[fluka-discuss]: X-ray spectrum with FLUKA

From: Sokolov, Alexey Dr. <Al.Sokolov_at_gsi.de>
Date: Wed, 17 Jun 2020 11:19:55 +0000

Good day,

I'm trying to estimate the amount of K-shell fluorescence photons from iron target during irradiation with the heavy ion (U-238) beam. The produced amount is lacking few orders of magnitude, if compared with estimations based on (B. Kärcher, J. Quant. Spectr. Rad. Transf. 48, 255 (1992)) . So my question is whether I'm doing something wrong (see the attached input) or the ion impact shell ionization with the subsequent relaxation is not (yet) simulated by FLUKA, as in case of electrons from the thread below?

Kind regards
Alexey


-----Original Message-----
From: owner-fluka-discuss_at_mi.infn.it <owner-fluka-discuss_at_mi.infn.it> On Behalf Of Francesc Salvat-Pujol
Sent: Friday, March 22, 2019 2:15 PM
To: JONAS OLIVEIRA DA SILVA <jonas.silva_at_ufg.br>
Cc: fluka-discuss_at_fluka.org
Subject: Re: [fluka-discuss]: X-ray spectrum with FLUKA

Dear Jonas,

Seems like you essentially want to simulate an x-ray tube. A few
observations:

1) The useful photons are not those that travel further into tungsten (which anyway do not make it very far as you observe), but those that are emitted back into void. It is also customary to make the surface onto which electrons impact form a certain angle away from normal incidence, ~45 deg.

If you adapt your scorings so as to see a bit of the vacuum before your W target, you'll see x-ray emission. To see what happens inside W, adapt the edges and number of bins in your USRBIN, keeping in mind that after say .05 cm electrons are basically out of the game.

2) As you mention, you should eventually obtain a "broad"
Bremmsstrahlung bump and, overlaid, a few characteristic lines. In FLUKA, these lines will arise from the primary electron emitting a Bremsstrahlung photon, this photon having the possibility of ejecting an electron from a target atom (photoionization) and the vacancy being relaxed by the emission of (fluorescence) photons with characteristic energies. However, there is another process contributing to the intensity of the lines at these characteristic energies: the relaxation of a vacancy produced by inner-shell ionization by direct electron impact. The ionization process is modelled in FLUKA, but the subsequent vacancy relaxation not yet. Thus, your simulated characteristic x-ray lines would be lacking intensity.

For this particular application, and considering that fluorescence from vacancy relaxation after inner-shell ionization will most likely dominate the intensity of the characteristic lines, it would make sense to use e.g. PENELOPE code, which does include vacancy relaxation after inner-shell ionization by electron impact.

With kind regards,

Cesc


On Thu, Mar 21 2019, at 11:07 -0300, JONAS OLIVEIRA DA SILVA wrote:
>
>Dear experts,
>
>I'd like to obtain a filtered X-ray tungsten spectra with FLUKA, but
>I've found some problems with the results.
>
>My basic idea is to use a 120 keV electron beam that interacts with a
>cylindrical tungsten target to generate bremsstrahlung and
>characteristic photons. This spectrum will be filtered with a 1.2 mmAl
>aluminum filter, cylindrical shape, that is located at the end of the
>target. I do not know what is going on because it seems that the
>simulated X-ray photons do not reach the aluminum filter.
>
>The .inp file is attached.
>
>Kind regards,
>
>--
>Prof. Dr. Jonas Oliveira da Silva
>Instituto de Física - UFG
>Telefone: (62) 3521 2320



--
Francesc Salvat Pujol
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
Tel: +41 22 76 64011
Fax: +41 22 76 69474

__________________________________________________________________________
You can manage unsubscription from this mailing list at https://www.fluka.org/fluka.php?id=acc_info



__________________________________________________________________________
You can manage unsubscription from this mailing list at https://www.fluka.org/fluka.php?id=acc_info

Received on Wed Jun 17 2020 - 15:10:36 CEST

This archive was generated by hypermail 2.3.0 : Wed Jun 17 2020 - 15:10:58 CEST