Re: use of CERNLIB with Fluka (source)

From: Alberto Fasso' <fasso@SLAC.Stanford.EDU>
Date: Thu Mar 27 2008 - 20:05:42 CET

Dear Noemi,

I discussed it with Francesco, and it is not clear to us which kind of
isotropic source you intend to implement, since you are reading your cosines
from an external file. The solution suggested by him (reproduced below) and
by Sebastien (using the RACO routine) apply only to an isotropic point source.
But if you are trying to describe a uniform isotropic flux inside a certain
volume (as I suspect since you are dealing with cosmic rays) the correct
routine to use is SFLOOD:


* This is a subroutine of FLUKA9x/200x for sampling a random *
* position and direction on a unit radius sphere, such that to *
* generate a uniform and isotropic fluence inside *

Note that SFLOOD generates a random position on a sphere of radius 1, so you
will have to normalize it to the actual radius of the sphere where you want
a uniform isotropic field.

A discussion on SFLOOD can be found on the archive of this list, see
and the 4 following mails


On Thu, 27 Mar 2008, Francesco Cerutti wrote:

> But you can implement an isotropic sampling directly in your source routine,
> according to the Sebastien's suggestion or, e.g., sampling uniformly between
> ZERZER and TWOPIP the azimuthal angle and between -ONEONE and ONEONE the
> cosine of the polar angle.

Alberto Fasso`
SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025
Phone: (1 650) 926 4762   Fax: (1 650) 926 3569
Received on Fri Mar 28 00:06:02 2008

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