Gerard, You are correct that a vertical gap is best when 2theta.eq.0 and we did explore orienting the Pilatus with the gap vertical early in the hardware integration process. However, we concluded that when 2theta.ne.0 at least two 2theta settings would be required to prevent systematically missing resolution shells. Since most data sets are collected with 2theta.ne.0 we decided on the horizontal gap in order to distribute the missing data evenly. Please note the direct beam is not in the gap so low resolution reflections are accessible.
I would also like to point that a loaner detector was provided to John a few days ago and we are working with Dectris to sort out the issue that began this discussion. Cheers, Joe Ferrara -----Original Message----- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Gerard Bricogne Sent: Saturday, July 15, 2017 4:31 PM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Pilatus Issues Dear John, Having just seen Andreas's message regarding the best source of support to address your enquiry, I have a further remark to make about your instrument. As this is a lab instrument, the Omega axis would be vertical, and indeed the beam stop shadow (vertical on the top module) and the diffuse shadow of the sample holder (vertical on the bottom module) would confirm this. This being the case, it is quite simply *daft* to have the gap between the two modules being horizontal. That is done on purpose on synchrotron beamlines because of the polarisation of the beam (which is why Omega is horizontal on such beamlines), but in a lab system the gap should be in the vertical direction. As currently placed in your system, this gap is cutting into perfectly good data, whereas if it were vertical instead, it would only cut out data that are getting perilouly close to the cusp anyway. You should ask the manufacturer of your diffractometer to rotate your detector by 90 degrees! Someone in the OEM world forgot about the Lorentz factor ;-) . With best wishes, Gerard. -- On Fri, Jul 14, 2017 at 05:14:03PM +0100, John Hardin wrote: > Hi, > > We have recently noticed an issue with our Pilatus (biased pixels/vertical > lines). > I was curious as to whether anyone else has seen this or might know what > could have caused it? > > Best, > John >
