Re: [fluka-discuss]: Problem with monoenergetic source

From: Francesco Cerutti <>
Date: Mon, 2 Jul 2018 19:11:31 +0200

Dear Agnieszka,

I'm not sure I understand your expectation. Do you think of the extreme
condition of a fully ionized gas where all electrons got freed and you
are left with a plasma with no chance to produce more charge? I doubt your
real life experiments fit this picture.

Anyway, note that simulations by FLUKA (and other codes) assume that
material properties remain unchanged, so each photon entering your chamber
will see a fully neutral gas.

If I'm not mistaking your setup, your photons have to go through a couple
of meters of air before crossing the chamber walls (Al as well as steel),
so it does not look obvious that the sub-MeV ones should deposit more
energy than the higher energy ones.

Kind regards


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

On Sun, 1 Jul 2018, Agnieszka Witkowska wrote:

> Dear Fluka Experts,
> I am trying to lead in Fluka real life experiment with usage of ionization chamber. I am measuring
> energy deposited in gas of the device. in real life experiment source of radiation was placed 2
> meters from centre of ioniztion chamber. 
> I assume that I do not know how to define correctly beam source to make it similar to real
> conditions. I defined monoenergic, rectangular beam with x and y beam 200cm to make sure that the
> whole device will be surrounded by radiation. 
> I have obtained really strange results. With increasing energy the energy deposited in each
> simulation is increasing as well, what does not match with life experiments, as in some point no
> more electrons should be generated in gas.
> Can You please check my input file and advise what I am doing wrong? Or maybe I am missing some
> physics?
> Below I attached obtained results:
> beam energy [GeV]
> deposited energy
> 0,000059
> 1,79E-08
> 0,000186
> 2,68E-08
> 0,000667
> 5,73E-08
> 0,00117
> 8,85E-08
> 0,005
> 3,07E-07
> 0,01
> 5,11E-07
> 0,02
> 7,19E-07
> Best regards,
> Agnieszka

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Received on Tue Jul 03 2018 - 06:40:53 CEST

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