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    User name R. Michaels

    Log entry time 11:26:39 on July17,2005

    Entry number 148320

    keyword=counting mode with Helium4

    Initial alignment and checkout

    HV det3 (R-arm) 1700 V
    HV det1 (L-arm) 1850 V

    Rates for I = 0.5 uA

    L-arm HAPPEX detector 6 kHz
    S0 PMT1 2 x 10^5 Hz
    S0 PMT2 2.8 x 10^5 Hz
    R-arm HAPPEX detector 3460 Hz
    S0 PMT1 4.6 x 10^5 Hz
    S0 PMT2 5.2 x 10^5 Hz

    T1 = 4.5 x 10^5 Hz
    T2 = 3400 Hz
    T3 = 1.4 x 10^5 Hz
    T4 = 6300
    T5 = T6 = 0
    T7 = 5.8 x 10^5 Hz
    T8 = 6.0 x 10^5 Hz

    Run 2098 - At the "nominal" momentum setting, to check detectors, etc
    Ooops ! VDC HV was off. Well, that's why we have checklists...

    Run 2099 Repeat, with VDCs on. Noticed one S2m was off. Turned
    it on.

    Fig 1 shows the ADC spectra for the 2 HAPPEX detectors
    using the above-written HV settings.
    There is a peak seperated from pedestal; this was filled for
    triggers 2 & 4 respectively (the pedestal is identified for
    other triggers). We could bump up the HV some more ...

    Increasing HV on HAPPEX Dets
    Det1 (L-arm) 1850 -> 1900 Volts. Rate went from 6 kHz to 36 kHz
    Det3 (R-arm) 1700 -> 1800 Volts. Rate went from 3.3 kHz to 38 kHz
    (oops, this was done at about event#400K of run 2099, we forgot
    to stop the run).

    Run 2100 -- Another detector check.
    Fig 2 shows detectors (different X axis now).

    Now decreasing magnetic field to 2.653 (2 % low).



    FIGURE 1

    FIGURE 2