2018/06/29 (Friday)
| overnight: DCRCs off, cooling to base | |
| 0430 | Tower = 30.2 mK, G1/G2 = 62/73 mbar, Still = 0.055 mbar, 1K Pot = 1.38 K / 2.0 mbar 1K Pot has fallen extremely low, will fail at some point soon, maybe see if it can last until I get there in the morning. Will check again and suspend circulation remotely if necessary. |
| 0630 | Tower = 30.4 mK, G1/G2 = 61/73 mbar, Still = 0.055 mbar, 1K Pot = 1.38 K / 1.9 mbar 1K Pot stopped oscillating at 5:00. But so far circulation pressures are OK. |
| Tower temperature rose last night from 29.1 to 30.1 mK as 1K Pot ran lower and lower, then after tweaking the pot late last night it fell to 29.0, then rose again 30.6 when we tweaked it again at 8:15 this morning. | |
| 0810 | Tower = 30.6 mK, G1/G2 = 60/71 mbar, Still = 0.050 mbar, 1K Pot = 1.36 K / 1.7 mbar |
| 0815 | Open 1K Pot needle valve additional 20 degrees. 1K Pot spikes to 1.78 K / off-scale, then comes down again. Circulation/still pressures increase. Tower temperature begins to fall. |
| 0830 | Tower/MC/Coldplate = 29.0/28.8/159 mK, Still = 1.07 K / 0.090 mbar, G1/G2 = 92/102 mbar, 1K Pot = 1.61 K / 22 mbar. MB = 44.3% |
| 0835 | Turn on Still heater to 1 mW. This caused another spike in the 1K Pot temperature & pressure |
| 0855 | Tower = 28.8 mK, Still = 0.100 mbar, G1/G2 = 99/110 mbar, 1K Pot = 1.62 K / 24 mbar. |
| 0918 | Tower = 28.7 mK, Still = 0.100 mbar, G1/G2 = 94/105 mbar, 1K Pot = 1.58 K / 13 mbar. Seems stable. |
| 0920 | Fill LN2 cold trap |
| 0952 | Tower = 28.5 mK, Still = 0.095 mbar, G1/G2 = 93/104 mbar, 1K Pot = 1.56 K / 11 mbar. |
| 0954 | Increase Still heater → 1.5 mW |
| 1005 | Turn on DCRCs and start DAQ programs. Tower spikes to 210 mK then starts falling. Falls to 40 mK in 5 minutes |
| 1015 | Tower = 32.2 mK, still falling |
| 1025 | Tower = 31.1 mK and flat. |
| 1034 | All channels were left at 0 QET bias from a SC noise data set. Set all 6 QET biases to 500 uA to snap. Then, one by one apply QET biases from 20180601. These are (290/270/315)/(140/315/310) uA. Tower rises to ~32 mK. |
| 1040 | Pulses seen on all channels except DCRC1PB. It remains ADC railed outside of driver offset range. Re-locking doesn't help and (non-)inverting causes it to be railed (low) high. Strong oscillations are seen on DCRC3PC. |
| 1041 | Tower seems stable at 31.9 mK |
| 1044 | Zap SQUIDs using DCRC UI Zap tool. |
| 1056 | Tower peaked at 44 mK, now flattish at 30.9 mK |
| 1058 | Now we can see pulses on all channels including DCRC1PB! |
| 1115 | Adjust QET biases to reduce oscillations at 0V. |
| 1125 | Start 5-min data series with HV = 0 V, QET bias = (280/260/305)/(135/290/300) uA, Driver Gains=2, FEG=10, 1000 BOR randoms, triggering on DCRC3 PB/PC/PD = 8/16/16 ADC |
| 1130 | Tower = 30.0 mK and stable :D |
| 1134 | Start 5-min SC data series with HV = 0 V, QET bias = (0/0/0)/(0/0/0) uA, Driver Gains=2, FEG=10, 1000 BOR randoms, 20 HZ in-run randoms, triggering on DCRC3 PB/PC/PD = 8/16/16 ADC |
| 1144 | Start 5-min Normal data series with HV = 0 V, QET bias = (500/500/500)/(300/500/500) uA, Driver Gains=2, FEG=10, 1000 BOR randoms, 20 HZ in-run randoms, triggering on DCRC3 PB/PC/PD = 8/16/16 ADC |
| 1155 | Use FlashAndFlash tool to start 5 min mini-bake. Tower heats to 400 mK |
| 1230 | Tower = 31.7 mK and cooling |
| 1231 | Start 60-min data series with HV = 0 V, QET bias = (280/260/305)/(135/290/300) uA, Driver Gains=2, FEG=10, 1000 BOR randoms, triggering on DCRC3 PB/PC/PD = 8/16/16 ADC |
| 1258 | Bring PuBe source into lab and place on west side of shield. Dump sizes for current run increased from ~90 MB to ~145 MB after bringing in PuBe source |
| 1301 | Fill HPGe dewar from large LN2 dewar. |
| 1320 | Tower = 30.0 mK and flat. 1K Pot = 1.46 K / 4.5 mbar. 1K Pot has been drifting down steadily. |
| 1340 | Power on Keithley and HP multimeters. Channels seem okay still. With Kepco supply powered off, plug HV bias banana cables into Kepco +/- terminals. DCRC3PC rails, but is recovered with a re-lock. |
| 1345 | Turn on Kepco supply to 0V by ensuring DCRC4Q[0]=10.76, then setting DCRC4Q[1]=2 . DCRC3PC rails, but is recovered with a re-lock. |
| 1348 | Set HV = 70 V by running the sequence changeHV_0_70.msl while watching DCRC3PC pulse viewer. All channels remain locks and offsets. |
| 1358 | Start 142-min PuBe data series with HV = 70 V, QET bias = (280/260/305)/(135/290/300) uA, Driver Gains=2, FEG=10, 1000 BOR randoms, triggering on DCRC3 PB/PC/PD = 8/16/16 ADC Stopped data at 16:23 before starting LHe transfer. |
| 1403 | Leakage voltage has settled around 50 mV, so we're getting a 20V drop across the bias resistor. We've had the LN2 purge on the e-box for a few hours, but it is crazy humid out today. Open the LN2 vent valve a little more. |
| 1417 | Leakage voltage = 36.0 mV and decreasing linearly at ~1mV/min. All channels still look good. |
| 1442 | Leakage voltage = 25.3 mV and levelling out. This is still ~10V dropped across bias resistor. Open LN2 vent a little more. |
| 1455 | 1K pot has fallen to 1.42 K / 3.20 mbar. Open 1K pot needle valve +10 degrees. Tower spikes to 34.5 mK, then starts falling back down. |
| 1630 | Begin LHe transfer @ MB = 32.9% |
| this represents the 3rd attempt to transfer without pre-blowoff using the Dewar-side extender as suggested by Paul Crowell. We start by inserting partially into the Dewar, then as soon as gas can be felt flowing out of the cryostat-side, insert the Cryostat side partly into the cryostat (the o-ring coupling is up at the top of the stick, so some gas will leak out the top). Then lower the extender into the Dewar until the recovery meter starts moving fast, then wait 1 minute, then lower the extender further, then wait less than a minute, until the bottom of the cryostat-side is starting to get frosty. Then lower the cryostat-side all the way and seal it, and lower the Dewar-side so the extender is close to the bottom and the cross-tube is approximately horizontal. | |
| After beginning transfer, Tower spiked a little, to 32 mK, then settled back to previous level. 1K Pot spiked too and circulation pressures fell. | |
| 1730 | Tower = 30.0 mK, G1/G2 = 68/86 mbar, Still = 0.080 mbar, 1K Pot = 1.47 K / 5.5 mbar. |
| 1730 | Open 1K Pot needle valve additional 15 degrees. Temperature spikes to 1.79 K, pressure off-scale, then both fall again. Tower spikes to 31.8 mK then falls. |
| 1735 | Fill LN2 cold trap bath |
| 2106 | Turn down HV bias and flash using sequence changeHV_70_0_thenflash.msl |
| 2300 | Tower = 29.7 mK, G1/G2 = 106/115 mbar, Still = 0.085 mbar, 1K Pot = 1.51 K / 6.5 mbar |