[NeXus-committee] Proposal for NXcrystal and NXmonochromator

[Eugen Wintersberger]

Hi Pete

On Sun, 2015-03-08 at 11:48 -0500, Pete Jemian wrote:
> Eugen:
> 
> You propose to:
> * rename "usage" field to "type"

I propose to remove the "usage" field entirely from NXcrystal.

> * add "channel_cut" as another possible value

And I propose to add a "type" field to NXmonochromator. The possible
values for "type" could be "Laue", "Bragg", "Pseudo Channel Cut", and
"Channel Cut". Or something in this way. 

> 
> As I said before, "channel_cut" is not an alternative to "Bragg" or 
> "Laue" in its description of crystal orientation.  Most channel cut 
> crystals use Bragg orientation.  I suggest a new field could be added to 
> describe "channel_cut".  Another similar term could be 
> "pseudo_channel_cut" which describes the crystal arrangement of most 
> synchrotron X-ray monochromators.

This would be the "type" field for NXmonochromator. It should identify
what type of mono we talk about.

> 
> Like many things in NeXus, the field name "usage" does not seem to fit 
> so well, as you point out.
> 
> Rather than disrupt the historical use of the "usage" field in NeXus 
> data files and however many data files have been written with this 
> field, would it be acceptable to improve the documentation for the 
> "usage" field?

In the best case I would declare it as deprecated. At least from my
point of view NXcrystal describes a crystal and not its particular
application. But we can leave it there for compatibility reasons and
declare it as deprecated. 

I am not sure if, what I propose, is really the best approach. But for
the time being I have no better idea how to deal with the situation. 

regards
  Eugen
 

> 
> Pete
> 
> On 3/8/2015 10:56 AM, Eugen Wintersberger wrote:
> > Hi folks
> >    as a result of the recent discussion I would like to propose the
> > following changes to NXcrystal:
> >
> > remove the "usage" field from NXcrystal
> >
> > It makes no sense there as the way the crystal is used in a particular
> > application is entirely unimportant for the particular crystal itself.
> >
> >
> > Furthermore I would like to suggest the following change to
> > NXmonochromator
> >
> > add a "type" field to NXmonochromator
> >
> > This field should basically hold the values of "usage" from the current
> > NXcrystal class. I would also suggest to have an additional possible
> > value "channel_cut" available for this field.
> >
> > Best regards
> > Eugen
> >
> >
> >
> > _______________________________________________
> > NeXus-committee mailing list
> > NeXus-committee at nexusformat.org
> > http://lists.nexusformat.org/mailman/listinfo/nexus-committee
> >
> 

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