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

[Wintersberger, Eugen]

Hi Carlos 

On Tue, 2013-06-11 at 08:32 +0200, Carlos Pascual wrote:
> Hi Eugen,
> 
> are you using Sardana  foracquiring and  writing the data?

We are not using Sardana yet, though it is already installed on the
beamline computer. We will move towards Sardana during the long shutdown
in autumn. 

> 
> If so, it should be possible to create a custom recorder that writes the 
> concatenated data on-the-fly.

Sure - one can always write custom IO code. I just wanted to know if
there is an easier solution ;) 

regards
  Eugen

> 
> Carlos
> 
> On Mon 10 June 2013 23:59:14 Wintersberger, Eugen wrote:
> > 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 ;)
> > 
> > regards
> >   Eugen
> > 
> > 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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> > > 
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> 

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