RE: [fluka-discuss]: Low neutrons in Poly, Deuterons and artifact?

From: Francesco Cerutti <>
Date: Tue, 2 Jun 2015 19:42:41 +0200

Dear Georgios,

I'm not sure you fully got the meaning of Luigi's message.
The peaks you reported are not artifacts due to your tiny Al thickness,
rather to the groupwise treatment of low energy (<20MeV) neutrons in
FLUKA, which in your case prevents an event-by-event energy deposition
analysis. When interacting with Carbon nuclei in polyethylene or Neon
nuclei in the gas (or Al nuclei in the foil), your 1 MeV neutrons will
always yield on the spot the respective fixed energy deposition value as
from the kerma approximation, which is normally fine on average but not
suitable for building a Pulse Height Spectrum. Full stop, no specific card
can help.
Still one could count interactions, however irrespective of their outcome.
As written in the manual (LOW-NEUT, note 5), things are different for low
energy neutron interactions on hydrogen (1H).

Concerning the more general problem of minimal thickness, see

Best regards



Dear Luigi,

Thank you very much for your answer.
In my study I am interested in counting efficiencies (total number of
counts in the gas volume).
Since the 50nm thickness of Al foil window produces artifacts, how I could
modify my input using specific cards in order to be able to simulate
What is the minimum thickness of Al that I could consider that FLUKA can
be suitable?
If the Al foil has a thickness of 1-10 microns (instead of 50 nm) do you
think my approach as it is described in my input file might work?

Thank you very much in advance

Best regards


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

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Received on Tue Jun 02 2015 - 21:26:59 CEST

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