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    User name sawatzky

    Log entry time 11:24:19 on March 12, 2005

    Entry number 141298

    This entry is a followup to: 141293


    keyword=negative deadtimes

    The negative deadtimes are quite small (-5 to -2). Browsing the code in /adaqfs/home/a-onl/scaler/dtime/ suggests that the most probable culprit is a too coarse/incomplete calculation of the "corrected" triggers (intended to take correlations between triggers into account -- ie. a T5 is also a T1 and a T3).

    The upshot is that a livetime value > 1 is computed under our trigger conditions. Thus deadtime (=100.*(1 - livetime)) goes < 0.

    FWIW, the numerator and denominator of the datamon livetime calculation are each around 260, so it wouldn't take a big error/omission in the trigger correction calculations to produce what we see...

    (I know, more detail than necessary. It's been an uneventful shift :-)