Re: Thermal Neutrons Response via PPAC-Detector

From: Alberto Fasso' <fasso_at_SLAC.Stanford.EDU>
Date: Tue, 16 Apr 2013 01:19:44 -0700 (PDT)

Dear Dr. M. Jamil and Kim Hyun Gee,

you said:

> Actually the problem, we have with LIF-converter is; we can?t use it in FLUKA,
> as LIF is compound material.

So what? Define the compound material defining separately 6-Li and F by
means of the MATERIAL command, and then the compound using the command
COMPOUND.
The section of the Fluka Manual you are quoting is completely irrelevant here,
since it refers to pre-mixed compounds that are not available at this time.
Since a pre-mixed compound is not available, use a normally mixed compound as
explained above.

As a default, charged fragments produced by thermal neutrons are not
transported: that is why you "see" them at the gas-gap where they are
produced, but not at the PPAC's gas gap. But for 6-Li it is possible to
make an exception by requesting pointwise cross sections: use LOW-NEUT
command with WHAT(6) = 1. (Leave all other WHATs = 0).
In this way, 3-H and 4-He will be transported and will be detected far
from the production point.

Alberto

> If you have a look at the FLUKA Manual at page 159; (Notes section 4),
> notifies that:
>
>
>
> (Not Implemented!) If WHAT(5) is set > 0.0 because a pre-mixed compound
> low-energy neutron material
>
> is used, average cross sections are used (as for instance in the Morse
> code). Otherwise, if each of the Fluka
>
> elemental components has been associated with one of the elemental
> low-energy neutron components and the
>
> composition of the compound has been dened by a COMPOUND option, low-energy
> neutron interactions will
>
> take place randomly with each individual component, with the appropriate
> probability.
>
>
>
> (1) We used the following mechanism to detect thermal neutrons via 3Li7-
> converter-based PPAC detector.
>
> Neutrons + Li ----------? H3 + He4
>
>
>
> Our problem is we can easily detect secondary particles of the incident
> thermal neutrons at the converter layer.
>
> However if we try to detect at the gas-gap (Isobutane) we can find the
> secondary particles there, why we cant detects them at the PPAC?s gas gap?
>
>
> We will keep waiting for the reply!
>
> Dr. M. Jamil and Kim Hyun Gee
>
> Konkuk University,
>
> EMail: mjamil_at_konkuk.ac.kr
Received on Tue Apr 16 2013 - 11:10:56 CEST