[mcstas-users] Monitor_nD challenge

[Emmanuel FARHI]

Hi,

just read Component manual page 117 "Monitor_nD equivalences". In fact,
the PSD_monitor_4PI is not a 2-angle detector, but an angle-vertical
position (have a look at its code).

Use: options="auto theta bins=90, auto y bins=90, sphere parallel"

The two stripes originate from the poles that are equivalent, and thus the
intensity at 90 degrees (which correspond to a single point on a sphere -
think about the earth), is spread over a -90 +90 vertical angle range.

Emmanuel.


> Hello everybody,
>
> I'm again asking for help on Mcstas, but this time for a component
> behaving strangely. In this test instrument, highly inspired from the
> vanadium example, I have put on parallel two monitors which should give
> the same results: the PSD_monitor_4PI and the Monitor_nD with 4Pi & PSD
> options. And surprise: the monitor_nD always shows two vertical stripes at
> +/- 90°. This doesn't change regardless to the shape or rotation of the
> sample, or the absorption. The people I'm working with here also can't
> explain this strange behavior, so if someone feels concerned...
>
> Thank you in advance
>
> Lionel GERARD
>
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-- 
FARHI Emmanuel <farhi at ill.fr>
Groupe DS/CS, ILL4/156, Tel 04 76 20 71 35
ILL, Grenoble