[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: [ccp4bb]: Se-Met and X-ray absorption

***  For details on how to be removed from this list visit the  ***
***    CCP4 home page http://www.dl.ac.uk/CCP/CCP4/main.html    ***

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

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