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Hi Eugen & Pete,<br>
If you want to move the "usage" field into NXmonochromator, then
maybe we should rethink NXmonochromator and consider a larger
overhaul. We currently have the "crystal" and "velocity_selector" as
optional fields for hard X-rays and neutron, respectively, and I
want to add "grating" to that set of optional fields for the soft
X-ray case. For soft X-rays, the situation is actually even more
complicated as the geometry set by entrance and exit slits are also
a fundamental part of the monochromator (and the entrance slit is
also optional, since some beamlines simply consider the source size
and position stable and small enough).<br>
Can you think of a better way to achieve all this? One option would
be to set it up so that one looks at the "usage" field first and
then uses its value to decide which optional fields to looks for
next. This would mean including values such as "grating" and
"velocity_selector" in the list of possibilities for the "usage"
field, which would then make the name "type" more appropriate.<br>
<br>
Cheers,<br>
Ben<br>
<br>
<br>
<div class="moz-cite-prefix">On 09/03/15 21:41, Eugen Wintersberger
wrote:<br>
</div>
<blockquote cite="mid:1425933715.1770.10.camel@desy.de" type="cite">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">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.
</pre>
</blockquote>
<pre wrap="">
I entirely agree with you here. However, this is a particular use case
for a crystal in connection with a monochromator. Thus, at least in my
opinion, the "usage" field belongs to NXmonochromator.
</pre>
<blockquote type="cite">
<pre wrap="">
On 03/09/2015 03:14 PM, Eugen Wintersberger wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi Pete
On Sun, 2015-03-08 at 11:48 -0500, Pete Jemian wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Eugen:
You propose to:
* rename "usage" field to "type"
</pre>
</blockquote>
<pre wrap="">
I propose to remove the "usage" field entirely from NXcrystal.
</pre>
<blockquote type="cite">
<pre wrap="">* add "channel_cut" as another possible value
</pre>
</blockquote>
<pre wrap="">
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.
</pre>
<blockquote type="cite">
<pre wrap="">
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.
</pre>
</blockquote>
<pre wrap="">
This would be the "type" field for NXmonochromator. It should identify
what type of mono we talk about.
</pre>
<blockquote type="cite">
<pre wrap="">
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?
</pre>
</blockquote>
<pre wrap="">
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
</pre>
<blockquote type="cite">
<pre wrap="">
Pete
On 3/8/2015 10:56 AM, Eugen Wintersberger wrote:
</pre>
<blockquote type="cite">
<pre wrap="">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
</pre>
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</blockquote>
</blockquote>
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<pre wrap="">
</pre>
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