[NeXus-committee] Additions to NeXus

Wed May 11 13:14:20 BST 2016

Dear Pete,

thanks for clarifying the points about the source.

Regarding the beam, I hope you are kidding.  We're in the middle of
switching incident_wavelength from /entry/instrument/beam to
/entry/sample/beam to conform to the NXmx definition where beam is part of
the sample.  If that turns out incorrect, our software developers will get
a fit.

*(sample)*: *NXsample*
<http://download.nexusformat.org/sphinx/classes/base_classes/NXsample.html#nxsample>

*name*: *NX_CHAR*
<http://download.nexusformat.org/sphinx/nxdl-types.html#nx-char>

Descriptive name of sample

*depends_on*: *NX_CHAR*
<http://download.nexusformat.org/sphinx/nxdl-types.html#nx-char>

This should be an absolute requirement to have for any scan experiment. The
reason it is optional is mainly to accommodate XFEL single shot exposures.

*temperature*: *NX_CHAR*
<http://download.nexusformat.org/sphinx/nxdl-types.html#nx-char> {units=
*NX_TEMPERATURE*
<http://download.nexusformat.org/sphinx/nxdl-types.html#nx-temperature>}

*(beam)*: *NXbeam*
<http://download.nexusformat.org/sphinx/classes/base_classes/NXbeam.html#nxbeam>

*incident_wavelength*: *NX_NUMBER*
<http://download.nexusformat.org/sphinx/nxdl-types.html#nx-number> {units=
*NX_WAVELENGTH*
<http://download.nexusformat.org/sphinx/nxdl-types.html#nx-wavelength>}

*flux*: *NX_FLOAT*
<http://download.nexusformat.org/sphinx/nxdl-types.html#nx-float> {units=
*NX_FLUX* <http://download.nexusformat.org/sphinx/nxdl-types.html#nx-flux>}

flux incident on beam plane area

*incident_polarisation_stokes[np, 4]*: *NX_CHAR*
<http://download.nexusformat.org/sphinx/nxdl-types.html#nx-char>

*incident_wavelength_spectrum*: *NXdata*
<http://download.nexusformat.org/sphinx/classes/base_classes/NXdata.html#nxdata>

*(transformations)*: *NXtransformations*
<http://download.nexusformat.org/sphinx/classes/base_classes/NXtransformations.html#nxtransformations>

Suggested location for sample goniometer or other axes (transformations)

All best.

Andreas

On Wed, May 11, 2016 at 1:33 PM, Pete Jemian <prjemian at gmail.com> wrote:

> 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 |
>> www.dectris.com
>>
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>>
>>
>>
>>
>>
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-- 
<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 |
www.dectris.com

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