Don Walko asked me to replot the data I had plotted last night, suggesting
there would be something interesting to see on Sunday night between 10pm and
6 am. The data shown below starts at 9h19 pm on Sunday 6/27 and last 9 hours.
The time axis is in hours from the starting time of 11h19m19s on 6/24 so 82
hours corresponds to 21h19m19s on 6/27.
Attachment 1 shows the APS XBPM data from P1 and P2, extrapolated to the
plane of the L5-20 slit, 26.5 m away from the source.
Attachment 2 shows the 7ID-C X-ray BPM data. Note the horizontal beam motion
in both plots corresponds to the earthquake that occured around 1h15 am in
Ottawa IL, about 70 miles from Chicago. The 7ID-C and APS horizontal position
moves by about 75 and 6 um respectively. The 7ID-C is less sensitive to the
motion because the L5-20 slit is closed to a 500um horizontal opening, thus
the full beam does not pass through the slit. If the slit does not move with
respect to the floor, the center of mass of the beam in 7ID-C does not move much.