Re: [fluka-discuss]: scoring heavy ions of nuclear reaction, how to obtain the ion fluence?

From: Francesc Salvat-Pujol <>
Date: Wed, 6 Jun 2018 11:12:11 +0200

Dear Yang,

Note that the feature you implicitly request (production and transport
of alpha and Li from B under n bombardment) needs pointwise cross
sections for low-energy neutrons. Furthermore, in the case of B it
should be kept in mind that pointwise cross sections are available in
FLUKA for the reaction 10B(n,alpha)7Li only.

The next point to keep in mind is that the correspondence between FLUKA
material and low-energy neutron cross section material is done on a
material-name basis (often requiring some extra identifiers in the

The way you had B in your input file (named BORON), FLUKA was picking
up the low-energy neutron cross section for natural B, the first
instance of BORON in the table you can find in the manual under} List of materials for which cross sections are available in the
            260 neutron, 42 gamma group library:

... for which there are no available pointwise cross sections in FLUKA.

If you name your boron BORON-10, FLUKA will provide the indeed available
low-energy neutron cross sections for 10B at 296 K, which you can check
is the first instance of BORON-10 in the table above.

For the particular reaction 10B(n,alpha)7Li, pointwise cross sections
are automatically activated. Thus, for this particular case there is no
need to pass an additional LOW-NEUT card to request pointwise low-energy
neutron cross sections.

As a result of renaming your boron to BORON-10, and of the fact that
pointwise cross sections are automatically active for 10B(n,alpha)7Li,
your alphas will be generated and transported, and idem for your 7Li
(transported, unless I'm mistaken, thanks to the IONTRANS card you

Hoping this was reasonably accurate and helpful,


PS: A few minor coments after a quick look at your input file: I see you
explicitly pass an EMF card. Note that since you are using DEFAULTS with
PRECISIOn, EMF is already activated anyway (see the manual).

PS2: you pass relatively low delta-ray production thresholds (1 keV).
Adapt the FUDGEM parameter (fraction of atomic electrons contributing to
multiple Coulomb scattering, i.e. WHAT(3) in the EMFCUT card with
SDUM=PROD-CUT) accordingly, giving it a relatively low value, say 1e-5.

On Mon, Jun 04 2018, at 15:07 +0800, YANG Tao wrote:
>Dear FLUKA users,
> Recently I am research the energy spectrum of B(n,α)Li reaction, I use USRBDX card to score the energy spectrum of α and Li, but unfortunately I get nothing. I have switch on ion transportation(IONTRANS card). Maybe just I don't know how to set the relevant card, such as PHYSICS and IONTRANS card. Could anyone help me to point out the mistakes? Attachment is the input file. Any suggestion is appreciated!
>Best regards!

Francesc Salvat Pujol
CH-1211 Geneva 23
Tel: +41 22 76 64011
Fax: +41 22 76 69474
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Received on Wed Jun 06 2018 - 12:28:07 CEST

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