2021/03/21 (Sunday)
- Lab in-person: Derek
- 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) for the last couple days, other channels look fine | |
| 1320ish | MB = 61.6% |
| 1310 | Tower = 94.9 mK |
| 1315 | DCRC1qI noise still bad. 1500 e-6 @ 10 kHz |
| 1424 | Derek enters lab. |
| 1426 | Tower/MC/Coldplate = 94.4/36.4/169 mK, Still = 1.16 K / 0.130 mbar / 0 mW, G1/G2 = 371/344 mbar, 1K Pot = 1.67 K / 8.5±2 mbar. |
| 1430 | MB = 58.0% |
| 1431 | Fill LN2 cold trap bath. |
| 1445 | Power down both DCRCs and unplug the cables from the DCRCs. We'll check the bad channel at the breakout box. |
| 1450 | DIB1 qI Feedback to Chassis is short, 25.8 nS. Other ones are OK. Note that this channel showed a bit of a short at 77K as well, 12 nS. |
| 1500 | Reconnect and repower DCRC3. Leave DCRC1 disconnected, Cable 3 plugged into breakout box. |
| My hunch is that helium in the IVC is making the short worse. The short is apparently on the FET gate line, either at SQUET or side coax or somewhere between. Let's warm up enough to pump out some helium, see if the short gets better. | |
| 1510 | Close V6 to stop circulation |
| 1515 | After V6 closes completely (and Still rising, Condenser falling) close 1K Pot needle valve. Note - maybe this time we'll leave speedivalve open, so that the 1K Pot gets pumped dry. |
| 1515 | Tower temperature rising, → 0.11 K |
| 1515 | Turn on MC heater → 10 mW. Tower temperature rises faster. |
| 1520 | Tower = 1.0 K and rising. Check DIB1 qI Feedback to Chassis again, the short is still 25.8 nS though maybe a bit less stable. |
| 1530 | Tower = 1.8 K, rising more slowly now. Condenser = 188 mbar and falling. 1K Pot has fallen → 1.53 K / 6.5 mbar. |
| 1700 | Tower = 2.2 K and flat. Condenser = 70 mbar and settling. 1K Pot = 1.54 K / 6.5 mbar, unchanged. |
| 1705 | Increase MC heater → 20 mW |
| 2035 | Tower = 2.2 K, did some oscillating and had one spike to 2.6 K. Condenser = 67 mbar, went up a little at the spike. 1K Pot = 1.53 K / 6.5 mbar, unchanged. |
| 2230 | MB = 47.2% |