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    User name R. Michaels

    Log entry time 11:14:34 on June16,2000

    Entry number 43920

    keyword=new T4 (no S0), min required rate

    T4 is now the logical OR of S1,S2 counters, because S0
    was taken out. Indeed we took access and unplugged the
    cables that had taken S0 L,R PMTs to the 2nd MLU, to
    avoid any confusion.

    For the record, we unplugged the following from MLU2.
    Yellow twisted-pair cable into input 4 from 4518 delay module
    output 13, slot 4 of CAMAC. Green cable input 5 from
    output 12.

    Here is a rule of thumb for how many T4 to keep in the datastream.
    First we assume that the global inefficiency is ~2%. Next we assume
    that in 12 hours we want to measure it to at least 2% accuracy. Let
    T3=scaler-rate-of-T3, T4=scaler-rate-of-T4, and T4-keep=rate
    of-T4-written-to-tape.
    The fraction of T4 which are not junk is approx 2% * T3/T4.
    So, we need T4-keep * 12-hours * 2% T3/T4 = 1/(0.02)**2
    Solving, we get the rule of thumb:
    T4-keep (Hz) = 3 * T4/T3... <<<--------- RESULT
    For example, if T3=1 kHz, and T4=10 kHz (typical, I imagine),
    we need to keep 30 Hz of T4 after prescaling. Because a lot of
    them are junk.