Re: Solid Angle in USERBDX

Dear Reza,

Please note that (see Manual/USRBDX)

           Angular distributions must be intended as distributions in
           cos(theta), where theta is the angle between the particle
           trajectory and the normal to the boundary at the point of
           crossing.

Thus, theta is not the angle between the beam direction and the particle
trajectory when it crosses the spherical boundary. Could this explain
your observation?

Please also note that USRBDX/What(1)=1 is current scoring and not fluence
scoring as you mention it in your question.

Best regards
Stefan

On Sat, 14 Jun 2008, Reza Taleei wrote:

> Dear Fluka-users,
>
> I would like to calculate Neutron fluence in 30 degree angle. I have
> written the following USRBDX card which calculates neutron fluence from
> PI/6 up to (PI/6)+0.003 but I just get zero fluence. In the same problem I
> can get the desired results by the same card but from 0 up to 0+0.03 solid
> angle. Do I have misunderstandings in the definition of solid angle. AI3
> and AI4 are two spheres. Thank you in advance for your help.
>
> Best regards,
> Reza Taleei.
>
> USRBDX 1.0 NEUTRON -25.0 AI4 AI3 1.0Fne30
> USRBDX 0.03 0.0 100.0.526598775.523598775 1.0&
>
>
>

-- 
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Stefan Roesler
CERN, SC/RP
CH-1211 Geneva 23
Switzerland
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E-mail: Stefan.Roesler@cern.ch