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    User name X. Zheng

    Log entry time 19:01:16 on June 7,2001

    Entry number 62381

    This entry is a followup to: 62379

    keyword=Correction to rate/time of 3He elastic asymmetry measurement

    The "total time" 19.5 min in run #1438 end-of-run file is the total time. Real beam time is about 0.17*19.5=3.315minutes. Or average beam current is 1.7 microAmp.

    So the estimation for 3He elastic asymmetry is:

    Prescale factor: 4
    Rate: pres/real
    Window: 1103Hz / 4412 Hz
    3He total: 596 Hz / 2382 Hz
    3He elastic: 40 Hz / 158 Hz

    So we are back to 13.3 hours (effective 8.0 hours) for 3%, exactly the same as the run plan.

    However, we are going to move the HRS momentum higher (from 1.168 to 1.191, 2% higher) to get rid of the huge QE peak. This helps to reduce the total rate (basically from window and QE) by roughly a factor of 2, but keeps 3He elastic rate unchanged. So the suggested setting/estimation for 3He elastic asym is:

    Prescale factor: 2
    Rate: pres/real
    Window: 1103Hz / 2206 Hz
    3He total: 596 Hz / 1191 Hz
    3He elastic: 80 Hz / 158 Hz

    Then we need 9.4 hours (effective 5.64 hours) to finish 3he elastic asymmetry.