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User name D. Parno
Log entry time 15:02:15 on March 3,2009
Entry number 264328
This entry is a followup to: 264201
keyword=No change in Compton asymmetry after 2/18 half waveplate switchIn the linked entry, we noted a drop in the Compton asymmetry and hence measured beam polarization that coincided with the half waveplate going IN on February 28. We looked at the previous half waveplate change in more detail and confirmed that it did not have a significant effect on the measured Compton asymmetry.
These figures track the Compton asymmetry and (extremely approximate) beam polarization for a period around the last half wave plate switch during owl shift on February 18 (this switch happened just before run 15823, where the red and blue asymmetries flip sign). The asymmetries plotted here span the time from late owl shift February 16 (~48 hours before the change) to early owl shift February 22 (just under four days after the change).
It looks as though the fact that the polarization dropped on Feb. 28 at around the same time as the HWP changed was a coincidence. The polarization drop was probably due to a change in accelerator balance.
FIGURE 1
FIGURE 2
