2022/11/10 (Thursday)
- Lab in-personnel: Matt
| Status | Run 76 in progress |
|---|---|
| Setup | Cables 2/3/1 → diverter/nothing/nothing → Side2-readout HV CONN 1/3/2 → HV 1(L)/2(R) → DCRC50(3)/DCRC55(1), DCRC33(2)→HV control, NaI trigger signal → DCRCX(4) Lead/poly shield fully assembled. Boron-filled socks covering NaI detectors. PuBe behind lead wall on W side of fridge. NaI scan in progress, not set up for coincidence data |
| Cooled to base two days ago after twenty-first 5K pumpout. | |
| 0855 | MC base = 29.5 mK. Most spikes peak below 33 mK, some above 36 mK |
| 0855 | Baselines for DCRC1pA/B/C/DCRC3pA/B/C = -0.800/-0.798/-0.797/-0.798/-0.799/-0.797 V |
| 1155 | MC/Coldplate = 30.1/150 mK, Still = 1.11 K / 0.110 mbar / 0 mW, G1/G2 = 139/145 mbar, 1K Pot = 60° / 1.58 K / 10.5±0.5 mbar, MB = 41.1% |
| 1200 | Baseline for DCRC1pA = -0.799 V |
| 1205 | Fill LN2 cold trap bath - partial. Need to refill storage Dewar |
| 1335 | Fill LN2 cold trap bath |
| 1335 | Baselines for DCRC1pA/B/C/DCRC3pA/B/C = -0.783/-0.783/-0.780/-0.779/-0.785/-0.778 V |
| Baselines are clearly elevated so it looks like the He films are now affecting the phonon channels (some time in the last hour and a half). Also seeing a lot of wiggles in the baseline that are likely He-film induced (like at Soudan). This would explain why in recent cycles when we're taking data the dump sizes start to increase and vary a lot when the phonon channels go bad - these wiggles increase the trigger rate. | |
| Confusingly the phonon channels went bad about 45 hours after we cooled to base, even though this was a standard cooldown, which usually gives us something closer to 55 hours. This is more similar to the recent tests where let the IVC sit for a day after we stopped pumping on it, before cooling. | |
| Between 9:30 and 10:30 the MC baseline temperature rose from 29.6 mK to peak around 30.6 mK, then came down somewhat. About two hours after that rise-and-fall ended the phonon channel symptoms began. | |
| 1345 | Close V6 to stop circulation. |
| 1345 | Stop DAQ programs and unplug DCRCs 1&3 |
| 1355 | V6 is now fully closed (light is off on IGH, Still pressure is rising, Condenser pressure falling). Turn off 3He pump |
| 1355 | Open V3 to let mixture from Condenser side into Still side. |
| 1355 | Close 1K Pot needle valve |
| 1400 | MC = 0.49 K |
| 1400 | Turn on Still and MC heaters to 20 mW each |
| 1425 | MC = 2.46 K. 1K Pot = 1.51 K. |
| 1425 | Close 1K Pot speedivalve, V4a, 4He pump inlet valve. Turn off 4He pump. Close recovery valve to 4He pump outlet. NOTE: remember to open recovery valve when the pump is turned back on. |
| 1515 | MC/1KPot = 3.82/4.07 K. G1(fridge) = 802 mbar. |
| 1515 | Open V9 to release pressure into the dump. |
| 1555 | MB = 35.9% |
| 1615 | MC/1KPot = 6.05/4.36 K, pretty flat |
| 1615 | Check pressure in IVC: 0.086 ubar, strangely low. Start pumping out IVC with turbo pump. |
| 1805 | Tower = 10.01 K. Turn off MC and Still heaters |