• Main INDEX
  • Monthly INDEX
  • PREV
  • NEXT

    User name gilman

    Log entry time 10:49:40 on May 3,2002

    Entry number 2510

    This entry is a followup to: 2301

    keyword=FPP event sizes

    Bob Michaels warned us that the FPP event size appears to be about 1.7 kB,
    and leads to significant dead time increase (at high rates).

    Mark Jones and I recalled that we had this problem a few years
    ago when someone unplugged the level shifter power without
    telling us. The few mV noise fluctuations at the TDC inputs
    led to transitions and apparent high FPP data rates,
    unaffected by FPP high voltage and thresholds.

    The FPP level shifter crate downstairs was indeed turned off.
    Now it is on and the cosmic ray rates are about 8 events per s
    leading to about 8 kB/s. So it should be okay now to leave the
    FPP in the data stream.

    The spectrometer hut doors are closed, and nothing else was touched,
    so we should (as regards this) be good to go when the target is fixed.