2020/09/12 (Saturday)
- Lab in-person: Zach
- Virtual partner: Matt
| Setup | Run 73. DIB 1/3/4 → Stripline 43/48/41 → pi-filters 1/2/3 → Cable 3/1/2 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1)-master; DCRC33(2) → HV control. DCRCs on overnight. Lead/poly shield erected (4 lead walls, 2 poly walls). |
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| 0810 | Cooling after source move last night, Tower = 54.3 mK. |
| 0840 | Most channels are railed. Relock them and adjust offsets. This alone causes the temperature to drop. |
| 0845 | Currently there is spiky noise, overtriggering at threshold=8, some spike-triggers at threshold=10. Let it cool some more. |
| 0844 | MB = 68.0% |
| 0900 | At threshold=9 it's about 50-50 spike/good triggers. Tower = 52.6 mK and cooling, but looks like it's slowing down. |
| 1010 | Tower = 51.6 mK. At threshold=9 there are still spiky triggers. Looks like 75/25 good/spiky, but maybe just the same as before. Let's zap, for the heck of it. |
| 1015 | Zap SQUIDs, DCRC1&4 |
| 1040 | Tower = 51.7 mK and cooling. 7/50 triggers are spiky at threshold=9. |
| 1115 | Tower = 52.4 mK - it has gone up. And it's 25/50 spiky triggers at threshold=9 now. Annoying. |
| 1120 | Fix one railed channel, adjust others. 6/16 spiky at thresh=9 |
| 1145 | Tower = 52.7 mK. It's still rising. 2/12 spiky at thresh=9. |
| 1215 | Tower = 55.1 mK, rising. Note that because of the 1K Pot situation, Still pressure is quite low, 0.050 mbar. Maybe try heating still. |
| Notice that 1K Pot temperature and pressure have strange pulsing pattern now. About every 5 minutes there's a spike. Min is 2.2mbar/1.39K, spike is around 4.2mbar/1.47K. | |
| 1220 | Turn on Still Heater → 5 mW. Still→0.12 mbar. Condenser pressure rises, 200→270mbar and rising. 1K Pot stops pulsing for some reason, →3.4mbar/1.43K. Tower rises to 57 mK then falls to 54.6 mK then rises a little, settling around 55 mK. Seems like the DCRCs are still heating it. |
| 1235 | Zap SQUIDs again. |
| 1255 | Tower stuck at 57.5 mK, yuck. Turn off Still Heater |
| 1320 | Tower = 60.5 mK. Just keeps getting worse. Hopefully when we adjust the 1K Pot later things will improve. |
| 1355 | Tower = 59.0 mK. It's falling slowly, still pretty high tho |
As mentioned yesterday, there was a big drop starting around 3pm in the 1K Pot temperature/pressure. So far it does not seem to have failed - condenser and still pressures fell (a pot failure would probably make condenser pressure rise). But it's concerning. It generally suggests that the inlet at the needle valve suddenly became more constricted. We should open the needle valve today an additional 10 degrees, get the pressure back to something more normal.
| 1340 | Zach body temp = 97.9 |
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| 1344 | MB = 61.5% |
| 1358 | Zach arrives at lab. |
| 1402 | Opened needle valve by 10 degrees. P2, 1K pot temp spiked. G1, G2, tower temp rising. |
| Tower → 75 mK | |
| 1419 | 1K pot settling at around 10 mbar 1.57 K, turning needle valve another 10 degrees. P2 and 1K pot temp spiked. |
| Tower → 78 mK | |
| 1433 | Unplugged DCRCs. Tower temperature rises, → 81 mK, then falls a little, → 80 mK |
| 1436 | Begin LN2 transfer. |
| 1449 | 1K pot settled to about the same values. Opened needle valve another 10 degrees, P2 and 1K pot temp spiked. |
| 1450 | Ended LN2 transfer. Tower rises → 82 mK after about 10 minutes. |
| 1454 | Tower/MC/Coldplate = 79.5/32.3/179 mK, Still = 1.23 K / 0.075 mbar / 0 mW, G1/G2= 230/244 mbar, 1K Pot = 1.63 K / 20±2 mbar. |
| 1500 | Plugged DCRCs back in. Zap SQUIDs. |
| After zap Tower settles to 85 mK | |
| 1505 | Zach leaves lab. |
| 1507 | Tower rises → 91 mK, possibly because of the HV glitch (see below) |
| 1520 | Tower falls back to 84 mK |
| 1520 | The HV shot up to 500V. Troubleshooting: turns out that somehow the ODB changed DCRC2 to RevC.1 (3.1) instead of RevC (3.0), as sometimes happens. So when we restarted the programs the qI/qO settings were no longer correct. Got it back to normal. |
| 1530 | Tower = 88 mK |
| 1530 | HV and Vtest are small and negative, even though the polarity is positive. Possibly because the detector is charged up now. Let's flash the detector (cuz why not). |
| 1530 | Flash DCRC1 LEDs for 30 seconds. |
| 1550 | 1K Pot has fallen to 5mbar/1.49K. So it's approaching it's previous low value, even after opening the needle valve a lot more. Condenser/Still = 245/0.065 mbar. |
| I suspect there are two problems: 1) the change in 1K Pot temperature caused the superfluid He in the IVC to move around, so now we are having troubles with the base temp, and 2) some partial plug of the 1K Pot. If it were only 1), we could do a partial warmup like last time, just enough to evaporate He and pump out the IVC. But if the 1K Pot is a problem, that would be an air or water ice issue, and we have to warmup up basically to room temperature. Hmm. | |
| 1555 | Tower = 87.5 mK. Check channels - actually look pretty good, although of course pulse amplitudes are low. Unrail one of them. Tower temp starts falling a little. |
| Let's take some data even though it's way hot - just to get some data a the new source position. | |
| 1601 | Start a 60 min series at HV = 0V, CDMS detector: Driver Gains = 1x, DCRC4/1 QET biases = (0,320,370,0)/(0,360,420,410)uA, Front-End Gains = (3/3/3)/(5/5/5) 1000 BOR & 5 Hz in-run randoms, trigger on DCRC1pD threshold = 8 Use sequence SimpleDataLoopNoFlash.msl |
| 1601 | Tower = 85.4 mK |
| Temperature not very stable during series: around 86 mK for 15 min, then drops to 83 mK and stays around there for 15ish minutes, then rises to around 89.5 mK for 5-10 minutes, then steadily falls to 84 mK at end of series. |
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| Temperature instability messes up the 0V data |
| 1755 | Tower spikes up to 100 mK. Then starts falling slowly. |
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| 1945 | Tower has continuously fallen, now at 74 mK |
| These meanderings certainly seem like the helium-film problems we had before. | |
| 2130 | Tower = 62.5 mK. It has been falling. |
| 2135 | DCRC1pD is extra spiky. Maybe this particular temperature is bad for this QET bias. |
| 2235 | Tower = 61 mK. Spikiness bad. I guess try a zap. |
| 2235 | Zap SQUIDs, DCRC1&4 |
| 2315 | Tower = 60.6 mK. Still quite spiky. Let's take data anyway. |
| 2324 | Start a 60 min series at HV = +100V, drifting 0.0274 V/s, prebias 15% for 2min, CDMS detector: Driver Gains = 1x, DCRC4/1 QET biases = (0,320,370,0)/(0,360,420,410)uA, Front-End Gains = (3/3/3)/(5/5/5) 1000 BOR & 5 Hz in-run randoms, trigger on DCRC1pD threshold = 14 Use RootSequencer.c, function drift_sequence(100,0.0274) |
| 2324 | Tower = 60.5 mK |
| 2324 | Vtest = 3.8 mV shortly after drift begins. Drift appears to start at +106.8 V. 1.4% HV loss. |
| 2424 | Drift ends, no apparent lag. Vtest = 5.5 mV. HV at end of drift looks like 204.9 V, indicating 1.1% HV loss |
| 2424 | Tower = 58.8 mK, fell consistently (with wiggles) during series |
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| temperature instability didn't cause too big a problem | 0mm not shown because there was a railed channel in that series |