2021/03/20 (Saturday)
- Lab in-person: Zach
- Virtual partner: Matt
| Status | Run 74 in progress. |
|---|---|
| Setup: DIB1/2+acc → SL 41/43 → 3.2 MHz filters → cables 2/3 → nothing/HV_diverter_board → DCRC50(3)/55(1). Kepco 0-40V supply → HV BNC. No lead/poly shield. | |
| Terrible noise in DCRC1qI (q4) since yesterday, other channels look fine | |
| 0615 | DCRC1qI noise still bad. 340 e-6 @ 10 kHz |
| 0620 | MB = 35.8% |
| 0715 | Tower = 92.4 mK |
| 0715 | Start a 5-minute mini-bake with DCRC1&3 LEDs. Tower peaks at 0.8 K. |
| 0725 | Noise in DCRC3qI/qO/DCRC1qI/qO = 1.8/1.4/370/2.6 e-6 @ 10 kHz. Tower = 0.42 K, cooling. No change in noise really. |
| 0730 | Turn on MC heater → 10 mW. We'll try heating it that way. |
| This caused a runaway increase in condenser pressure after a minute, so I turned it off again. Also causes a spike in the 1K Pot pressure. Tower peaked @ 1.2 K | |
| 0735 | Noise in DCRC3qI/qO/DCRC1qI/qO = 1.7/1.5/350/2.4 e-6 @ 10 kHz. Tower = 0.91 K, cooling. Still no change in noise. |
| 0740 | G1 (condenser) = 585 mbar and falling. It was 380 mbar before the MC heating. It peaked around 700 mbar before I turned off the heat. |
| 1155 | DCRC1qI noise still bad. 390 e-6 @ 10 kHz |
| 1200 | Turn off 15V power on both DCRC1 and DCRC3. Let's leave these off a while, maybe the FETs will cool off and something will change. In this state the noise in each channel is around 1e-6 @ 10 kHz and there are no high frequency peaks. Interestingly this seems to cause a Tower temperature increase, 93.0→94.5 mK. |
| 1320 | Tower = 87.2 mK and cooling. Significantly colder than this morning, so having the 15V power off makes a difference. |
| 1325 | Turn 15V power back on on DCRC1&3. This causes the channels to rail. Interestingly I got them to unrail by turning on Enable FET Heater for half a minute, then they came back. Then I turned that off again. (In ordinary running conditions turning this on or off doesn't seem to do anything. I think when you first enable the DCRC it turns on the heater for a bit, then when it gets warm enough the FET self-heats.) Sadly the noise in DCRC1qI is still just as bad. |
| Either the 15V or the FET heaters caused Tower temperature to spike to 170 mK. It's cooling quickly. | |
| 1330 | Noise in DCRC3qI/qO/DCRC1qI/qO = 1.7/2.5/450/2.4 e-6 @ 10 kHz |
| 1420 | MB = 21.8% |
| 1510 | Tower/MC/Coldplate = 91.7/37.1/190 mK, Still = 1.46 K / 0.130 mbar / 0 mW, G1/G2 = 376/337 mbar, 1K Pot = 1.68 K / 40±2 mbar. |
| 1515 | Troubleshooting noise. Disconnect HV supply - no change. Tighten cable into diverter board. This introduced a big high frequency noise spike (1 MHz) that didn't go away. Power off DCRC1, remove diverter board, plug cable directly in, repower. |
| 1525 | Noise in DCRC1qI is still bad. Actually worse. We were able to get rid of the 1MHz noise by tightening the connection on the other DCRC (3), but the noise on DCRC1qI is particularly bad, hitting the rails a bit. For now: unpower and unplug both DCRCs. Let them rest for a bit. |
| 1541 | Begin LHe transfer @ MB = 20.0%, Pressure in dewar started high ~8psi, not sure why. (turns out it's because it was filled higher than we are used to, 217 L.) |
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| 1550 | Begin filling LN2 cold trap dewar. |
| 1602 | Ended LN2 transfer. |
| 1619 | Ended LHe transfer @ MB=87.1% |
| 1645 | Plug in DCRC cables again and power up DCRCs. (Didn't include diverter board.) Noise is still bad in DCRC1. We also saw the 1 MHz spike but messing with the DCRC3 connection seemed to pretty much fix that. |
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| 1655 | Noise in DCRC3qI/qO/DCRC1qI/qO = 1.9/1.9/1290/7.6 e-6 @ 10 kHz. So the noise in DCRC1 is about 3 times worse than before, DCRC3 unchanged. |