Re: [fluka-discuss]: Absolute efficiency of HPGe detector

From: Andrea Tsinganis <>
Date: Thu, 20 Oct 2016 15:28:53 +0200

Dear Pablo,

Your question is not perfectly clear to me and you also do not mention what
source you are simulating, which might have helped. I am therefore assuming
that you wish to study the absolute efficiency of the detector, understood
as the probability of detection of a γ-ray of a given energy that enters
the crystal, and perhaps compare with experimental data.

Experimentally, you would do this e.g. with a 152Eu source of known
activity at a fixed distance and looking at the known γ-peaks in the
obtained spectrum. You have probably done this already, or will do it soon.
If your goal here is to find the absolute efficiency of your simulated
detector, then you could adopt a similar approach: define an isotropic
source with a known gamma spectrum and then compare it with what is
detected in the crystal.

This can be done at different levels of sophistication, e.g. with
monoenergetic sources at selected energies, or simulating a 152Eu source
(for comparison with an experimental spectrum) or with a source with a flat
energy distribution up to a few MeV. In this last case, your obtained
spectrum would by definition give you the (simulated) detector's efficiency

Note, however, that the absolute value for the efficiency curve at this
stage depends on the distance from the crystal at which you define your
isotropic source (as is the case experimentally), since the angular
acceptance changes. For the absolute efficiency, just direct the gammas so
that they all enter the crystal, or just generate them inside the crystal
to begin with.

Hoping I have answered the right question(s),

On Thu, Oct 20, 2016 at 8:41 AM, Peter Rubovič <>

> Hi Pablo,
> my guess would be to sum the efficiencies for every channel.
> Best regards,
> Peter.
> Dne 20.10.2016 v 3:00 PABLO CESAR ORTIZ RAMIREZ napsal(a):
> Hello fluka users:
>> I have been simulating a HPGe detector and I have been using the Detect
>> card to obtain the energy spectrum. I have noticed that the obtained
>> output file (.lis) give me the response function, i.e. {the number of
>> detected photons by chanel}/{the total number of detected photons}. My
>> question is: how can I obtain the absolute efficiency using this card?
>> or how can I know the number of total detected photons by the detector?
>> Thanks in advance.
>> --
>> Pablo Ortiz Ramírez
>> Master of Science in Physics
>> Faculty of Science, University of Chile
>> Linux User #528950
>> Ubuntu User #32991
> --
> Peter Rubovič
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Received on Thu Oct 20 2016 - 17:18:02 CEST

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