2022/04/18 (Monday)
- Lab in-personnel: Matt, Nikki
| Status | Run 76 in progress |
|---|---|
| Setup | Cables currently disconnected, DCRC33(2)→HV control, NaI trigger signal → DCRC52(6) |
| 1020 | Continuing to investigate HV short seen with the Side2-readout HV board… |
| saw a short in Cable 2 last week. This short is at a Side2 channel so this should affect the Side1-readout board. But we are also seeing a short with the Side2-readout board | |
| today I'm finding that if Cable 1 and 3 are both plugged in, there's a short, but if either is plugged in alone there is no short. This can only mean that each of these cables produces a short to some intermediate point, and both together are needed to produce the full short…. | |
| 1115 | Use a diverter board and DIP switches to narrow down which Cable 1 wires complete the short. Conclusion: Cable1 QET Return D is the culprit. With these 4 wires disconnected, then plugging Cables 1 and 3 in shows no short at the HV lead. |
| 1135 | Look for Cable 3 connections that are shorted to Cable1 QET Return D by plugging Cable 1 into breakout box and going pin-to-pin on Cable 3. It's Cable3 QET C and QET C return. |
| 1140 | Check Cable 3 at breakout box, don't see any QET shorts to chassis |
| So we know we have Cable1 pD shorted to Cable3 pC. This is Side1pF shorted to Side1pA. This makes sense - I was worried that these two channels were shorted because a Side1pA stadium was used as a hopscotch pad for Side1pF, and I wondered whether the surgery to disconnect the pad from pA was sufficient… apparently not. Measured the short: 1.78 MOhm. |
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| This still doesn't explain the HV short seen when Cables 1&3 are simultaneously connected to the Side2-readout HV board, because no channels on these cables show shorts to chassis. | |
| 1200 | Check resistance at HV connector with only Cable 2 plugged in - no short. |
| Putting the pieces together… it seems that there can't be a cold-side short from one of these two phonon channels to chassis, because in that case either one of the cables alone would produce the short. Another detail of interest: to break the short on Cable 1, I needed to disconnect the four QET D Return lines - but NOT the QET D line. But QET and QET Return are connected on the cold side. This seems to suggest a short on the warm side… | |
| 1450 | MC/Coldplate = 26.2/140 mK, Still = 1.04 K / 0.100 mbar / 0 mW, G1/G2= 127/117 mbar, 1K Pot = 18° / 1.58 K / 11±1 mbar, MB = 32.8% |
| 1450 | Goldman = 66.4 mK @ 632 uV excitation |
| 1455 | Fill LN2 cold trap bath |
| 1506 | Begin LHe transfer @ MB = 32.5% |
| 1520 | Studying the Side2-readout HV board… I think I was making a mistake with the cables! Viewing from the front, from left to right, I had Cable 2/1/3 connected. It's supposed to be Cable 2/1/3→CONN 1/2/3 on the HV board inputs. But the connectors on the HV board/card are numbered 1/3/2 from left to right! So from left to right it should be Cable 2/3/1. |
| 1530 | Plug Cables 2/1/3 → HV CONN 1/2/3, correctly this time. Measure resistance at the HV input: <0.5 nS. Good! |