SLD Data Logging Guidelines

SLD should log data whenever luminosity and beam conditions are at all reasonable. If conditions deteriorate to the point where little or no useful data is being written, logging should be stopped until the situation improves. This ultimately comes down to a judgement call by the run coordinator.

Some guidelines for what constitutes acceptable logging conditions are collected below:

     GOOD BEAM CONDITIONS       BAD BEAM CONDITIONS

     luminosity > 20 Z/hr       luminosity < 10 Z/hr
     livetime > 95%             livetime < 90%
     trigger rate < 0.5 Hz      trigger rate > 1 Hz
     veto rate < 0.5 Hz         veto rate > 2 Hz
     event size < 250K          event size > 500K
     CDC occupancy < 10%        CDC occupancy > 20%

Check out the 120 Hz trigger statistics displays (documented in "Rules of the Game") for additional diagnostics.

What to do when beam conditions are bad

Check that beam conditions really are the problem,
rather than SLD trigger, FASTBUS, or calibration problems.
Consult with SLD liaison and SLC operators and program deputy,
get them to call in a background expert if necessary.
If beam conditions are very bad, end run and stop logging data,
ramp down CDC and CRID high voltages.

Eric Vella / vella@slac.stanford.edu,
based on guidelines collected by Stan Hertzbach