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    User name Sulkosky

    Log entry time 23:52:40 on August22,2003

    Entry number 112752

    This entry is a followup to: 112681

    Followups:

    keyword=Target Polarization Loss

    After the controlled access, I performed an EPR measurement to check to see the quality of the signal in the reference cell position. The Septum current was around 383A, and correction coils C and D were on at +2.14A and -2.14A respectively. The EPR signal was noisy, but EPR did work. The polarization however was only 22.4%, since this was quite different than the 42% measured at 10 in the morning, it was hoped that there was a problem with EPR. After some calibration runs were completed, NMR was performed around 20:00. The NMR measured was consistent with the EPR measurement from 2 hours earlier. The polarization was only 25%.

    It was then decided to take some acceptance data to allow the polarization to pump up for three hours. At 23:00, the NMR polarization was 28%.

    I looked into the activities of the Day shift and found no inconsistencies with the laser, holding field, and target half waveplate configurations. Everything appears to be fine. The correct lasers were on and the holding field currents were also correct for the configurations. JP had suggested that the loss could have been caused by a jump in the holding field current during rotation, but I have looked at the plots of the coil currents, and there is no such jump. Another alternative is that when JP came out of the hall to look at the EPR signal in the Counting House, he noticed that the EPR RF function generator was on at a low frequency. It's possible that if this was on for several hours that it caused the polarization loss. I talked to Xiaochao Zheng, and she agreed that this is a likely cause for the loss. She also said she noticed earlier around the start of Swing shift that the EPR counter was displaying a low frequency. So apparently the function generator was in this configuration for at least a few hours. At the end of the experiment, we should conduct a few tests to determine the likely cause of this sudden loss in polarization.