out from your
> target, you can work in the BXDRAW (boundary crossing drawing) subroutin=
e
> (always in mgdraw.f).
>
> In this second case, if you are also interested to the calculation of
> the total interaction rate (i.e. the total cross section, without
> selecting a particular reaction) I would suggest also to consider the
> USRYIELD card, that - with an appropriate setting of what(6) - allows
> the calculation of the plain double differential cross-section or the
> invariant cross-section (the warning is: the calculation has a little
> meaning in the case of thick target)
>
> Hope it helps,
>
> cheers,
>
> Anna
>
>
>
>
>> Dear FLUKA users,
>> I have a simple question. How can I calculate total number of given sort
>> of
>> reaction (for instance (gamma,n) or (n,2n))?
>>
>> Andrzej Wojciechowski
>>
>
>

--=20
Alberto Fass=F2
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
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Received on Wed Nov 19 2008 - 10:20:28 CET