2018/05/29 (Tuesday)

Previous Day

0810	Tower/MC/Coldplate = 39.7/31.1/169 mK, Still = 1.06 K / 0.100 mbar, G1/G2 = 164/168 mbar, 1K Pot = 1.52±0.01 K / 7.0±1.0 mbar. MB = 73.4%
	circulation pressures have been wandering around a bit, G1 = 155-175 mbar
0815	Fill LN2 cold trap bath
0825	Filling trap bath caused a dip in tower temperature, Tower = 39.3 mK
0840	Lab = 23.4 C / 41% humidity
0845	Plug in DIB cables to HV box and plug in DCRCs:
	Setup: DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2 → gender changer 3/?/2 → HVConn 1/3/2 → HV 1/2 → DCRC55(1)/DCRC50(3)
0850	Try configuring ODB then powering DCRCs. Tower temperature climbs to 200 mK. DAQ programs don't start. Unpower DCRCs.
0855	Attempting procedure to login to cdms2 to check the status of the DAQ. But I'm getting errors:

[fritts@cdms2 ~]: sudo -u cdmssoft -s
[sudo] password for fritts: 
bash: fork: retry: Resource temporarily unavailable
bash: fork: retry: Resource temporarily unavailable
bash: fork: retry: Resource temporarily unavailable
bash: fork: retry: Resource temporarily unavailable
bash: fork: Resource temporarily unavailable
[cdmssoft@cdms2 /home/grad/fritts]: cd /home/hep/cdmssoft/scdmsDAQ/MidasDAQ/setup/umn
[cdmssoft@cdms2 ~/scdmsDAQ/MidasDAQ/setup/umn]: source midasUMN.env 
bash: fork: retry: Resource temporarily unavailable
bash: fork: retry: Resource temporarily unavailable
bash: fork: retry: Resource temporarily unavailable
bash: fork: retry: Resource temporarily unavailable
bash: fork: Resource temporarily unavailable
[cdmssoft@cdms2 ~/scdmsDAQ/MidasDAQ/setup/umn]: cd ../../online/bin
[cdmssoft@cdms2 ~/scdmsDAQ/MidasDAQ/online/bin]: ls
bash: fork: retry: Resource temporarily unavailable
bash: fork: retry: Resource temporarily unavailable
bash: fork: retry: Resource temporarily unavailable
bash: fork: retry: Resource temporarily unavailable
bash: fork: Resource temporarily unavailable

1105	Tower = 39.2 mK
1215	Got some help from IT, they rebooted cdms2. Now sudo works. Restart MIDAS DAQ
1220	Tower = 39.1 mK
1220	Plug in DCRC1: Tower rises to 170 mK. Start DAQ programs, then turn off 15V Power - Tower falls to 130 mK but then rises again to 200, then falls again…
1230	Tower seems to be cooling back to base, now at 42.3 mK.
1230	Turn off DAQ programs, then power DCRC3. No increase in temperature. With 15V Power turned off on both DCRCs, start DAQ programs.
	Turning on DAQ programs causes sudden rise in Tower temperature to above 400 mK. Turn off DAQ programs. Temperature still high, 500 mK. Disconnect power from DCRC3: temperature does not fall. Disconnect power from DCRC1: temperature starts to fall.
1245	Power DCRC3: temperature doesn't rise. Power DCRC1: temperature rises. Start DAQ programs with 15V Power enabled on DCRC1: temperature falls. 15V Power is not enabled on DCRC3.
1255	Tower = 45.0 mK, cooling
1300	Zap SQUIDs
1340	Tune SQUIDs and adjust QET biases to see pulses in all 6 channels.

DCRC1:

LockpointAdjust (mV) 	
[0] -3.6
[1] -3.8
[2] -3.7
[3] -2.5
SQUIDBias (uA) 	
[0] -85
[1] -70
[2] -85
[3] -90
QETBias (uA) 	
[0] 200
[1] 200
[2] 200
[3] 0

DCRC3:

LockpointAdjust (mV) 	
[0] -4
[1] -4
[2] -2.5
[3] -1.3
SQUIDBias (uA) 	
[0] -80
[1] -85
[2] -65
[3] -40
QETBias (uA) 	
[0] 0
[1] 150
[2] 350
[3] 300

1410	Try applying a voltage bias to the detector.

V_bias[V]	V_test[mV]
0	0
5.0	12.8
10.0	25.1
20.0	50.4
50.0	125.9
90.0	226.4
100.0	251.7
90.0	226.6

These are quite high leakages. In fact they suggest that all the bias is dropping across the ballast resistor and there is no bias on the detector.

1430	Put a purge bag around the end of the E-box and run a hose to the vent of the LN2 Dewar, open the vent a little to purge the bag. (It's pretty humid today so this will likely be necessary.)
1445	Now that bag has been purged for a bit try applying bias again, measure leakage.

V_bias[V]	V_test[mV]
0	0
5.0	12.6
10.0	25.3
20.0	50.4
50.0	125.9

1450	Test voltages are still high, we are going to try disconnecting the detector, we have turned of DAQ and powered down the DCRC's and unplugged the DIB's from the DCRC's.
1455	Dialled the bias up to 50V, the test voltage is now 3mV, must less than with everything connected.
1500	Do electrical checks on DIB 3, looking for shorts to chasis from squid, feedback, QET. No shorts found, doing the same for DIB 1
	DIB 1 also looks good
1505	Checked cross channel on DIB 1, also good
	Checking DIB 4 shorts to chasis from squid, feedback, and QET. Looks good as well.
1525	Checking for leakages from one phonon channel to another, all combinations of squid, feedback and QET. DIB 4 seems ok.
	DIB 1 also looks ok
1530	DIB 3 looks fine
1535	Try plugging only DIB1 into HV box, then apply 5V of V_bias. V_test reads -4 mV. I guess this means zero leakage. At bias 10 V, V_test is about -3 mV.
1540	Try plugging only DIB3 into HV box, then apply 5V of V_bias. V_test reads 12.65 mV. Looks like this DIB is responsible for the leak.
1540	Try plugging only DIB4 into HV box, then apply 5V of V_bias. V_test reads 12.65 mV. OK, I guess this DIB is leaky too.
1555	Use Dsub switchboard to try applying HV with DIB3, see which connections need to be turned off to stop the leakage. Tried switching off various connections… even after disconnecting all of them it still leaks! Very strange…
1620	As it turns out, simply touching the Dsub shell of DIB3 to HV connection 3 causes HV leakage. Then tried reading the test voltage on the multimeter - we had been reading it on the Keithley 617. With the isolated multimeter there's no leakage.
1623	Replace Keithley with Fluke 8600A multimeter. (Same one we've used in the last few runs). No leakage at 5V with DIB3 Dsub shell connected as above.
1625	Try plugging only DIB3 into HV box, then apply 5V of V_bias. V_test reads ~10 mV but falls to <3 mV over 1 min.
1630	Plug all cables back into HV box. Measure leakage with ~ 1 min wait after each V increase.

V_bias[V]	V_test[mV]
0	0
5.0	12 → 2.3
10.0	12 → 4.8
15.0	15 → 5.0
50.0	77 → 19

1645	Left it biased at 50V for ~10 min and the leakage fell to 9.4 mV. This is ~46V across the detector which isn't too bad! It seems like the Keithley was grounding one side of the test resistor when making a voltage measurement across it. This is because this instrument uses a (proprietary) triaxial connector which is grounding the BNC ground, instead of making a floating voltage measurement across it. That's a bummer because we were able to read out the Keithley with LabView to log the leakage current.
1656	Power up the DCRCs with 50V bias applied. A bit of heating when first powering up, but all phonon channels are still working! Set HV bias to 0 V
1702	Fill LN2 cold trap full.

Next Day