Re: [fluka-discuss]: volume of scoring region

From: Francesco Cerutti <>
Date: Tue, 16 Dec 2014 23:37:00 +0100

Dear Hamideh,

you seem to believe that the division by volume is introducing an
arbitrary normalization scaling your results. This is a fundamental
misconception. Dose equivalent, which is weighted fluence (i.e.
tracklength *divided by volume*), is an intensive quantity, which does not
scale with volume, since it embeds in its definition the division by
volume. If you think of an uniform field, where fluence and dose
equivalent are constant, you realize that you get as expected the same
number irrespectively of the scoring volume, provided that you divide the
tracklength calculated on it (proportional to the volume) by the volume.
Now, the fact that your results do depend on the scoring volume, over
which they are averaged, is just because you have - as usual - a not
uniform field. In order to compare to an analytical value at a given
angle, ideally one would need a ... zero volume, i.e. an infinite
resolution, which is not possible and is not real. More practically, one
would need to choose a volume where the dose-eq/fluence variation is
minimal, still paying attention to the fact that small bins, while giving
in theory better resolution, imply small statistics, i.e. larger
statistical errors, calling for an adequate number of primaries.

Best regards


Francesco Cerutti
CH-1211 Geneva 23
tel. ++41 22 7678962
fax ++41 22 7668854

On Tue, 16 Dec 2014, Hamideh Jalali wrote:

> Dear Fluka experts
> In my problem a 3 GeV electron beam strikes a lead target. I would like to
> score dose equivalent from photons and neutrons behind concrete shield in
> forward and lateral directions and compare the results with analytical ones.
> I used USRBIN for my purpose. Since the results are normalized by volume in
> Cartesian binning, I got different values for dose equivalent with different
> sizes of scoring region in USRBIN detector.
> How I can find the correct volume of the scoring region such that the
> simulation results are comparable with analytical ones in 0 and 90 degrees.
> Best Regards
> Hamideh   

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Received on Wed Dec 17 2014 - 00:57:20 CET

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