[fluka-discuss]: low energy (E < 1 MeV) heavy-ion transport

From: Robert Bark <bark_at_tlabs.ac.za>
Date: Wed, 3 Feb 2016 16:09:05 +0200

Dear FLUKA experts

I am presently trying to simulate a detector capable of detecting
heavy-ions (190 < A < 240) of low energy ( 0.1 < E < 2) MeV.

The heavy-ions are the recoiling reaction products (thalium isotopes) of
a 62 MeV alpha beam on a thin gold target.
The target thickness is 9e-6 cm. In the simulation, the target is
actually divided into 3 regions, each of 3e-6cm thickness. The target
has to be thin to allow the Tl recoils to escape out of the target and
be detected by a down-stream detector.

It is important to know the energy distribution of the reaction products
to simulate the detector operation.

Here is the problem:

The energy distribution (scored with either USRBDX or USRYIELD) of the
reaction products does not change across the boundaries of the 3 target
layers, nor do any of the reactions products fail to escape the target.
The FLUKA energy distributions agree with what one can calculate
analytically for a fusion evaporation reaction.

This means there is no energy loss of the recoils in the target in the
FLUKA simulation. This contradicts both experiment and SRIM simulations,
where a few 100 keV is expected to be lost.

So far I have used the FLUKA default (PRECISION) and have also tried
adding the cards:

*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8....+....9
IONTRANS HEAVYION
PART-THR -1E-05 HEAVYION HEAVYION 0.0
MULOPT 1. 1. 1. GLOBAL

to no success.

Can anybody advise on the correct input for *low-energy* heavy-ion
transport?

Best Regards
Rob

-- 
Dr Robert Bark
Leader, Radioactive Ion Beam Project
iThemba LABS
www.tlabs.ac.za
tel: 021 843 1123
fax: 021 843 3525
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Received on Wed Feb 03 2016 - 16:36:46 CET

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