From: Francesco Cerutti (Francesco.Cerutti@cern.ch)
Date: Thu Mar 29 2007 - 16:29:05 CEST
Hi Sebastien,
> Then I tried to do it without forcing the energy groups, and my source
> routine looks like Sunil's (uploaded earlier today on the fluka discuss) and
> my results are not good, the spectrum is not properly rendered (see file).
> I used a USRTRACK detector in a 1 cm radius vaccum sphere centered around the
> beam spot (isotropic source point) to score fluence in both cases presented
> in the attached file.
>
> So, has anybody some idea of what is happening ? Results are not identical as
> Alfredo said, what could lead to such a difference ?
the reason is that you plotted (dP/dE)*dE instead of dP/dE (which is what
matters). For the original spectrum it is just a scaling issue
(the energy bins are almost equal, about 200 keV large), but for the FLUKA
spectrum (output bins of different width, given by the groups) you
introduce the distortion shown in the bottom panel.
Following your procedure, I used the source of Sunil (where by the way it
is worthwhile as usual to load the spectrum in double precision - but this
does not affect our problem - ) and I scored by the USRTRACK card. You can
find in attachment the nice matching between the original spectrum and the
FLUKA output (obtained WITHOUT assigning the group number at source level,
as pointed out by Alfredo).
Ciao
Francesco
**************************************************
Francesco Cerutti
CERN-AB
CH-1211 Geneva 23
Switzerland
tel. ++41 22 7678962
fax ++41 22 7668854
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