The offset issued was determined to be the input saturation of the PI box. Increasing the lock-in sensitivity from 500uV to 1mV solved the problem.
The new calibration constant is quoted from the second measurement which has a higher precision (relative error ~ 1 %).
The polarization after 2 EPR measurments is about 60%
A copy of this log entry has been emailed to: jpchen@jlab.org, chiran@jlab.org, jinhuang@jlab.org, jkatich@jlab.org, zhangyi@jlab.org
EPR Sweep #1
EPR AFP #1
EPR Calibration #1
EPR Sweep #2
EPR AFP #2
EPR Calibration #2