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    User name D. Parno

    Log entry time 13:39:10 on February 27, 2009

    Entry number 263694

    This entry is a followup to: 262392

    keyword=Beam polarization estimate from Compton

    Examining Compton data from between 10:15 p.m. last night (Feb. 26) and 11:50 this morning (Feb. 27), I've arrived at a rough beam polarization estimate of approximately 75%.

    The figures plot Compton asymmetries/beam polarization as a function of run number. This is a decent proxy for time, since each run lasted approximately two hours. Run 16085 (the first run) was shorter, which is why its error bar is larger.

    All error bars are statistical only. I have not accounted for any systematic errors within the Compton.

    Fig. 1 shows the maximum Compton asymmetry computed separately for the left-polarized laser state and the right-polarized laser state. These are approximately symmetric about zero, as they should be.

    Fig. 2 shows the magnitude of the Compton asymmetry, averaged over left and right polarization states.

    Fig. 3 shows an extremely rough polarization estimate resulting from these asymmetries. We are not yet equipped to report absolute polarizations with the Compton (we need a better detector response function for this). In order to arrive at this polarization estimate, I used a cross-calibration to the Moller measurements taken Feb. 11 and Feb. 19 (in the linked post). However, this is an imperfect calibration: the Compton measurements could not be taken simultaneously with the Moller measurements and the absolute beam polarization may have shifted between the two measurements.

    A copy of this log entry has been emailed to: brads, vasulk, camsonne

    Figure 1

    Figure 2

    Figure 3