[mcstas-users] divergence monitor output

[Kim Lefmann]

Dear Shu,

Like the other "single-purpose" monitors, the divergence_monitor uses 
Gaussian sigma for the width (in fact, it calculates the standard 
deviation, which is just sigma for a Gaussian).

best, Kim

-----------------
Kim Lefmann
Associate Professor (Lektor)
Niels Bohr Institute
University of Copenhagen

Phone: +45 3532 0476
Mobile:+45 2925 0476

On Mon, 6 Jul 2009, Zhang, SY (Shu Yan) wrote:

> Dear Emmanuel
>
>
>
> Thank you very much for the information. Regarding the divergence output
> dX and dY, are they the full width half maximum or the c value in the
> Gaussian function?
>
>
>
>
>
>
>
> Many thanks for your reply!!
>
>
>
> Shu
>
> -----Original Message-----
> From: Emmanuel FARHI [mailto:farhi at ill.fr]
> Sent: 03 July 2009 20:23
> To: McStas users list at mcstas.org
> Subject: Re: [mcstas-users] divergence monitor output
>
>
>
> 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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>
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>
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>
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>
>>
>
>
>
>
>
> --
>
> FARHI Emmanuel <farhi at ill.fr>
>
> Groupe DS/CS, ILL4/156, Tel 04 76 20 71 35
>
> ILL, Grenoble
>
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>
> -- 
> Scanned by iCritical.
>