[NeXus-committee] Additions to NeXus

[Pete Jemian]

The source is definitely a part of the instrument, not something at the top
level of the experiment (NXentry). Consider the case of a synchrotron X-ray
experiment with a laser pump.  There are two sources to be documented.
They both belong under the description of the pump/probe instrument.

Why should the beam be part of the sample? Makes no sense at all.  The
sample has no beam.  The beam does not describe the sample in any useful
way.  NXbeam documents the state of the beam at some position along the
path from source to detector.  It could go in many places along the optical
path.

Pete
On May 11, 2016 6:17 AM, "Andreas Förster" <andreas.foerster at dectris.com>
wrote:

> Dear NeXus folks,
>
> there was a little discussion last week about possible additions to the
> NeXus standard (and NXmx) to record beam information relevant for the
> estimation of dose.  Herbert proposed a good solution, but the outcome of
> this discussion is still pending.
>
> At DECTRIS, we're keen to tell our customers how to record additional
> metadata in a NeXus-compliant way.  That's why I'd like to have official
> word on the fields below:
>
> Information on the synchrotron should be recorded in an NX_Source group.
> Is /entry/source the right place for that?
>
>      /entry/source *NX_SOURCE*
> <http://download.nexusformat.org/sphinx/classes/base_classes/NXsource.html>
>
> o   *name*: *NX_CHAR*
> <http://download.nexusformat.org/sphinx/nxdl-types.html#nx-char>
>
> §  Name of synchrotron
>
> o   *@short_name*: *NX_CHAR*
> <http://download.nexusformat.org/sphinx/nxdl-types.html#nx-char>
>
> §  short name for source, perhaps the acronym
> Data describing the beam as it hits the sample should probably go the
> NX_Beam group in /entry/sample/beam.  None of the fields below are
> currently defined.  Could these definitions be adopted?
>
> ·      /entry/sample/beam *NX_BEAM*
> <http://download.nexusformat.org/sphinx/classes/base_classes/NXbeam.html>
>
> o   *name*: *NX_CHAR*
> <http://download.nexusformat.org/sphinx/nxdl-types.html#nx-char>
>
> §  Name of beamline
>
> o   *total_flux/xray_flux*: *NX_FLOAT*
> <http://download.nexusformat.org/sphinx/nxdl-types.html#nx-float> {units=
> *NX_RATE* <http://download.nexusformat.org/sphinx/nxdl-types.html#nx-rate>
> }
>
> §  Beam intensity (example: s-1)
>
> o   *incident_beam_size: **NX_FLOAT*
> <http://download.nexusformat.org/sphinx/nxdl-types.html#nx-float>*[2]*
>
> §  Two-dimensional array of FWHM (if Gaussian) or diameters (if top hat)
> of beam
>
> o   *profile*: *NX_CHAR*
> <http://download.nexusformat.org/sphinx/nxdl-types.html#nx-char>
>
> §  Gaussian or top hat
>
> Should the name of the beamline be recorded in beam or in source?  For the
> flux (as a rate - in contrast to the already existing flux density field
> "flux"), either name is fine by me.
>
> I'm happy to discuss these points during the next NeXus meeting.
>
> Thank you and all best
>
>
> Andreas
>
>
>
> --
> <https://www.dectris.com>
> Andreas Förster, Ph.D.
> MX Application Scientist, Scientific Sales
> Phone: +41 56 500 2100 | Direct: +41 56 500 2176 | Email:
> andreas.foerster at dectris.com
> DECTRIS Ltd. | Taefernweg 1 | 5405 Baden-Daettwil | Switzerland |
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