2020/07/18 (Saturday)
- Lab in-person: Matt
- Virtual partner: Derek
| 0920 | Matt Fritts body temperature = 97.2 F |
|---|---|
| Status | Initial LHe transfer yesterday. Beginning Run 73 cooldown. |
| 0925 | MC(Cernox)/Sorb/1K Pot = 5.20/8.5/6.65 K. G1(fridge) = 533.6 mbar (3He pump off). |
| 1000 | MB = 64.3% / 115 mbar+1atm |
| 1035 | Matt arrives in lab |
| 1040 | Turbo on IVC = 2.2 nbar. With turbo valved out for several minutes, IVC = 30 nbar. Open Turbo valve again, we'll keep pumping on IVC. this is better than last time. |
| 1045 | Pump out line leading to 1K Pot with scroll pump. Then switch over to 4He pump. Turn on 4He pump then change pump exhaust to recovery and open valve to recovery lines. |
| 1050 | Check pressure in 1K Pot: Mechanical gauge = 0.24 bar. Clearly plenty of gas leaked into the 1K Pot, which was pumped out yesterday. . 1K Pot temperature dips to 4.8 K, then up to 5.5 K, then falls again to 5.0 K. |
| 1100 | Pump out 1K Pot in steps, alternating between V4a and the 1K Pot speedivalve, opening V4a for short bursts only when the mechanical gauge read above a few inches. After 5 iterations leave V4a and 1K Pot speedivalve open. 1K Pot → 3.4 K / 1.2 mbar |
| 1100 | MC(H35)/Tower = 6.18/5.20 K. (Coldplate/Still = 19.4/5.9 K. These don't have good calibrations here. Still lower than expected.) |
| 1105 | MC(H35)/Sorb = 6.2/4.1 K. G1 (fridge) = 512 mbar and falling. MC is falling a little but only slowly. |
| 1110 | Open 1K Pot needle valve → 10°. 1K Pot → 3.0 K / 4.0 mbar. Fridge pressure starts falling faster. Open 1K Pot needle valve → 20°. 1K Pot → 2.8 K / 6.5 mbar. MC(H35) = 6.0 K. G1 (fridge) = 465 mbar. |
| 1115 | Open 1K Pot needle valve → 30°. 1K Pot → 2.4 K / 18 mbar. MC starts falling rapidly. MC(H35) = 3.81 K. G1 (fridge) = 432 mbar. |
| 1120 | Open 1K Pot needle valve → 40°. 1K Pot → 2.0 K / 40 mbar. MC(H35) = 3.66 K. G1 (fridge) = 390 mbar. |
| 1125 | Fill LN2 cold trap bath |
| 1130 | 1K Pot = 1.75 K / 40 mbar. MC(H35) = 3.13 K, G1 (fridge) = 239 mbar, both falling. |
| 1130 | Increase LakeShore Bridge resistance range to 200 kΩ. This caused a temporary excursion in the readout… readout is less stable. Let's try Autorange, see if it works. LakeShore resets the range to 6.32kΩ for now. |
| 1140 | 1K Pot = 1.65 K / 24 mbar. MC(H35) = 2.49 K, G1 (fridge) = 97 mbar, both falling. |
| 1140 | Open 1K Pot needle valve → 50°. 1K Pot → 1.65 K / 26 mbar. Pressure still kind of low. Open 1K Pot needle valve → 60°. 1K Pot → 1.66 K / 32 mbar. |
| 1K Pot pressure still sorta low, but I guess I'll leave it here. Later can start circulation remotely. | |
| 1150 | 1K Pot pressure suddenly shoots up off scale. Perhaps 50 mbar according to the mechanical gauge. (note that above 30 mbar the usual P2 gauge is probably not actually accurate.) 1K Pot temperature → 1.8 K and MC temp, Fridge pressure flatten out. |
| 1155 | Reduce 1K Pot needle valve → 50°. 1K Pot → 1.78 K, pressure falls briefly to 300 mbar on P2 but then climbs off scale again. |
| 1200 | Reduce 1K Pot needle valve → 40°. 1K Pot → 1.70 K / 80 mbar |
| 1205 | 1K Pot = 1.72 K / 80±15 mbar. MC(H35) = 2.28 K, G1 (fridge) = 63 mbar, both flat. |
| 1210 | Matt leaves lab. |
| 1255 | 1K Pot = 1.72 K / 75±15 mbar. MC(H35) = 2.09 K, G1 (fridge) = 55 mbar. |
| 1255 | Close V3 and V9, leaving 57 mbar (G2) in the dump. Turn on 3He pump. |
| 1300 | Start circulation through Trap 2. V6 → 12.8%. Condenser peaks at 85 mbar. MC falls to 2.0 K. 1K Pot pressure spikes for a moment. |
| 1310 | V6 → 13.2%. Condenser peaks at 70 mbar. MC(H35) → 1.92 K |
| 1315 | V6 → 13.4%. Condenser peaks at 75 mbar. MC(H35) → 1.87 K |
| 1320 | V6 → 13.6%. Condenser peaks at 85 mbar. MC(H35) → 1.80 K |
| 1325 | V6 → 14.0%. Condenser peaks at 102 mbar. 1K Pot pressure spikes briefly. MC(H35) → 1.69 K |
| 1335 | V6 → 14.4%. Condenser peaks at 102 mbar. 1K Pot pressure briefly spikes again. MC(H35) → 1.58 K |
| 1345 | V6 → 15.0%. Condenser peaks at 115 mbar. 1K Pot pressure briefly spikes again. MC(H35) → 1.51 K |
| 1355 | V6 → 100%. Condenser peaks at 150 mbar. 1K Pot pressure briefly spikes again. MC(H35) → 1.27 K |
| Just noticed that since turning on the 3He pump, G2 has been much higher than G1. That's very abnormal. Does Trap 2 have a lot of contamination? | |
| 1400 | G1/G2 = 110/261 mbar |
| 1410 | MC climbed upwards slowly from 1.25→1.38 K, then suddenly plummeted to 1.14 K, climbing again. Again maybe this is the aluminum electrode going s/c. |
| 1420 | MC is continuing in a sawtooth, climbing from 1.2→1.36 K over a few minutes then falling rapidly back to 1.2 K. Four cycles so far. |
| 1435 | Sawtooth went through 5 cycles and now the MC seems stuck around 1.25 K, that's not great. Circulation pressures slowly rising. Oh wait - another sawtooth cycle occurs. |
| Also noteworthy: Still (P1) has not yet fallen into readable range | |
| Crap! Just noticed V3 is open! How long has that been open? Surprised the fridge is working as well as it is. | |
| 1440 | Close V3. |
| OK! Suddenly Still pressure falls, G2 falls, and MC temperature falling rapidly | |
| 1445 | MC(H35) = 0.57 K, Still = 0.320 mbar, G1/G2 = 120/136 mbar, 1K Pot = 1.71 K / 65±15 mbar. MC falling steadily. |
| 1500 | MC(H35) = 59.4 mK, Still = 0.170 mbar, G1/G2 = 95/110 mbar. |
| 1500 | Open V14 to let the remaining mix out of the dump and into circulation. P1(Still) peaks at 180 mbar then falls again. Condenser peaks at 118 mbar. MC(H35) rises to 105 mK. 1K Pot pressure reacts briefly. |
| 1525 | MC(H35) = 40.9 mK, Still = 0.850 mbar, G1/G2 = 77/92 mbar. |
| 1530 | Close V14 with Still = 0.65 mbar |
| 1600 | MC(H35) = 32.6 mK, Still = 0.130 mbar, G1/G2 = 77/91 mbar. |
| looks pretty good. And looks like AutoRange works on the LakeShore bridge. | |
| 1900 | MC(H35) = 32.2 mK |
| 1930 | MC rises to 32.4 over a couple minutes, then back down over about 10 minutes. Hopefully this is not a first hint of instability. |