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    User name R. Michaels

    Log entry time 15:55:00 on December18,2008

    Entry number 253915

    keyword=R-HRS P0 scan.

    During run 20183 a few days ago I thought I saw 100 Hz with
    magnets off. So I'll try to repeat this.

    Reminder, T8 = S1.and.S2 = what we used to call T1

    Runs 50633 (pvdis) and 20211 (R-HRS) start with P0=600 MeV/c.
    At the following events we make the following changes to P0.
    Beam current is 11.8 uA. (The T8 rate takes into account
    the factor of 2 due to 2 helicity scalers.)

    pvdis DAQ .... R-HRS DAQ .... P0 .... observed T8 rate
    6100 ...... 1400 .... set to zero .... 12 Hz
    15000 ..... 5000 .... dipole reaches 0.580 ... 12 Hz
    29400 .... 11500 .... 0.523 (I=126) ..... 14
    45600 .... 19000 .... 0.417 (69.3 A) .... 20
    59000 .... 21800 .... 0.31 (21 A) ..... 26 Hz
    72000 .... 39500 .... 0.21 (2A) ...... 26 Hz
    See (**) below.
    100000 ... 59000 .... 0.12 (2A) ...... 26 Hz
    123000 ... 76000 .... 0.09 (2A) ...... 24 Hz

    The DAQ rate is ~22 Hz, so the climb is roughly
    consistent with the observed T8 rate.

    (**) Saw a beam trip. Looks like the rate with beam off is
    4 to 8 Hz (this is normal for cosmics) and with beam on
    it's 22 to 26 Hz.

    Tentative conclusions:

    1. Cosmic rate is normal (T8 = 4-8 Hz)

    2. With P0=0.6 GeV we see virtually no increase with beam on
    versus off (11.8 uA corresponds to 4 Hz additional rate).

    3. Reducing P0 to zero increases T8 rate, but the 100 Hz I
    thought I saw before was not reproducible for unknown reasons.