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User name D. Parno
Log entry time 17:18:22 on March 6,2009
Entry number 264946
keyword=Compton Asymmetry at 4-Pass TodayFig. 1 shows the Compton asymmetry measured in an 80-minute run today at 4-pass. We measure an asymmetry of about 4.5% at the Compton edge. Based on the calibration to the Moller at 4-pass, this yields an approximate beam polarization of about (56 +/- 1)% (statistical error only).
Because the photon detector response will be somewhat different at 4-pass energies than at 5-pass, using the 5-pass calibration introduces some systematic error into the beam polarization number quoted above. After the Moller run taking place right now, we will have a 4-pass calibration point to help alleviate this problem.
Rates this afternoon (prior to the Moller) look very good. (That's the blue line in Fig. 2).
FIGURE 1
FIGURE 2
