Re: USRBDX Plot isn't seem Realistic for Scintillator ? need an advice...

From: Paola Sala <>
Date: Thu, 31 Jan 2013 14:50:40 +0100 (CET)

let's start from the easy thing.. yes , the "fraction of deposited energy"
is what you write.

The optical photon spectrum that you get is the scintillation line that
you asked for,550nm wavelength .
You do not see cherenkov and transition radiation because you did not
assign any refraction index to the target material: the OPT-PROP card in
your input has the value of the ref. index, but does NOT have the material
to which it belongs. As a consequence, you had n=1 everywhere- > no
cherenkov, no transition radiation.

Be careful: if you now define correctly the refraction index, you should
also define either an absorption coefficient or some absorbing surface,
otherwise you risk that the optical photons will be confined inside your
target like in a light guide, will not be absorbed, and the simulation
will last forever.

I see also some other details in the input file:
- the optical photons in fluka have nothing to do with "standard" photons,
so it is meaningless to decrease the transport threshold of photons to
cover the visible spectrum. Besides, the cartd for photon threshold is
EMFCUT, not PART-THRES. The transport energy limits for optical photons
are set with OPT-PROP.
Similarly, they do not undergo nuclear interactions, the PHOTONUC card is
irrelevant for your case.

Also, the use of 500 bins in the usrbdx angular distribution seems to me a
bit excessive. Be also careful to one thing: The angle in USRBDX is the
angle between the direction of the particle and the normal to the scoring
surface. In your case, you are using as a surface a tilted box, so the
"angle" will be refereed to different "normals" depending on which face of
the box is the exiting one. If you want to have an angular distribution
with respect to the beam, you should use the USRYIELD card,

Hope this helps

> Hi
> I try to get OPTICAL light output vs. angle when electron beam hits
> scintillator. I get strange results. I get optical photons only on ONE
> energy that corresponds to the green light!
> It shouldn't be so strict, ie. only one line, there should be photons
> with other energies also and peak on that energy.
> Can you take a look if you have time? (what I may miss or did wrong)
> I am little confused about WHAT(2) ("fraction of deposited energy
> going into
> i-th scin. photon emission") parameter of OPT-PROD( sdum SCINT-WV ).
> How can one calculate it?
> I supposed formula Luminosity[ph/ev]*Energy(peak emission)[ev], am I
> right?
> Thanks!
> I am attaching my files
> Cheers

Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148
Received on Fri Feb 01 2013 - 18:21:14 CET

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