Re: Normalizatio/Unit of DETECT card

From: Paola Sala <>
Date: Tue, 25 May 2010 11:12:28 +0200 (CEST)

I tried this morning, the EVENTBIN and DETECT card give exactly the same

The normalization of the detect results is very simple, it just counts the
entries in each energy bin. You can compare directly the results of
different codes if you have the same energy bin width. To obtain a
response normalized " per primary photon" , just divide every bin content
by the number of primary photons.

Are you using the same bin width for FLUKA and MCNP?
This might be the problem: the photopeak, being a spike, will always be
contained in one bin only, therefore its height does not depend on the bin
size, while the height of the compton continuum depends on the bin width.

By the way, any meaningful comparison of the spectrum shape with
experimental data must include the smearing due to detector resolution.
Without this, one can only compare the total and photopeak efficiency.

Of course, changing from pencil to isotropic MUST give a large difference,
the detection efficiency is completely different.

> Thanks to your comments. I checked it for pencil beam and various cut
> limits, but the results did not changed anymore.
> However, the MCNP result completely follows the experimental ones (this is
> true for EGS5 also). I think there is a misinterpretation in the results
> of
> the DETECT card, because -as you told- it is different from MCNP's
> pulse-height tally.
> However I found a reasonably good fit between MCNP and "EVENTBIN" score
> for
> EMEnergy. I think this is not an accident. Please verify this case for
> probable inconsistencies.
> Regards
> Ali

Paola Sala
INFN Milano
tel. Milano +39-0250317374
tel. CERN +41-227679148
Received on Wed May 26 2010 - 14:34:26 CEST

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