Gerard, Good evening.
We actually used the vertical gap for the P300K because we found the vertical gap worked well enough with the extra module providing better coverage. The strategy algorithms we developed use a minimal number of 2theta settings and fill in missing data with different phi and chi or kappa settings. I can see where allowing the same sort of flexibility in 2theta settings might improve the speed and completeness of coverage. I'll look into it. Thank you for taking the time to think about it. Cheers, Joe Ferrara -----Original Message----- From: Gerard Bricogne [mailto:g...@globalphasing.com] Sent: Sunday, July 16, 2017 5:24 AM To: Joseph Ferrara <joseph.ferr...@rigaku.com> Cc: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Pilatus Issues Dear Joe, On second thought, it seems to me that a vertical gap would be even better suited to the use of a 2theta axis than a horizontal one: if one assumes that the 2-theta axis is parallel to the Omega axis, i.e. vertical, a small 2-theta offset by at least the angular width of the gap would suffice to fill it completely, as it would essentially amount to a horizontal translation. With a horizontal gap, a 2theta offset mostly slides the gap into itself, and therefore rescues fewer reflections from having fallen in the gap at 2theta.eq.0 . I am probably missing some fine points that you looked into more thoroughly. With best wishes, Gerard. -- On Sun, Jul 16, 2017 at 09:24:41AM +0100, Gerard Bricogne wrote: > Dear Joe, > > Thank you for the insights :-) . Near-exclusive exposure to > synchrotron beamlines leads one to forget about 2theta axes, as they > are hardly ever encountered; but indeed it is a help here. Most of > all, I would assume that your default strategies would use several > *crystal* orientations thanks to your quarter-Chi goniostat. That > would of course help fill the gap since it amounts to tilting it, but > even so, it still feels as if more low-resolution reflections would be > lost because of their proximity to the rotation axis than if the gap > was mounted vertically. Is that actually not the case? > > > With best wishes, > > Gerard. > > -- > On Sun, Jul 16, 2017 at 06:19:01AM +0000, Joseph Ferrara wrote: > > 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 > > >
