The problem is best seen in the width of the "double-difference", which is the difference between charge asymmetry measured in two independent BCMs. This is a measure of resolution, and expect for non-linearities in the measurement, is independent of the actual beam jitter.
The jumps in measured beam current noted in Wouter's entry (208446) must be part of the problem, but they aren't the whole problem. I couldn't reproduce those plots (run number wasn't noted) and didn't happen to see any similar, apparently false spikes in beam current. But the attachment is the double-difference plotted vs. pattern number. One can see noise come and go, which isn't healthy in a device that requires high resolution. It is clear that the noise is not isolated to short intervals.
Attachment 1: Run 7534 (today, PC off)
Attachment 2: Run 7409 (11/21 afternoon) DD=197ppm
Attachment 3: Run 7389 (11/21 early morning) DD=453 ppm
DDvsTime_Run7534.png
DDvsTime_Run7409.png
DDvsTime_Run7389.png
