2020/08/20 (Thursday)
- Lab in-person: Matt
- Virtual partner: Michael, Zach
| 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 off overnight. Lead/poly shield erected (4 lead walls, 2 poly walls). |
|---|---|
| Status: Added more 4He to the mixture three days ago, fridge couldn't cool below 0.4 K. Yesterday boiled off bath and warmed fridge to 12 K to pump out helium from IVC, then transferred LHe. Will try 1K Pot and circulation today. | |
| 0835 | Matt Fritts body temperature 97.7 °F |
| 0900 | Matt enters lab |
| 0915 | MC(Cernox)/Sorb/1K Pot = 5.2/7.5/5.9 K, Turbo on IVC = 4.0 nbar, G1(fridge) = 575 mbar (3He pump on). G3(MB) = 136 mbar+1atm. |
| 1010 | Pump out line leading to 1K Pot Speedivalve using 4He pump. |
| 1015 | Check pressure in 1K Pot: 12/30 = 0.4 atm on mechanical gauge. 1K Pot temperature dips to 3.6 K. |
| 1025 | Pump out 1K Pot in steps, alternating between V4a and the 1K Pot speedivalve, opening V4a for short bursts to keep P2 below about 10 mbar. After several iterations leave V4a and 1K Pot speedivalve open. 1K Pot → 3.3 K / 3.2 mbar |
| 1030 | MC(H35)/Tower = 5.16/5.12 K. Sorb = 4.1 K. G1(Fridge) = 507 mbar and falling. |
| 1035 | MC(H35) falls quickly to 3.5 K then settles. |
| 1035 | Open 1K Pot needle valve → 10°. 1K Pot → 3.1 K / 4.0 mbar. |
| 1040 | Open 1K Pot needle valve → 20°. 1K Pot → 2.8 K / 8.0 mbar. MC(H35) = 3.41 K, G1(fridge) = 450 mbar, falling faster. Open 1K Pot needle valve → 30°. 1K Pot → 2.4 K / 16.0 mbar. |
| 1045 | Open 1K Pot needle valve → 40°. 1K Pot → 2.0 K / 30.0 mbar, with some oscillations. MC(H35) = 3.19 K, G1(fridge) = 347 mbar. Sorb = 4.0 K. |
| 1055 | Fill LN2 cold trap bath |
| 1112 | Begin LHe transfer @ MB = 67.2% |
| 1115 | 1K Pot pressure has dropped a lot. 1K Pot = 1.53 K, 7.5 mbar. Open 1K Pot needle valve → 50°. 1K Pot → 1.57 K / 12.0 mbar. MC(H35) = 2.13 K, G1(fridge) = 62 mbar. |
| 1120 | Open 1K Pot needle valve → 60°. 1K Pot pressure increases slowly, then shoots off scale, then falls again. This happened last time too at about the same MC temperature - close to the lambda point for superfluid He transition. MC(H35) = 2.12 K |
| 1130 | 1K Pot = 1.74 K / 450±50 mbar. Close needle valve → 50°. |
| 1131 | End LHe transfer @ MB = 92.3% |
| 1155 | 1K Pot = 1.69 K / 57±2 mbar. MC(H35) = 2.09 K, cooling very slowly. G1(Fridge) = 56 mbar, was flat but now falling. |
| 1205 | Matt leaves lab |
| 1230 | MC(H35) suddenly drops, 2.08→1.97 K, then starts cooling steadily. G1(Fridge) suddenly rises at the same time, 48.5→51.5 mbar, then starts falling at same rate as before. |
| 1245 | 1K Pot = 1.69 K / 60±2 mbar. MC(H35) = 1.88 K, G1 (fridge) = 49 mbar. |
| 1245 | Close V3 and V9, leaving 48 mbar (G2) in the dump. 3He pump is on. |
| 1250 | Start circulation through Trap 1. V6 → 12.8%. Condenser peaks at 122 mbar. MC falls to 1.68 K. 1K Pot pressure spikes for a moment. |
| Note that G2 peaks higher than G1, that's unusual. Is the LN2 Trap clogged from dirty mixture? | |
| 1255 | V6 → 13.2%. Condenser peaks at 117 mbar. MC(H35) → 1.61 K |
| 1303 | V6 → 13.4%. Condenser peaks at 120 mbar. MC(H35) → 1.53 K |
| 1310 | V6 → 13.6%. Condenser peaks at 128 mbar. MC(H35) → 1.49 K. Still → 100 mbar. |
| 1315 | V6 → 14.0%. Condenser peaks at 145 mbar. MC(H35) → 1.28 K. Still → 9 mbar. |
| 1320 | MC falls to 1.13 K then starts rising, Still and Condenser pressures rise too, looks like we're pushing into the Al Tc. MC peaks at 1.21 K then falls. |
| 1320 | V6 → 14.4%. Condenser peaks at 130 mbar. MC(H35) → 1.05 K. Still → 4.0 mbar. |
| 1325 | MC changed slope a few times but never rose again, now 0.91 K. Sorta looks like now that we have more mixture it has more cooling power, pushes fridge below the Al Tc more easily. |
| 1330 | V6 → 15.0%. Condenser peaks at 147 mbar. MC(H35) → 0.72 K. Still → 2.2 mbar. |
| 1340 | V6 → 100%. Condenser peaks at 145 mbar. MC(H35) → 0.20 K. Still → 0.240 mbar. |
| 1350 | MC(H35) = 57 mK, Still = 0.130 mbar, G1/G2 = 106/116 mbar. Looking good! MC continues to cool. |
| 1405 | MC(H35) = 41.6 mK, Still = 0.095 mbar, G1/G2 = 89/99 mbar. |
| 1420 | MC(H35) = 32.8 mK, Still = 0.095 mbar, G1/G2 = 94/102 mbar. |
| 1420 | Open V14 to let the remaining mix out of the dump and into circulation. P1(Still) peaks at 50 mbar then falls again. Condenser peaks at 140 mbar. MC(H35) peaks at 80 mK. 1K Pot pressure reacts very slightly. |
| 1445 | MC(H35) = 33.4 mK, Still = 0.75 mbar, G1/G2 = 98/105 mbar. |
| 1445 | Close V14 |
| 1455 | MC(H35) = 29.8 mK, Still = 0.110 mbar, G1/G2 = 99/106 mbar. |
| 1540 | MC(H35) = 28.8 mK, Still = 0.095 mbar, G1/G2 = 102/109 mbar. 1K Pot = 1.70 K / 55±2 mbar |
| MC is cooler than it was the first time we cooled down, that's nice. Seems to have flattened out. Let's try heating the still, for fun. | |
| 1540 | Turn on Still Heater to 5 mW. G1/G2 rise to 126/134 mbar, Still rises to 0.16 mbar. MC spikes to 31.5 mK, then falls to 29.0 mK, then starts to rise. |
| 1555 | MC peaks at 29.5 mK then starts coming down again. Let's see what happens. |
| 1655 | MC has settled at 29.0 mK, a little warmer than before the Still heater. |
| 1655 | Turn off Still Heater. MC dips all the way down to 27.6 mK but then rises to 28.6 mK, looks like it's settling. |
| 1725 | MC(H35) = 28.6 mK, Still = 0.095 mbar, G1/G2 = 111/116 mbar. |
| 1750 | MC(H35) = 28.8 mK, Still = 0.095 mbar, G1/G2 = 112/117 mbar. Looks like it's back to where it was before trying the Still Heater. |