As a follow up to the excellent suggestions made by others I would suggest that a close examination of x-file headers may reveal abnormalities in e.g. crystal orientation -- suspecting an unlocked or drifting goniostat. It may also indicate a precession around the phi, which should also manifest itself in a systematic deviation of average intensities (i.e. scale factors) in a similar pattern (assuming uneven illumination of the crystal). Sometimes the precession is caused by a bubble or a tiny chunk of ice trapped under the pin, it can melt unevenly and re-align the pin a few minutes into the run (something similar used to happen a lot at one or two beam lines and it drove me nuts until I figured out the need to re-align the crystal after the initial screening).
Artem On Wed, Jun 22, 2011 at 11:22 AM, bie gao <[email protected]> wrote: > Dear Colleagues, > > I'm collecting a dataset on our recently repaired Rigaku home source. > Crystal diffracts to 2.2A. Indexing seems to be all fine. However, during > integration, I realize Y-Chi2 is increasing constantly (from 2 to 4.5, > almost linear) within 60 degree collection, whereas X-Chi2 stays the same. > An image is attached. There are still another 60 degree to go. Although the > prediction fits the images well so far, I'm afraid the Y-Chi2 will > eventually run out of the chart. > My question is could it be related to any hardware malfunctioning, i.e., > goniometer, image plates, etc, which may be a side effect of the recent > major repair? Or what else it can be? > > Thanks, > Bing >
