Richard I think the sharp spot is just small angle scattering (e.g. from domain boundaries) resulting from the beam hitting one of the defining apertures in your collimation system. If you ray trace the beam from the last defining aperture, through the guard aperture then to the detector you should get an area of high background where the guard aperture does not cut this off and it is not covered by the beamstop. It then drops off as the beamstop comes in to play appearing to give a sharp spike. In fact, it is quite well set up with the beamstop not overly large. The appearance of a very diffuse ring for the scatter from nitrogen is due to the fact that the beamstop cuts off the air scatter, for the parts of the beam nearer the beamstop. Cheers Colin
-----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Richard Gillilan Sent: 27 November 2007 16:40 To: [email protected] Subject: Re: [ccp4bb] To bathe or not to bathe. Oops, sorry. The x axis of the previous plot is actually not resolution, but Q. My bad. Richard On Nov 27, 2007, at 11:26 AM, Richard Gillilan wrote: > Just a couple small images that may be of interest. The x scale is > resolution in Angstroms, the y scale is intensity (arbitrary units). I > don't recall if the plot is corrected for CCD pedestal values, so the > difference is not quite as dramatic as x49, still very nice clean > background if you are looking for a faint signal. > > The CCD images below are equal exposures shown with equal contrast > settings: > > <HeN2.tiff> > <HeN2imgs.tiff> <DIV><FONT size="1" color="gray">This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom </FONT></DIV>
