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
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Received on Fri Mar 22 2019 - 15:24:44 CET