2021/03/13 (Saturday)
- 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/nothing → DCRC50(3)/ |
|
| 1056 | MB = 27.6% |
| 1115 | Tower = 89.6 mK |
Todo list for today:
- With Cable 3 still plugged into the breakout box, check for shorts from Side2, qI Bias, and qO Bias to ground. Should be < 1 nS.
- Power down DCRC1, disconnect it from minibob, then plug Cable 3 into the HV diverter board and into DCRC1. (We'll skip the source mover board just in case that one was introducing problems.) Power up DCRC1 again.
- Try biasing Side2 with the Kepco supply like we did yesterday, but this time using the HV BNC on the diverter board. Last time we tried that we got catastrophic noise - maybe this time will be ok…
| 1355 | Derek enters lab. |
|---|---|
| 1357 | Tower/MC/Coldplate = 88.5/35.1/180 mK, Still = 1.39 K / 0.130 mbar / 0 mW, G1/G2 = 382/339 mbar, 1K Pot = 1.69 K / 40±2 mbar. |
| 1405 | Check for shorts to ground. Side2/Qibias/Qobias = 0.1/9/10.5 ns. Actually with the other cable still plugged into the DCRC, we can't test for shorts - because two of the channels are grounded, so what we're seeing is continuity from one channel to another. |
| 1435 | Plug Cable 3 into HV diverter board and plug diverter board into DCRC1(55) (after powering down DCRC1 and disconnecting it from the minibob). |
| 1450 | Having a lot of trouble getting DCRC55 to power on while it is connected to the diverter board. It goes on fine if disconnected or connected to the minibob. It shuts off as soon as the DSub connector touches. |
| 1500 | Remove Gender Changer 3 from Cable 3, replace with an unlabeled one. Doesn't help, DCRC still won't come on. |
| 1530 | With DCRC1(55) powered but not plugged into anything, we noticed that connecting a wire from the other DCRC Dsub shell to DCRC55's shell made a spark and caused the power to go off. We tried measuring the DC voltage between the DCRC55 shell and the readout cable shell and it reads 55 V. We tried connecting to the DCRC with MIDAS and turning off the 15V power and saw a very small change in that voltage. Derek pushed down on DCRC55's Dsub shell while measuring that voltage and it fell to 0 V. So I guess something is shorting the POE power to the DCRC ground and you need to push on the Dsub to break that short. Or something like that. |
| 1545 | Fill LN2 cold trap bath. |
| 1613 | Start LHe transfer @ MB = 18.5% |
| 1635 | Tried blowing the DCRC with N2 gas. Tried plugging into the minibob, then HV diverter board, measured the voltage to ground - generally seeing 0V though with some manipulation could get it to go to 50V again. Plugged Cable 3 into the HV diverter board, and it stayed powered. |
| 1647 | End LHe transfer |
| 1652 | MB = 90.1% |
| 1705 | Check noise in the charge channels: DCRC3qI/qO/DCRC1/qI/qO = 3.2/2.1/6.9/2.5 e-6 @ 10 kHz. Not too bad. |
| 1715 | Plug HV lead into 0-40V Kepco power supply set to 0V. No increase in noise - good! |