They remind me of the fiber bundle on optic taper between the phosphor and the CCD. That's from things I saw years ago (BC - before crystallography) and I don't know the system in use here. I suspect it's instrumental and any diffraction in that area of the detector should show similar effects if there is a reflection there. Have you checked more images?
This also gave me a great excuse to break out my newly arrived Atlas of Optical Transforms (thanks A.) and look at some more exotic explanations :) $5 from Amazon. Consider a spherical crystal .... :) Cheers, Eddie. From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of James Holton Sent: Friday, October 29, 2010 7:04 PM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Strange spots The shape reminds me of the focused beam spot profile from slightly misaligned capillary optics. I don't have too much experience with these, but the incident beam profile does tend to "propagate" through to the spots on the detector. I wonder, could what you are seeing be a "halo" of minor incident beams, all converging on the sample, but at very different angles from the main beam. what you would see then is a "circle" of diffraction patterns around the usual pattern, but each at effectively a different crystal orientation (because the "halo" beams come in at different angles). This would explain why the effect only seems to be apparent for spots that are close to (but not "at") the Bragg condition. What kind of x-ray setup is this? -James Holton MAD Scientist On 10/29/2010 9:08 AM, David Goldstone wrote: Dear All, Does anyone have any insight into what the circles around the spots might be? cheers Dave
