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    User name Cates

    Log entry time 23:20:28 on February 28, 2006

    Entry number 164542

    keyword=Calibration of target polarimetry, target polarization, and procedures for polarized running

    A calibration of the polarimetry system was performed between roughly 18:30 and 22:00, and is described in detail on pages 132-137 of the target log book. The calibration constant was measured twice, roughly two hours apart. The first measurement yielded 0.445 %/mV, and the second 0.440 %/mV. For consistency, I suggest we use 0.442 %/mV as the working number. While this number is probably good at around the 10% level, no corrections have been made for systematic errors that we know are present at some level. Thus, we should not be too surprised if the calibration changes by more than this amount as we refine our measurement.

    At around 9PM, the target polarization was approximately 30% and rising. We should all be VERY CAREFUL to avoid doing things that might cause depolarization.

    As mentioned in a sign hung near the target computer, no EPR of any sort, with or without flips, should be performed. No exceptions. AFP should be performed no more than once per two hours. Try to time it so that it comes immediately before running with the He-3 target. If there is no need to perform AFP in order to know the polarization during a run, AFP should be performed no more than once every six hours.

    To be clear, if a run is being initiated using the He-3 target, and an AFP has not been performed in the last two hours, do an AFP measurement. Simply ask the shift leader to hold off on starting the run until you are done. If it has been less than two hours since the last measurement, do not do an AFP measurement. If you hit the six hour mark without having made a measurement, do one anyway.

    Finally, all AFP measurements should be recorded in the HALOG. If something more complex has happened, such as the polarimetry calibration reported in this entry, you can simply summarize what happened so long as the details are recorded in the target log book.