Lamiaa and I replaced the base on PMT 17 and confirmed the performance and gain was good.
The tank was flushed with 500psi worth of a CO2 cylinder. A full CO2 tank was attached, the purge valve was closed, and pressure regulation was re-enabled. We're now running with CO2 as the radiator.
We also spent some time chasing new noise that appeared in the system (most obvious as bad pedestals). This was eventually traced to the ADC. The noise was present on the unit in slot 16 even with the signal cables disconnected. The signal cables were moved to an empty ADC in slot 17 and the noise problem went away.
NOTE: This will require a database change starting with run 5371.
Run 5360:
- HVs for 11--20 on, pulser on
- LED #5 plugged in
- Pulser amplitude sent to LED is ~1.25V, 25ns FWHM
- Checking gain on PMT 17 (replace the base)
= PMT 17 gain looks good
= lots of noise on several channels...
Run 5361:
- HVs for 11--20 on, pulser on
- LED #5 plugged in
- Pulser amplitude sent to LED is ~1.25V, 25ns FWHM
- T8 trigger dominated
- PEDESTAL run
= PMTs 18, 19 have noise
= PMT 4 looks really terrible
= lots of noise on several channels...
Run 5362:
- HVs for 11--20 on, pulser on
- LED #5 plugged in
- Pulser amplitude sent to LED is ~1.25V, 25ns FWHM
- T8(100Hz), T2(1kHz) triggers
- moved PMT 18s cables down a few rows in the front-end amplifier
= noise on PMT 18, 19 seems to have gone away
= pedestal for PMT 3 has 2 peaks: ch 70, ch 95, HV is off
= PMT 4 is very noisy (HV is off)
Run 5363:
- SAME as 5362 (running for RICH)
- T8(100Hz), T2(1kHz) triggers
Run 5364:
- HVs for 11--20 on, pulser on
- LED #5 UNplugged (so no LED pulse)
- T8(100Hz), T2(1kHz) triggers
= pedestal for PMT 3 has 2 peaks: ch 70, ch 95, HV is off
= PMT 4 is very noisy (HV is off)
Run 5365:
- prescales for RICH testing setup
- just pedestals for Cerenkov
- HVs for 11--20 on, pulser off
= pedestal for PMT 3 has 2 peaks: ch 70, ch 95, HV is off
= PMT 4 still is very noisy as expected (no changes)
Run 5366:
- HVs for 11--20 on, pulser off
- several signals seem to have a -30mV DC offset on them coming out of the FE
amplifier. It looks like this is just a 2--3mV bias from the first amp.
strapped to the beamline side Cerenkov multiplied by 10x. Not sure why
only PMTs 3,4 seem to show problems.
- moved signal for PMT 4 down to bottom row in F.E. amplifier
= same problem, no change...
Run 5368:
- HVs for 11--20 on, pulser off
- several signals seem to have a -30mV DC offset on them coming out of the FE
amplifier. It looks like this is just a 2--3mV bias from the first amp.
strapped to the beamline side Cerenkov multiplied by 10x. Not sure why
only PMTs 3,4 seem to show problems.
- fiddled with the cable into the ADC
= no change
Run 5369:
- HVs for 11--20 on, pulser off
- unplugged PMT 4 from ADC, terminated the cable to be safe
= still noise in PMT 4s ADC channel
Run 5370:
- HVs for 11--20 on, pulser off
- unplugged ribbon cable for PMTs 1--16 from ADC
= still noise in PMT 3, 4 PMT channel (even though nothing is plugged in to
the ADC
Run 5371:
- HVs for 11--20 on, pulser off
- plugged both ribbon cables in to ADC in slot 17 (was 16)
= noise is gone!
- PMT 4 was still unplugged from ADC ribbon cable, hence very narrow pedestal
Run 5375:
- HVs for 11--20 on, pulser off
- ribbon cables left plugged into ADC in slot 17
- plugged ADC 4 signal cable back into ribbon cable
= All looks good
Run 5376:
- HVs for all PMTs on (1--20)
- PEDESTAL run
= All looks reasonable