Am 20:59, schrieb Harry Powell: ...
I think there may be issues with collecting data too finely with a Pilatus, even in shutterless mode. I don't know where the problems arise (can't be shutter/rotation axis synchronisation), but it seems to be the normal thing in XDS (which should have no problems with fine phi-slicing) to use the "PATCH_SHUTTER_PROBLEM=TRUE" that Martin Hallberg suggested, which looks a bit like a fudge to me (but I expect Kay to correct me on that!).
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Hi Harry,no, it is a misunderstanding that the normal thing is to use PATCH_SHUTTER_PROBLEM=TRUE in XDS; rather, it may be the last resort to try before you abandon a dataset, and if the spindle/shutter de-synchronization is so poor that this fudge needs to be used, then the BL hardware needs to be fixed before other datasets are collected.
Two other points:a) one may distinguish "weak data resulting in high R-factors" from "problems with hardware or radiation damage resulting in high R-factors" by looking at (I/sigma)^asymptotic as defined in Acta D66, 733 ( http://dx.doi.org/10.1107/S0907444910014836 ). b) Marcus Müller (SLS) has shown (to me, unambiguously) that the best data are obtained from the Pilatus if delta-phi is 1/2 to 1/4 of the mosaicity (as reported by XDS). However, for the best data, other parameters of the experiment (basically the transmission and the spindle speed) have to be optimized as well. The finding of Tassos that 0.5-1 degree data gave the best result in a particular case might indicate that these other factors of his experiment were not optimal (it is indeed not trivial to get them right).
best, Kay
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