[mcstas-users] divergence monitor output

[Emmanuel FARHI]

Hello Shu,

Any divergence monitor such as the Divergence_monitor() or the
Monitor_nD(options="hdiv vdiv, all auto") will indeed produce a divergence
map.

Then the output files have lines:
  value: I I_err N
  statistics: X0 dX Y0 dY
where
I, I_err and N: are the values of the intensity (usually integrated flux),
the error bar on this value, and the number of statistical MC events
recorded on the detector (which is not the flux, but a non physical event
count, only for computational purpose).

X0 dX Y0 dY: are the center (mean value, 1st moment) and second moment
(gaussian width) of the distributions. In your case, dX and dY will give
you a gaussian width of the H and V divergence. X0 and Y0 should in
principle be around zero if the monitor is well oriented.
just do
>> eval(mc_divmon_dat.statistics); [ dX dY ]


Emmanuel.

> Dear all
>
> I have question about the results from the Divergence_monitor Component.
> I want to find out the beam divergence. Is this the right monitor to
> use? If it is, which value in the output file shall I use as the maximum
> divergence? What do these values X0, dX, Y0 and dY from
> "mc_divmon_dat.statistics" mean? What are the meaning for the values
> from "mc_divmon_dat.values"?
>
> Best regards,
> Shu
>
>
>
> --
> Scanned by iCritical.
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-- 
FARHI Emmanuel <farhi at ill.fr>
Groupe DS/CS, ILL4/156, Tel 04 76 20 71 35
ILL, Grenoble