Re: [fluka-discuss]: Light output of Inorganic scintillator

From: Anna Ferrari <>
Date: Sun, 03 Nov 2013 13:59:21 +0100

Dear Xiaokun Zhao,

as you already saw by yourself, you can use FLUKA to describe the response of
your scintillator, but remember (you already realized it) that you have always
to give in input somehow the characterization of your detector.
I suggest you to read this very interesting post of Alberto Fasso' on the

Maybe it is useful to repeat here the main points.
You can describe the scintillator response in different ways, not only by
using optical photons.

The most important information that FLUKA gives you, together with the
possibility to evaluate the acceptance of your detector, is the energy
deposition in the scintillating material.
 From this point on you can proceed in different ways:

1) as you mentioned, you can correct the values of the deposited energy to
take into account the Birks effect, which is the saturation of the light
output due to the quenching interactions between the excited molecules along
the path of
incident particles.
You can provide the Birks parameters in two ways:
- in the USERDUMP card with sdum=UDQUENCH, if you want to intercept the
tracking. In this case you can retrieve the quenched values of the deposited
energy via the user routine MGDRAW (see also this post:
for more details);
- via the TCQUENCH card if you score the quenched deposited energy via USRBIN
In order to compare with the experimental signals the FLUKA results in terms
of deposited energy, you have still to transform these results by folding the
photon attenuation in the scintillator, the quantum efficiency of your
phototubes, the different effects of the discriminator thresholds in your
electronics, and so on....
You have to write your own routines to do that.

I think that this is what we normally need for many applications.

2) as you already experienced, a second way is to implement the generation of
optical photons. This is a very nice and useful step forward in the radiation
transport, but remember that here you have to input all the parameters that
characterize the scintillator with respect to the light generation (via
OPT-PROD) and the optical properties for the photon transport (via OPT-PROP).
In particular for the production you must provide:
a) the energy (or the energies, you can provide up to 3) of the emitted
scintillating photons;
b) the fraction of the deposited energy going in scintillation photons (for
each photon energy if you have more then one).
Because you are tuning directly by input card the lattest quantity, the Birks
effect here is not anymore taken into account (it is implicitly considered in
the experimental input b) that we have to provide).
How to calculate b)? If you know the energy(/ies)of the emitted scintillating
photons (let's suppose we have only one, E_sciph) AND the measured light
output as number N_ph of photons per MeV of deposited energy in the
scintillator, you can calculate this fraction simply as:
E_sciph[MeV] x N_ph/MeV

 From this point on you proceed as in the previous case: you have to fold
 offline the scintillator light output with all the effects (the phototube
response and so on...).

Hope it helps,
kind regards

Am Mon, 28 Oct 2013 19:07:47 +0800 (CST) schrieb <>:
> Dear FLUKA experts,
> Hello
> I use neutron beam to hit the plastic scintillator and want to get the
>light output from the other side.
> At first,I want to use the birks formula. But the birks formula can only
>convert the energy deposition to the optical photons and
> does not include the transport process.So I can not get the information from
>the output end of the plastic scintillator.
> Now I want to use fluka to simulaton the whole process,include the
>generating and propagating secondary particles, and the opticla photons
> can be received by photomultiplier at the output end.
> Can I do it use fluka?
> Must I wirte the user routines? And which user routines should I use?
> Thanks for your help!
> Xiaokun Zhao

Dr. Anna Ferrari
Institute of Radiation Physics
Helmholtz-Zentrum Dresden-Rossendorf e.V.
Bautzner Landstra├če 400
D - 01328 Dresden (Germany)
Tel. +49 351 260 2872
Received on Sun Nov 03 2013 - 14:49:12 CET

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