Re: [fluka-discuss]: coincidence scoring

From: <me_at_marychin.org>
Date: Tue, 20 May 2014 22:51:13 -0700 (PDT)

Dear Philippe,

Assuming I understood your question well, the DETECT card can do the job. The
trigger is triggered by energy deposition, in the trigger region(s), by *any
particle belonging to the same parent source* (re: footnote), regardless of
whether trigger signal occurs before or after energy deposition in the detector
region(s).

As a test to convince ourselves we can send a photon through two successive
regions. To ensure no backscatter we can have a dense material for the first
region, and set regional transport cutoffs in the second region to a value
exceeding the beam energy. In the DETECT card if we then set the first region as
the detector, and the second region as the trigger, energy will be deposited in
the detector first, signal will be triggered in the trigger region later. We'll
find that DETECT happily recognises the energy deposition in the detector. The
numbers reported by DETECT output (fort.17) can be verified against the energy
deposition table in .out (can be located by text-searching for 'Feeder', or
'Events by Region' under fless).

We can also test the corollary: swapping the detector region and the trigger
region would still produce DETECT output which is consistent with .out.

As you mentioned we can of course use user routines. Note though the different
interpretations of before-after: before-after in terms of wall-clock and also in
terms of upstream-downstream of a radiation cascade; before-after in terms of
FLUKA tracking which particle first and which particle emerges from the stack
first (which is entirely programmatic, absolutely unphysical). With user
routines we would need to set a trigger flag, whose lifetime and validity need
to be considered in terms of the order FLUKA tracks progenies and the order
progenies get pushed and popped out of the stack. Propagation of flags through
progenies should be done via ISPUSR, otherwise as far as I can imagine the mess
would be unsurmountable.

Footnote: *Any particle belonging to the same parent source* is defined in the
DETECT section of FLUKA's manual as:
"primary particle and its descendants, i.e. between two successive calls to the
FEEDER subroutine (case of an incident beam) or to a user-written SOURCE
<http://www.fluka.org/fluka.php?id=man_onl&sub=71> subroutine (case of an
extended source, or of a source read from a collision file or sampled from a
distribution)"
In the nomenclature of fellow Monte Carlo house-brands, this is commonly
referred to as, "progenies belonging to the same history".

:) mary

> On 19 May 2014 at 09:05 Philippe Velten <Philippe.Velten_at_fys.kuleuven.be>
> wrote:
>
>
> Dear FLUKA experts,
>
> I would need some advanced coincidence scoring capabilities to simulate a
> beta-gamma spectroscopy setup.
> More precisely, I would like to score energy deposition in one detector (beta
> signal in the beta detector) at the condition that a delayed gamma ray is
> detected in an other detector (e.g. a energy deposition with a 2 sided energy
> selection).
> I don't think this kind of feature is possible with the available DETECT card
> and its coincidence capabilities but please correct me if I am wrong.
> It seems that currently the designated "trigger" must arrive BEFORE the
> "detector" signal. In my case, I could switch my trigger and signal, e.g.
> consider that the beta signal is the trigger and the gamma signal is the
> detector and this way I would get a coincidence count, but then no beta
> spectrum...
>
> I guess I could use the mgdraw routines to build a custom scoring from scratch
> but I would like to use built-in scoring and data processing capabilities of
> FLUKA as much as possible.
> So please could you tell me if there is a way to implement such coincidence
> capabilities with minimal addition?
>
> A possibility would be a routine called at the end of each event (usreou.f for
> example) but with access to the energy deposited in the volumes designated as
> "detector" and "trigger" with the DETECT card and with the possibility to
> assign null weight to some of those scoring under some conditions.
> In my case, give a null weight to the energy deposition in the beta detector
> if the energy deposited in the gamma detector doesn't corresponds to the the
> gamma ray energy.
>
> Best regards,
> Philippe
>
>
Received on Wed May 21 2014 - 09:07:00 CEST

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