Re: [fluka-discuss]: Strange pick in gamma energy deposition (antiproton annihilation)

From: <>
Date: Fri, 29 Jan 2021 22:06:56 +0100

Dear Giovanni

there is no such a photon peak, probably there is a misinterpretation in
your mgdraw of the particle id. There is rather an electron peak which is
directly related to the settings of your input where you left the delta
production threshold at the default values of 100 keV which is also the
transport threshold.
So, if you look at electron contributions, you see this peak at 100 kev,
but this occurs just because you set there those thresholds. The energy
loss of charged particles is made up "technically" by two components,
secondary electrons above threshold, and continuous energy losses below
(properly fluctuated). The split between the two is set by the user but of
course physically only the sum makes sense and indeed the sum does not
show any such a peak.

I atach a few files to better explain the point, a plot with the total
energy deposition spectra with your settings, and (second page) the
deposition due to electrons only, and the same plots with the delta and
transport thresholds lowered to 10 keV where the first plot is unchanges,
as it should, while the second one no longer shows the peak at 100 keV. I
also attach the second input and the user routine used to discriminate the
results in the three DETECT estimators (total, electron, phtons, the
latter is always empty as expected)

Hope this helps, sorry for the lengthy explaination


 Dear Fluka expert,
> I am running simulations for a 1 KeV antiproton beam which annihilates on
> a
> carbon target with a 2 micron width. The residuals of the annihilations
> pass through a 0.5 mm silicon detector 1 cm behind the target. I am using
> default PRECISIO, physics EVAPORAT and EMFCUT for photon and electron
> transport (see input file attached).
> I am dumping energy depositions on the detector by every particle entering
> into it with mgdraw subroutine (attached as well).
> As the subject suggests, I am noticing a strange pick in the energy
> deposition of gammas. I attached a screenshot of the distribution for the
> energy deposition of gammas (energy in GeV on the x axis, on y axis the
> number of recurrence of photon depositions in the dump file, I have only
> one step inside the detector for each gamma the number of recurrence is
> equal to the number of photon per energy bin).
> I am puzzled by the pick at 100 KeV. What could be the cause of that pick?
> By comparison with simulations done with geant4 I am wondering if I am
> doing everything correctly because in other simulations I do not even have
> gammas with that energy.
> Thank you in advance for your help.
> Bests regards,
> Giovanni Costantini
> --
> Informativa sulla Privacy:
> <>

You can manage unsubscription from this mailing list at

Received on Fri Jan 29 2021 - 23:49:52 CET

This archive was generated by hypermail 2.3.0 : Fri Jan 29 2021 - 23:50:14 CET