Rob and I lowered the threshold on the main detector event mode discriminator in the cage from 30.2 mV to 20.5 mV. This is going from something like 1.5-2.0 photoelectrons to 1.0-1.5 photoelectrons.
We also decreased the HV on the MD4+ tube from 1150 V to 1100 V. Note that prior to this change ~50% of the total 16-tube OR rate came from md4+. The photoelectron distribution on the scope in the cage changes from a mean of about 10 mV to 7 mV (taking approximately the half-max of the p.e. distr.) That tube no longer dominates the rate wildly by itself, but the rates still differ from bar-to-bar as is shown below. The MD3bar rate is noticeably higher than it was at 30 mV threshold.
Bar AND (Hz) OR (Hz) 1 50 13000 2 20 5500 3 300 115000 4 130 80000 5 45 20000 6 50 14000 7 50 19000 8 20 15000
The total 8-bar trigger (previously known as the AND-OR trigger, but we're phasing that name out to avoid ambiguity) is about 750 Hz. This is the rate recorded by taking the AND of two tubes on a bar, and the OR-ing all 8 bars together.