No signal on PMT 12
- Current draw on the associated HV channel is comparable to the rest of the
PMTs so perhaps a broken connection at the feedthrough?
- Confirmed that PMT 20 assembly did have a signal.
- Shut off HV, opened the purge valve and increased the CO2 flow rate. Then
swapped the entire PMT assembly for 12 with 20 (PMT assembly for #20 was
installed but has no focusing mirror). This procedure only took a few
minutes.
- Cabling stayed the same so I swapped the nominal HVs in the GUI 12 <->
20 to
follow the PMT.
C4F8O work
- Installed the new CGA 716 nipple on the pressure regulator.
- Put the C4F8O bottle up on the scale (initial reading 245 lbs).
- Attached the regulator and checked for leaks using Snoop.
- Note:The bottle pressure is very low and doesn't register on the
high
pressure gauge. Max pressure observed on the low pressure side when outflow
valve shut was 10--15psi.
- Set the flow rate to 15--20 cfph mark on the flowmeter. This appears to be
roughly 5 lbs/hour. 1 kg is roughly 100 liters (STP) so this should be about
230 liters/hour (~8 cfph).
- Tank is 1800 liters so a single volume swap will take ~8 hours at this rate
(want to see 200lbs on the scale: 40lbs == ). Don't want to crank the
flow up
too much or I'll freeze the valve and liquefy the gas. Patience.
- I'll check on the valve in a couple of hours...
Cerenkov group disc. threshold
- Changed the discriminator offset back to -10mV on the front panel
(reverting my
earlier change). This put the threshold at -100mV. Updated the offset
for the
BB_Cer channel in the threshold_BB software to match.
- Set the BB_Cer threshold to -150mV using the software.
v792 Filters
- The current CAEN filters seem to do a poor job of taking out a DC bias
on the
input signal. (We observed a +5mV bias coming out of the amplifier when the
PMT was under load in testlab. The signal looked great when we took the bias
out using the offset pot. on a linear fan... Next access I will try swapping
them out with the simple capacitive filters used for the 1881s.