Re: [fluka-discuss]: Neutrons

From: Francesco Cerutti <>
Date: Thu, 22 Oct 2015 21:07:40 +0200


First of all, the reaction of your interest - as any other *low energy
neutron* reaction, apart from few exceptions documented in the manual - is
not simulated *explicitly* in FLUKA. So, out of your USRYIELD scoring, you
will never see alpha particles produced by neutrons in Be.
You can find instead (uncorrelated) nuclear residues (like 4He and 6He) by

Conversely, in principle you can get neutron production in lead from your
electron beam, provided that your photon generation (that can be biased by
EMF-BIAS with SDUM=LAMBBREM) and photon nuclear interaction length biasing
(LAM-BIAS, in lead) is enough. And you can score the neutron spectrum for
instance by USRTRACK.

Concerning your input:

- I would lower the electron/photon transport threshold down to 5
MeV (instead of 10 MeV), below the photonuclear threshold in lead (with
EMFCUT). No need for a specific EMFCUT/ELPO-THR card.

- your LOW-MAT makes no sense (you assign to the predefined LEAD material
... no set of low energy neutron cross sections; anyway the ones of
natural lead at 296K are taken)

- LOW-NEUT is useless (with DEFAULTS/PRECISIO, neutrons are transported
down to thermal energies)

- I do not see the point for RADDECAY, which is intended to ask for
radionuclide decay.

- In your region definitions, there is no point in repeating more than one
time +void (or +target) inside the same zone.

- RESNUCLE in the VOID region (VACUUM) makes no sense.

- Back to your useless USRYIELD mentioned at the beginning, remember for
general use that WHAT(12) (translated by Flair as "Kind") must be 3.0
(double diff. yield) and not 1.0 (double diff. cross section, obtained by
multiplying the aforementioned yield by the reaction cross section - in
hydrogen, if not differently specified in the same USRYIELD - of the beam,
i.e. 22 MeV electrons in your case!).

Kind regards

Francesco Cerutti

CH-1211 Geneva 23
tel. ++41 22 7678962
fax ++41 22 7668854

On Wed, 21 Oct 2015, kabytayeva wrote:

> Hello everyone!
> Dear,FLUKA experts!
> At the moment I am studying production of helium-6 in the reaction 9χΕ(n,4He)
> 6ξΕ, ie, electrons with energy 22MeV are bombarded the converter, which is
> made of lead. As a result neutrons are interacted with the Be target, which
> is diameter 10cm. And I have the following questions:
> 1) Please, check my input file, because I am working with FLUKA recently,
> especially the reaction threshold
> 2) Can I obtain energies of the neutrons with which they are emitted from
> the lead via FLUKA?
> Thank you so much!!!

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Received on Thu Oct 22 2015 - 22:24:30 CEST

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