2020/03/14 (Saturday)
| Setup | Run 72. DIB 1/3/4 → Stripline 43/41/48 → Cable 3/2/1 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1). DCRCs off overnight. Lead/poly shield erected (4 lead walls, 2 poly walls). |
|---|---|
| Status | Initial LHe transfer yesterday. Second cooldown for Run 72. |
| 1040 | MC(Cernox)/Sorb/1K Pot = 4.54/8.3/6.56 K. G1(fridge) = 550.1 mbar (3He pump on). MB = 63.0% / 188 mbar |
| 1040 | MC(H35)/Tower = 4.55/4.55 K. (Coldplate/Still = 14.6/10.4 K. These clearly don't have good calibrations here.) |
| 1045 | Turbo on IVC = 4.6 nbar. With turbo valved out for a minute, IVC = 74 nbar. Open Turbo valve again, we'll keep pumping on IVC. |
| this is a little worse than last time. | |
| 1050 | Fill LN2 cold trap bath from 5L Dewar. |
| 1050 | 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. |
| 1055 | Check pressure in 1K Pot at P2: P2 goes off scale. Clearly plenty of gas leaked into the 1K Pot, which was pumped out yesterday. Mechanical gauge = 0.23 bar. 1K Pot temperature dips to 4.8 K, then up to 5.5 K, then falls again to 4.1 K. |
| 1105 | 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 4 iterations leave V4a and 1K Pot speedivalve open. 1K Pot → 3.4 K / 1.4 mbar |
| 1110 | MC(H35)/Sorb = 4.52/4.2 K, MC falling. G1 (fridge) = 526 mbar and falling. |
| 1115 | 1K Pot = 3.25 K / 1.3 mbar, MC(H35)/Sorb = 4.50/4.1 K, G1 (fridge) = 516 mbar. All falling except Pot pressure and Sorb. |
| 1120 | Open 1K Pot needle valve → 10°. 1K Pot → 3.0 K / 4.5 mbar. MC and Fridge start falling faster. Open 1K Pot needle valve → 20°. 1K Pot → 2.7 K / 9.5 mbar. MC(H35) = 4.29 K. G1 (fridge) = 471 mbar. MC falls much faster, → 3.38 K. |
| 1125 | Open 1K Pot needle valve → 30°. 1K Pot → 2.4 K / 22 mbar. MC(H35) = 3.28 K. G1 (fridge) = 418 mbar. |
| 1130 | Open 1K Pot needle valve → 40°. 1K Pot → 2.0 K / 40 mbar. MC(H35) = 3.17 K. G1 (fridge) = 370 mbar. |
| 1135 | 1K Pot = 1.82 K / 40 mbar. Already colder than the first Run72 cooldown, good! |
| 1135 | MC(H35) = 2.95 K. G1 (fridge) = 280 mbar. |
| 1140 | 1K Pot = 1.70 K / 40 mbar. MC(H35) = 2.66 K. G1 (fridge) = 185 mbar. |
| 1140 | Open 1K Pot needle valve → 50°. 1K Pot → 1.72 K / 60 mbar. |
| we'll leave it like this for the mixture to condense. Can start circulation remotely. | |
| 1K Pot seems much more healthy than last time - temperature was higher and pressure a lot higher. Also MC is cooling faster than last time. | |
| 1200 | MC hits 2.1 K, lambda point. 1K Pot jumps from 15→~150 mbar and oscillating, 1.6 → 1.75 K |
| 1310 | 1K Pot = 1.74 K / 130±40 mbar. MC(H35) = 1.90 K. G1 (fridge) = 53.5 mbar. |
| 1310 | Close V3 and V9, leaving 27.8 mbar (G2) in the dump. |
| 1315 | Start circulation through Trap 1. V6 → 12.8%. Condenser peaks at 145 mbar. MC falls to 1.58 K. 1K Pot spikes for a moment. |
| 1325 | V6 → 13.2%. Condenser peaks at 110 mbar. 1K Pot spikes and recovers. MC(H35) → 1.58 K |
| 1330 | MC(H35) = 1.57 K, G1/G2 = 111/102 mbar, 1K Pot = 1.73 K / 130±20 mbar. |
| 1330 | V6 → 13.4%. Condenser peaks at 125 mbar. MC(H35) → 1.50 K |
| 1350 | V6 → 13.6%. Condenser peaks at 130 mbar. MC(H35) → 1.37 K. Still → 150 mbar. |
| 1355 | V6 → 14.0%. Condenser peaks at 150 mbar. MC(H35) oscillates between 1.05 and 1.25 K, I guess this is the Al going SC. Still → 6 mbar. |
| MC has interesting sawtooth pattern, quick fall to 1.07 K then slower rise to 1.24 K, 3 cycles with about 2-minute period | |
| 1415 | V6 → 14.4%. Condenser peaks at 140 mbar. MC(H35) → 0.83 K. Still → 4 mbar. |
| 1430 | V6 → 15.0%. Condenser peaks at 135 mbar. MC(H35) → 0.48 K. Still → 2.2 mbar. |
| 1450 | MC(H35) = 0.28 K. Condenser = 109 mbar and falling. Still = 1.4 mbar. |
| 1450 | V6 → 100%. Condenser peaks at 120 mbar. MC(H35) → 0.20 K, falling fast. Still → 0.26 mbar. |
| 1500 | MC(H35) = 76 mK, Still = 0.180 mbar, G1/G2 = 100/89 mbar, 1K Pot = 1.73 K / 120±20 mbar. |
| 1520 | MC(H35) reaches 37.5 mK and flatlines. Probably I did not set the resistance range high enough on the LakeShore bridge. (Working remotely.) |
| 1520 | Open V14 to let the remaining mix out of the dump and into circulation. P1(Still) peaks at 150 mbar then falls again. Condenser peaks at 110 mbar. MC(H35) peaks at 85 mK then falls again. 1K Pot pressure reacts briefly. |
| As MC cools again, there's a bounce from 84 mK to 90 mK, then it cools again. Is this the phonon channels going s/c? | |
| 1545 | MC(H35) flatlines ate 37.5 mK again. |
| 1550 | Still = 0.7 mbar |
| 1550 | Close V14 |
| 1605 | MC(H35) = <38 mK, Still = 0.140 mbar, G1/G2 = 77/64 mbar, 1K Pot = 1.73 K / 125±15 mbar. |
| 1850 | Hongguang reset the LakeShore range to 200 kOhm. Now the MC thermometer is no longer pegged. But the temperature is strangely unstable. |
| 1855 | MC(H35) is on a random walk, rising and falling, 39±2 mK. Still, circulation, 1K Pot are perfectly stable. Maybe it's just a thermometry problem? |
| …or more likely - there's helium in the IVC. which would have occurred on Friday the 13th, natch. |