[NeXus-committee] Proposal for NXcrystal and NXmonochromator

[Pete R Jemian]

I see.

The choice of Bragg or Laue orientation is important when calculating 
the rocking curve profile, whether or not the crystal is used as part of 
a monochromator.

On 03/09/2015 03:14 PM, Eugen Wintersberger wrote:
> 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
>>>