[NeXus-committee] Additions to NeXus

Andreas Förster andreas.foerster at dectris.com
Wed May 11 12:15:51 BST 2016

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*

o   *name*: *NX_CHAR*

§  Name of synchrotron

o   *@short_name*: *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*

o   *name*: *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*

§  Two-dimensional array of FWHM (if Gaussian) or diameters (if top hat) of

o   *profile*: *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 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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