Re: simple question + what about semi-conductors detectors ?

From: Sebastien WURTH (
Date: Mon Mar 03 2008 - 16:22:43 CET

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    I have the same question with some solid detector this time, a hyperpur
    Ge cristal for the detection of photons for instance.
    Is it possible to calculate the typical absolute efficiency curve of
    such a detector with FLUKA ?
    I tried several times using several ways and seem to miss something
    there (exemple in *inp file attached).
    I assumed in that case, that all relevant informations are already
    available for FLUKA, since it is the creation of pairs which creates the
    signal... and those interactions are implemented in the standard options
    without adding any options.
    First thing, am I right until there ? Obviously not...
    To calculate some absolute efficiency, I used the DETECT card in FLUKA,
    with one region which consists in my Ge detector.
    I make as many runs as various energies from 50 keV to 2 MeV for instance.
    I expect to obtain a curve which shows a maximum value of efficiency at
    ~100-120 keV (see first plot in attached *.pdf file).
    I don't get that, I only get a curve that looks like "stopping power",
    the more "counts" with the lowest energies, and a decrease when the
    values of energy gets higher (see second plot in attached *.pdf file).
    So, maybe it is normal, it is what DETECT card calculates (energy
    deposition), but is it possible also to simulate the efficiency of the
    photons detection ?
    I tried with other detectors like USRBIN or USRTRACK, but this is not
    what I want. I want some ratio between what is detected and what is
    emitted (at a given energy). Is there still some physical effect to
    introduce in order to achieve this (like for scintillation effects) ie
    the third thing pointed out by Alberto in his answer to Sandra (see below) ?

    Any comment or hint would be highly appreciated.


    (For pretty girls I don't know, but for bringing some food, no problem :))

    Alberto Fasso' wrote :

    >Dear Sandra,
    >the detection efficiency is the results of several different things.
    >Some of them FLUKA can calculate, but some information must be provided
    >by you:
    >1) Geometrical acceptance of the detector: FLUKA does it
    >2) Energy deposited in the detector: FLUKA does it
    >3) Response of the detector for that deposited energy: needs some input
    > from you.
    >For point 3) there are two possibilities:
    >a) to provide one or two Birks quenching coefficients (see the manual
    > about command TCQUENCH). For some scintillators, these coefficients have
    > been measured and published, see for instance the reference mentioned
    > in the example of the manual following the description of the command.
    > This choice only gives you the fraction of deposited energy which is
    > converted to scintillation photons, but not the self-absorption of those
    > photons inside the detector, nor the fraction of photons reaching the
    > photocathode and being detected by it.
    >b) to simulate explicitely the production of scintillation photons (see
    > command OPT-PROD, with SDUM = SCINTILL or SCINT-WV or SCINT-OM), and their
    > transport (command OPT-PROP).
    > You must provide up to 3 photon monochromatic energies, together with the
    > respective fraction of deposited energy going into each of the 3 lines.
    > You must also provide the optical properties of the scintillator (energy
    > or wavelength range for the transport, refraction and absorption index)
    > and the quantum efficiency, or sensitivity of the the photocathode.
    >As the latin poet Catullus said:
    >Coenabis bene, mi Fabulle, apud me
    >si tecum attuleris bonam atque magnam
    >coenam, non sine candida puella...
    >(You will dine well at my table, dear Fabullus,
    >if you will bring with you a good and big dinner,
    >and possibly also a nice girl...)
    >On Wed, 27 Feb 2008, Sandra Moretto wrote:
    >>Dear fluka-users,
    >> my situation is very simple.
    >>I have an isotropic source of neutrons with E<20 MeV.
    >>and a Cylindric Scintillator placed at 50 cm away from the source.
    >>I'd like to calculate the detection efficiency.
    >>It is feasible to use fluka for that?
    >>Thanks for the attention
    >> Sandra
    >>Dipartimento di Fisica
    >>Via Marzolo 8 - 35131
    >>Padova (ITALY)
    >>Tel: + 39 049-827 7181

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