[Nexus] problems with current stable of nxbrowse and nxdir

Wintersberger, Eugen eugen.wintersberger at desy.de
Fri Sep 13 17:39:30 BST 2013

Ok - here are my comments on that

> You got many things right, more then most synchrotron people as fas as I 
> can see.
> Some comments:
> 1) In NXmonochromator you appear to be defining a double crystal 
> monochromator. NeXus does not
>      yet know how to do this. Perhaps this is worth a proposal?

It definitely is. Nearly all of our beamlines use double crystal

> 2) In NXsample I found many funny named fields. Units of mm indicate 
> that they might be translations.
>      I am feeling lost: either use standard NeXus names or at least use 
> the vector, type, depends_on etc stuff
>      to annotate what this is doing.

All these non-standard names will be moved to NXcollection in the
future. After a long discussion with Ben convinced me that this is a
good idea. I am actually working on a kind of best practice paper how to
handle this situation.
What is a bit problematic that nearly none of the standard fields
defined by Nexus are directly available at our experiments. Jan (who is
implementing the Nexus data server) has now introduced functionality in
his code  that we can do simple computations on the fly during recording
data. Hopefully we can compute some of the standard field values from
the ones available at the beamline directly during data acquisition.

> 3) There seem to be many more unknown names.
> 4) I also wonder if there should not be more then one NXdata; one for 
> each detector. of which there appear to be
>     10: channel1-10 and detector proper.

This is indeed a bit tricky. I was thinking about having several NXdata
fields. But as far as I know this is not recommended. Our current
approach is to leave NXdata empty during the experiment and run some
small postprocessing code on the file afterwards which assembles the
full scan and stores it to NXdata (or better we will store the computed
data to NXprocessing and then link to NXdata). 

> Have a nice weekend,
>              Mark
> > regards
> >    Eugen
> >
> >
> >
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