[Nexus] NXdata for an "10-channel" high resolution detector

Wintersberger, Eugen eugen.wintersberger at desy.de
Mon Jun 10 22:59:14 BST 2013

Thanks guys for the suggestions

Currently we are storing the data like at SOLEIL. However, I would agree
with mark that a single array would be much more comfortable for
plotting. The problem with this is that we are writing data in a
record-style manner. This means at every point a new data item is
appended to the data field of the individual detectors. By doing so we
can ensure that every point data is written to disk - even if the scan
breaks accidentally. The only chance we would have is to do the
concatenation afterwards once the scan is finished. 

Seems that I have to think about which direction we would go ;)


PS: we had now the first beamtime with the new Lambda detector developed
at DESY which will natively write Nexus files. The uses had no problem
with this so far ;)

On Mon, 2013-06-10 at 16:52 +0200, Mark Koennecke wrote: 
> Eugen,
> On 06/10/2013 04:20 PM, Wintersberger, Eugen wrote:
> > Hi folks
> >    I have a question concerning NXdata. We are currently starting with
> > Nexus at our beamlines here at DESY. P02 - a powder diffraction beamline
> > - will be the first one to use Nexus.
> > They have a kind of 10-channel detector which is in reality a curved
> > detector consisting of 10 individual point detectors each having an
> > analyzer in front of them. The angular offset between the detectors is
> > about 1 degree. We store each individual detector in a separate
> > NXdetector group. The full scan data can be obtained by concatenating
> > the data and polar_angle fields of each of the 10 detectors.
> > The question is now: what should go to the NXdata group? Can I have 10
> > individual pairs of of data/(variable or x??) in a single NXdata group
> > or do I have to create 10 individual NXdata groups?
> > regards
> >    Eugen
> The plot you want from a  powder diffractometer is polar_angle versus 
> counts.
> Thus I would concatenate in the DAQ software and store that in NXdata. 
> If you
> have concerns about the concatenation done in the DAQ you can still go 
> back to
> the individual detectors. You may also wish to store the concatenated 
> data as a
> virtual NXdetector to make the relationship crystal clear.
> Regards,
>             Mark
> >
> >
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