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    User name R. Michaels / B. Moffit

    Log entry time 17:50:07 on May 05, 2009

    Entry number 271070

    keyword=re: deadtime story

    Diagnosing the deadtime problems on R-HRS. Bryan in cnt room, Bob at home.

    There seem to be two problems:

    1. T8 appears to be multiple-pulsing at the trigger supervisor. This started happening
    very recently. The result is a data file with typically 2/3 of T8 despite a ps8=65k !
    It implies an astronomical rate like 39 MHz. But T8 at scalers is ok (1024 Hz, and yes
    I looked at raw counts). Minimal solution is to unplug this T8, but it's worth looking
    with a scope too.

    2. Before problem #1 started, we had a high deadtime. These seem related to ROC8
    missing-gate events. All modules missing. I don't think this has to do with buffering
    but we were not able to do the comparison of buff vs unbuff because problem #1 started
    to happen which obscures everything. It appears that ~5% of events have missing gates
    and the timeout loop parameter is 10K = approx 10 msec (!!), so at 500 Hz you expect
    DT = 500 * 0.05 * 0.01 sec = 25%, about what was seen. One really simple thing:
    reduce the timeout to 200 like we use elsewhere. But ultimately we ned to figure out
    why we have missing gates on ROC8 (the HAND crate).