Re: [pdDMG] DDLm pdCIF Issue 1: could detector and 2 theta offsetbe looped together in pd_calib?

one more, from yesterday

Begin forwarded message:

From: Brian Toby <toby@anl.gov>

Subject: Re: [pdDMG] DDLm pdCIF Issue 1: could detector and 2 theta offset be looped together in pd_calib?

Date: November 1, 2016 at 10:52:20 AM CDT

To: Distribution list of the IUCr COMCIFS Powder Diffraction Dictionary Maintenance Group <pddmg@iucr.org>

I put this aside for more thought originally, but I am not sure if that moment will arrive, so let me provide a few (perhaps random) comments.

One concern here is that it is common with strip and area detectors that one often collects data at different two-theta settings due to gaps in the arrays. I will skip the self-citation, but I have worked on a detector where the CCD readout is synchronized to the two-theta sweep. One would probably not try to handle raw data from that in pdCIF, but I could certainly imagine having Mythen data collected at several different 2theta settings. I guess a separate block for each could be a solution, if we so choose. 

I think that I also considered the case where the 2-theta offset could vary with 2theta. At 11-BM we do apply corrections as a function of 2-theta since we can see that the Huber deviates from ideal. 

Brian

On Oct 31, 2016, at 10:28 PM, James Hester <jamesrhester@gmail.com> wrote:

There having been no response to this, I will assume that there is limited to no demand for a multi-detector+multi-offset capability and leave the current powCIF draft as is.

James.

On 24 October 2016 at 11:23, James Hester <jamesrhester@gmail.com> wrote:

In DDL1, items in the pd_calib category can vary by detector ("loops may be used for calibration information that differs by detector channel").  Similarly, 2theta offset values can be looped where the offset varies by point.  While this is fine, it is not clear if we wish the pd dictionary to cover a situation where both detector and 2 theta offset vary, that is, for each detector in a multi-detector setup the 2 theta offset can take multiple values for different points collected by that detector.  Has anyone encountered such a situation?

If the situation is rare, but conceivable, we can create a separate 'extension dictionary' which covers this case, but mainstream software is protected from misinterpreting loops (this is a new feature).

James.

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Brian H. Toby, Ph.D.                            office: 630-252-5488

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"We will restore science to its rightful place, and wield technology's wonders... We will harness the sun and the winds and the soil to fuel our cars and run our factories...  All this we can do. All this we will do."

********************************************************************

Brian H. Toby, Ph.D.                            office: 630-252-5488

Advanced Photon Source Chief Computational Scientist

Senior Physicist/Computational X-ray Science Group Leader

9700 S. Cass Ave, Bldg. 401/B4192                 cell: 630-327-8426     

Argonne National Laboratory        

Argonne, IL 60439-4856         e-mail: brian dot toby at anl dot gov 

********************************************************************

"We will restore science to its rightful place, and wield technology's wonders... We will harness the sun and the winds and the soil to fuel our cars and run our factories...  All this we can do. All this we will do."