From: Alfredo Ferrari (alfredo.ferrari@cern.ch)
Date: Thu Nov 07 2002 - 12:45:33 CET
Dear Ludwik
there is no gamma production available in the evaluated nuclear data files
for Gadolinium isotopes. If you look in the (FLUKA) manual, it is
explained even though in a way (too much) terse:
"A symbol Y or N in column "RN" refers to availability of information
about production of residual nuclei; in column "Gam" to information
about gamma production"
The neutron cross sections below 20 MeV are generated out of standard
evaluated nuclear data files (ENDF, JEFF, JENDL etc). To my knowledge
no one includes the data for gamma production out of gadolinium. Indeed
they often do not include data about gamma production (they are of
relatively scarce interest for reactor applications), gadolinium is not
a rare case. If the photon production data are not there the Q energy goes
into the kerma and full stop. Of course this is bad if one wants to follow
the gammas as often it is the case. This is a problem with the evaluated
nuclear data files which cannot be easily circumvented, unless one is
willing to do his evaluation of (at least capture) photon production
for a given isotope and add it to FLUKA or whichever else code (the
problem is there for all codes using the evaluated nuclear data files
below 20 MeV of course, like MCNP etc).
We did this in the past for Cd, Argon and Xenon and it is a bit of a
nightmare. I'll try to find the note describing the work done for the Xe
isotopes just to let you know the kind of problems. If for you it is
critical and you are brave enough to do this task, we can help and
implement the result.
I hope the answer is clear even though surely it is
not of much help!
Ciao
Alfredo
On Thu, 7 Nov 2002, Ludwik Pienkowski wrote:
> Dear FLUKA authors and users,
>
> I'm tracking the slow (Ekin<5MeV) neutrons inside a large
> detector which is filled with 1.5m3 of liquid scintillator.
> The FLUKA calculation were done with cards:
> DEFAULTS, SDUM=PRECISIO
> PHYSICS , SDUM=EVAPORAT, what(1)=2.0
> The *.pemf files were prepared using the FLUKA version from
> May-2002.
>
> The first test run was performed with a scintillator NE343,
> based on C9H12. The "USer dependent DRAWing" entry (inside
> the mgdraw routine) shows the interaction history. The neutron
> is captured inside the detector (in most of the cases) and the
> gamma with energy 2.22MeV is emitted.
> The next test calculation was done with the modified NE343.
> The scintillator was loaded with Gadolinium (0.4% by weight).
> The neutrons are now captured faster than during the first test,
> and they are captured mostly by the Gadolinium. However, the "USer
> dependent DRAWing" entry doesn't show any gamma emission
> from the Gadolinium. The last record for each event shows the
> information that neutron was captured and the excitation energy
> (include (FINUC), common /finuc/, variable tv) is 8.015 MeV.
> My question is: where are the gammas emitted by the excited
> Gadolinium?
>
> Best regards
> Ludwik Pienkowski
>
>
-- +----------------------------------------------------------------------------+ | Alfredo Ferrari || Tel.: +41.22.767.6119 | | CERN-SL || Fax.: +41.22.767.7555 | | 1211 Geneva 23 || e-mail: Alfredo.Ferrari@cern.ch | | Switzerland || Alfredo.Ferrari@mi.infn.it | +----------------------------------------------------------------------------+
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