2021/01/22 (Friday)
- Lab in-person: Zach
- Virtual partner: Matt
| Status | Run 74 prep. 1K Pot pumped out and isolated. Fridge and 4He and LN2 Trap 1 isolated, not pumped out. Cryostat vacuum jacket pumped out. IVC open, tower installation in progress. |
|---|---|
| 1500 | Zach body temp = 99.1 |
| 1525 | Zach enters lab. |
| 1610 | Finish electrical checkout on DIBs 1 and 2. Everything looks OK except DIB1 QI bias and QO bias show 25 nS short to chassis. That suggests a short close to the detector, either at the detector itself or in the side coax, on the far side of the bias resistor. But the detector itself is not shorted, because shorts are not seen at DIB2. So a little strange that both of the charge channels on this DIB have the same short. |
| 1620 | Disconnect SQUET from DIB 1 to investigate the shorts. |
| 1625 | Look for shorts from Tower Face 2 charge-related sockets to chassis. Verify that at Tower we also see 25 nS shorts from both qI and qO bias to chassis on DIB2. This is strange. The 25 nS suggests that the short is a connection from the detector-side of the bias resistors in the side coax to chassis. But this should be connected to the other three electrodes through the detector. So we should see shorts on the DIB2 electrodes as well. But we don't. The only solution I can think of is that the DIB1 channels are no longer connected to the detector. Could be that both of the DIB1 wirebonds have broken, and that both of them are touching the housing. That would be a strange coincidence. |
| 1640 | Disconnect accessories and DIB2 SQUET from tower. Check continuity between one Q bias on DIB1 to one on DIB2. Open. Try a DIB2 charge channel to Socket 9 on Face 4 (side 2 electrode): 25 nS. So, it's verified: there must be broken wirebonds on both DIB1 channels. Could be at the detector or could be in the side coax. |
| 1645 | Start working on removing the tower. Remove SQUETS from striplines. |
| 1700 | Disconnect 4K heat sinks. |
| 1705 | Zach exits lab. |