From: Alberto Fasso' (fasso@SLAC.Stanford.EDU)
Date: Fri Jan 18 2008 - 23:29:22 CET
I fully agree with the advice given by Francesco.
Let me just add a little trick: it is true that you cannot increase
the transport threshold in vacuum, but it is possible to "cheat" the
program by making a very thin region (e.g 0.001 cm thick) full of a very
low density gas (hydrogen has the lowest density of all FLUKA
pre-defined materials). Although the probability of electrons interacting
in that region is negligible, that region is not "vacuum": therefore
you can set there a very high transport threshold.
Alberto
On Fri, 18 Jan 2008, Francesco Cerutti wrote:
>
> Dear Jeff,
>
> you might benefit from biasing.
>
> To increase the efficiency of bremsstrahlung photon production, you can
> reduce the interaction mean free path for electron bremsstrahlung in your
> target (EMF-BIAS card with SDUM = LAMBBREM).
> Moreover, to get rid of electrons escaping the target, you can assign lower
> importance to regions downstream from the target, for electrons only. In
> order to do this, you need to include few BIASING cards. With WHAT(1)=2.0 and
> WHAT(2)=0.0 you can set a reduced importance for the mentioned regions
> (regions not indicated will have a default importance equal to 1.0). With
> WHAT(1)<0.0 and WHAT(2)=0.0 you can switch off importance biasing for
> particles other than electrons. Please refer to the manual for more biasing
> details.
> As you pointed out, increasing the transport threshold in vacuum regions is
> not effective, since there electrons cannot stop and deposit their energy.
>
> Hope this helps
>
> Best regards
>
> Francesco
>
> **************************************************
> Francesco Cerutti
> CERN-AB
> CH-1211 Geneva 23
> Switzerland
> tel. ++41 22 7678962
> fax ++41 22 7668854
>
>
-- Alberto Fasso` SLAC-RP, MS 48, 2575 Sand Hill Road, Menlo Park CA 94025 Phone: (1 650) 926 4762 Fax: (1 650) 926 3569 fasso@slac.stanford.edu
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