Re: Low Residual Nuclei output

From: Paola Sala <>
Date: Fri, 22 Apr 2011 08:47:34 +0200 (CEST)

Dear S. Chatterjee,

Your problem scared us..but fortunately it is a problem of "labelling",
and is solved by changing the what(1) field in the RESNUCLEI card.

This may be relevant to other users, please read the explaination:

Yes, something changed in the last version, and we forgot to document it
in the release notes, sorry.

The change is in the low energy neutron treatment, and has a consequence
on how residual are flagged:

In FLUKA2011, the 4-He and 6-Li from neutron capture on 10-B are
explicitely generated and transported like all secondaries from inelastic
interactions, and become indistinguishable from all other interaction
secondaries..This is independent on the choice made for ion transport.
  As a consequence, when they stop they are scored as residuals from
inelastic interactions, not as residuals from low energy neutrons.

If you change what(1) in the RESNUCLEI card from 2.0 ( low-energy neutron
residuals) to 3.0 ( all residuals) you'll get back all the 4-He you need.

Warning, valid already for fluka2008: the SAME treatment, and "labelling",
applies to protons pronuced in (n,1H) reactions and in (n,14-N) reactions.
If the pointwise treatment is activated, the same applies also to all
products from n reactions on 6-Li.

For your specific case, the new treatment of 10-B may be very useful,
since now you can not only count alphas, but also, if you wish, simulate
their energy deposition and containment in the detectors.

Best regards

> Content-disposition: inline
> Dear Fluka experts,
> I have been using a particular input file since Fluka's last version i.e.,
> Fluka 2008.3d. The residual nuclei output of He-4 was of the order of
> 10^-4. Now after switching over from the 2008.3d version to 2011.2.2
> version, I am finding that suddenly the He-4 production is of the order of
> ~ 10^-9 which is way below the expected values. I have used USRBDX
> detectors also in the input file and their output remains at par with the
> old version. I would like to know whether there is any change with respect
> to residual nuclei calculation in this new version. I have used two
> PHYSICS cards in the input as stated in the manual. As I am scoring only
> the no of He-4 ions, I have switched off the ion transportation. I am
> attaching the input file for your reference.
> I would be thankful for your kind attention in this matter.
> With Regards,
> S. Chatterjee
> Scientific Officer,
> TLD Unit, BARC
> Variable Energy Cyclotron Centre,
> 1/AF, Bidhannagar,Kolkata-64
> Off:+91-33-23184207
> Fax:+91-33-23346871
Received on Fri Apr 22 2011 - 09:43:32 CEST

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