Unfortunately the Cerenkov PMTs are not in individual scalers. I worked around this by only turning on 1 PMT HV at a time and looking at the Cerenkov-Only trigger (T7). I have remote control over the threshold on that discriminator as well.
The T7 trigger also sees the EDTM pulser, so there is rate even with all the HVs off (first table). Fortunately (sort-of), the EDTM rate is negligible compared to the rates with HV on.
'PMT 19' is the witness PMT in a dark box, not the Cerenkov PMT.
The background rates are ridiculously high. Qualitatively, it is worst at the top of the Cerenkov and worse still on the the beamline side. Those observations match with Xin's observations focusing on the MWDC analysis. The uppermost PMTs 1,11 see less rate than those right below them (ie. PMTS 12,13). PMTs 2,3 (near top, beamline side) aren't functioning properly -- given the rates in adjacent PMTs on the beamline side, I think it is a good bet that the bases have been damaged by radiation.
All data were taken with a nominal 12uA incident on the He3 target.
Trigger rates:
107. kHz T1 rate
1.3 kHz T3 rate
0.050 kHz T5 rate
23.3 kHz T6 rate
Started 10:30pm, Sunday night, run 3573
T7 rates w/ all HVs off (ie. EDTM pulser only, same as T2 rate)
Thresh Rate (Hz)
-100 12.48
-300 12.48
-500 12.48
-700 12.48
-750 12.48
-800 0
-900 0
------ RHRS side -------
T7 rates w/ HV on 11 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 142.
-300 33.3
-500 18.7
-700 11.8
-900 7.4
T7 rates w/ HV on 12 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 450.
-200 151.
-300 78.6
-400 33.2
-500 9.5
-700 12 Hz (EDTM rate?)
-900 0 Hz
T7 rates w/ HV on 13 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 314.
-300 121.
-500 45.0
-700 27.3
-900 17.3
T7 rates w/ HV on 15 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 429.
-300 156.
-500 55.3 (~100 Hz during abeam trip)
-700 34.2
-900 24.7 (~10 Hz during a beam trip)
T7 rates w/ HV on 16 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 241.
-300 117.
-500 64.3
-700 40.0
-900 26.4
T7 rates w/ HV on 18 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 409.
-300 99.4
-500 37.3
-700 25.4
-900 18.5
T7 rates w/ HV on 19 on (witness PMT @ 2100V); 11.8 uA beam
Thresh Rate (kHz)
-100 168.
-300 48.6
-500 17.6
-700 11.8
-900 8.8
T7 rates w/ HV on 20 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 281.
-300 85.1
-500 30.0
-700 17.9
-900 11.4
------ Beamline side -------
T7 rates w/ HV on 1 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 2285.
-300 803.
-500 311.
-700 208.
-900 148.
-1V 124.
T7 rates w/ HV on 4 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 3315.
-300 1287.
-500 814.
-700 596.
-900 436.
-1V 374. (~100 Hz during trip)
T7 rates w/ HV on 5 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 4218.
-200 3386.
-300 2210.
-500 987.
-700 478. (~200 Hz during trip)
-900 183.
-1V 118.
T7 rates w/ HV on 10 on (real PMT); 11.8 uA beam
Thresh Rate (kHz)
-100 2817. (~10 kHz during trip)
-300 1035.
-500 413.
-700 278.
-900 198.
-1V 167.
Done 11:30pm, Sunday night, run 3574