[Nexus] Beamline description using Nexus

Koennecke Mark (PSI) mark.koennecke at psi.ch
Mon Jan 22 15:17:17 GMT 2018

Dear Heike,

> Am 22.01.2018 um 15:06 schrieb Heike Görzig <heike.goerzig at helmholtz-berlin.de>:
> Hi,
> I am Heike Görzig working at HZB in Berlin in a BMBF financed project on
> data management with focus on metadata.
> To begin with, I want to describe the BESSY II beamlines using nexus. As
> starting point we found useful using the XML file generated by the
> simulation software RAY-UI, which is available for many beamlines at
> At the beamlines at BESSY II we are using gratings quiet often.
> NXgrating is defined as a base class in the Nexus definitions, but I
> can't create a NXgrating using nexpy or nexusformat in python3. Normally
> it should be possible, or am I wrong here?

You create a new group and give it the type NXgrating. Then add fields matching the 
description of NXgrating. 

> The other question I have, might be a bit out of scope of the intention
> nexus was created for, but I believe some of you might have run into the
> same challenges and it would be great to get advices from you and not
> adding more variety to the list a common challenge can be dealt with.
> There are three very concrete questions:
> In the simulation software the size of e.g. a mirror or grating is very
> important as well as the slope error, but therefore I can't find
> anything in the nexus definition. Has someone of you managed this?
> The other question I have is about the layers in mirrors. For substrate
> and coating there is a roughness defined, but not so for the layers.
> Otherwise, the coating is lacking a thickness. Has someone tackled this?

NeXus, by tradition, has been very neutron centric. It can very well be that there are fields missing, as Ben
spreads stated. Make a suggestion to the NIAC. 

> The next question is more general, if someone of you has created an
> application definition for describing beamlines at their facility and
> how are you relating the beamline description to an experiment?

See Bens reply.

I want to add that there is a NIAC representative for HZB in Berlin. He is at the reactor and his name 
is Jens Uwe Hoffmann. His email is hoffmann-j at helmholtz-berlin.de If you are beginner with NeXus your fastest 
path forward might be to meet up with him and discuss your problems at an example with him.

Best Regards,

     Mark Koennecke

> Thank you,
> Heike
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