[Imgcif-l] additional dictionary items to map marccd exposure, integration, readout times?

[Chris Nielsen]

	Hi Herbert & Michael,

	I agree with the adding additional fields to record the
"different" versions
of time.  I do the same thing as Michael does with accumulation time and
so forth.  The comment about use in diagnosing beam line timing problems
is
especially on point.  Even after a beam line is technically
"commissioned"
you still want this info since problems can reappear at a later date as
"routine"
work is performed on the control software.

	Chris


-----Original Message-----
From: imgcif-l-bounces at iucr.org [mailto:imgcif-l-bounces at iucr.org] On
Behalf Of Michael Blum
Sent: Tuesday, October 14, 2008 8:54 PM
To: The Crystallographic Binary File and its imgCIF application to image
data
Subject: [Imgcif-l] additional dictionary items to map marccd
exposure,integration, readout times?


marccd (the program)  measures and records 3 elapsed times for each data
frame.

They are:

exposure_time     - the time elapsed during which the shutter was open.
integration_time   - the time elapsed during which the detector  
accumulated signal
readout_time       - the time elapsed during which the detector was  
being read.

The original motivation to keep these times in the header was to
facilitate correcting for dark current accumulation, which occurs on a
CCD during the integration time and, with a different shape, during the
readout.

In practice, our detectors have such low dark current that this
correction hasn't been necessary, BUT the recorded times have turned out
to be very useful for diagnosis of beamline hardware, detector hardware,
and beamline-detector synchronization problems.

Currently, when writing CBF files, I can only store one of these
numbers.  I store the "exposure" time in
diffrn_scan_frame.integration_time

I would like to propose that the other times be added to the
diffrn_scan_frame category, but I don't know what to propose for the
names, since there is already a conflict between the current dictionary
and my naming convention.

Possibly:
integration_time
detector_integration_time
detector_readout_time

or
integration_time
accumulation_time
readout_time


regards,

Michael

_______________
Michael L. Blum                    Toll Free: 877-627-XRAY (627-9729)
Rayonix, LLC                        Tel: 847-869-1548
1880 Oak Avenue                 Fax: 847-869-1587
Evanston, IL  60201              Email: blum at rayonix.com
USA                                       WWW: www.rayonix.com





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