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RE: [ccp4bb]: Se-Met and X-ray absorption
- To: "Ccp4" <ccp4bb@dl.ac.uk>
- Subject: RE: [ccp4bb]: Se-Met and X-ray absorption
- From: "Bernhard Rupp" <br@llnl.gov>
- Date: Wed, 16 May 2001 08:54:42 -0700
- Importance: Normal
- In-Reply-To: <C11370B71A8AD411B26E000102A349D8171539@exchange04.dl.ac.uk>
- Sender: owner-ccp4bb@dl.ac.uk
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Dear All -
of course I stuck my foot into my mouth on this one - the calculation
of the spread is wrong 1.0 - 0.0005 is NOT .9005 dah...I had already a
bad feeling - thx to Pierre for actually reading my blurb and
finding that mistake. Consider that even the Cu natural line width
at 8keV is 2.6 eV which has no practical effect on point spread.....
Bart pointed out that 3rd generation sources fry the crystal dead
anyhow so why bother - that is true, I was admittedly more thinking
along maximizing weaker sources like small Compton sources (a electron
bunch is 'wiggled' by a laser) which, using the broader bandwidth,
may begin to compare well to synchrotron sources.
Correction of the same calculation of 0.1% bandwidth spread
at 1A (1.0005 to 0.9995 <-!) leads to 0.02 deg (0.4 mrad) in
2theta which is negligible as it should be. So even wider
bandwidth ranges would be possible for flux gain in the
scenario I described. Problem solved.
Thx again, BR
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Dr. Bernhard Rupp
Macromolecular Crystallography and Structural Genomics
LLNL-BBRP L448 Phone (925) 423-3273
University of California Phax (925) 424-3130
Livermore, CA 94551 email br@llnl.gov
URL http://www-structure.llnl.gov
TB Structural Genomics Consortium http://www.doe-mbi.ucla.edu/TB
EU Mirror http://www.dl.ac.uk/CCP/CCP14/ccp/web-mirrors/llnlrupp
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