2018/06/27 (Wednesday)
| Setup: DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2 → gender changer 3/?/2 → HVConn 1/3/2 → HV 1/2 → DCRC55(1)/DCRC50(3) | |
| overnight: DCRCs on. Tower temperature relatively stable. It plateaued around 45 mK for a few hours, then fell to about 44 mK and settled. | |
| 0935 | Tower/MC/Coldplate = 44.1/41.8/190 mK, Still = 1.26 K / 0.050 mbar / 0.5 mW, G1/G2 = 258/241 mbar, 1K Pot = 1.45 K / 4.0 mbar. MB = 43.0% |
| 0940 | Fill LN2 cold trap bath |
| 1015 | Tower has risen a little since the LN2 fill (which reduced the circulation pressures as usual). Increase Still heat from 0.5 to 2.0 mW |
| 1040 | Increasing still heat caused significant cooling, Tower → 37.4 mK. Then it began to rise again. Meanwhile circulation pressures rose as well, → 322/300 mbar. |
| 1040 | Reduce Still heat 2.0→1.0 mW. Doesn't stop the warming trend. Increase Still heat →3.0 mW. |
| 1045 | Tower temperature continues to rise, now 45.0 mK, higher than when I first increased the still heat 30 minutes ago |
| 1050 | Tower = 51.3 mK and still rising steadily. G1/G2 = 354/329 mbar and rising. Turn off Still heat → 0.0 mW |
| 1055 | Tower = 60.2 mK and rising. G1/G2 are now falling. Turn on Still heat → 1.0 mW |
| 1100 | Tower = 68.9 mK and rising. G1/G2 flat at 342/318 mbar. |
| this sudden unprovoked temperature increase, occurring after a decrease in temperature, feels a bit like helium in the IVC. It gets cold enough that a superfluid temperature bridge forms (or something) then there's a runaway temperature increase. (Though I might expect a stronger increase than what we are seeing.) | |
| 1115 | Tower seems to have peaked at 75 mK |
| 1135 | Tower cooling slowly, now 73.5 mK |
| 1135 | Turbo = 3 nbar, pumping on IVC. Close turbo valve. IVC = 22 nbar. |
| 1140 | Switch to one-shot mode: close V13a, open V9. G2 (dump) falls to 46.6 mbar, then starts rising. |
| 1240 | Install lead/poly shield. West and East walls installed. North wall poly installed. |
| 1330 | North wall lead installed. South wall not built: currently HPGe detector is there, along with 22Na source, for a test. |
| 1510 | Still in one-shot mode. G2(dump) currently 230 mbar, so we surely have all the 3He by now. Tower currently 0.8 K. Still = 1.54 K. We have pressures and temperatures logged so we can look more closely later and try to guess what the 3He ratio is. (Maybe next time we can log Still temperature instead.) |
| 1515 | IVC = 25 nbar, slightly higher than earlier. |
| 1515 | Close 1K Pot speedivalve to stop pumping on pot. 1K Pot rises quickly from 1.47 K → 2 K. G1 (condenser) pressure rises quickly from 48 mbar → 150 mbar. |
| 1540 | 1K Pot has risen to 2.6 K, G1 (condenser) has risen to 310 mbar and flattening. Tower temperature is flat (0.84 K) and G2 (dump) is still only slowly increasing, now 247 mbar. |
| 1540 | Increase Still heat to 20 mW. After a couple of minutes Dump pressure and Tower temperature start rising quickly. |
| 1545 | Tower peaked at 3K, then fell to 2K. Dump = 333 mbar and rising. IVC 30 nbar. |
| 1550 | Tower fell to 1.2 K, then rose sharply to 2.7 K, and IVC rose to 60 nbar. Tower falls again and IVC pressure falls too. |
| 1607 | Start LHe transfer @ MB = 34.6% |
| 1610 | Tower ~ 2.7 K, Condenser pressure has oscillated, now at 294 mbar and falling Dump continues to rise, now 636 mbar, 1K Pot hwas risen to 4.1 K. Close 1K Pot needle valve IVC = 63 nbar, has been oscillating a bit |
| 1615 | Tower suddenly rises from 2.8 to 4 K as Dump reaches 705 mbar and starts to level out. IVC → 140 nbar. |
| 1625 | Tower flat at 4.4 K. Dump flat at 709 mbar. Condenser (which is also trap pressure) still relatively high, 250 mbar. IVC = 140 nbar. |
| 1625 | Turn on MC heater to 20 mW. MC → 4.7 K, IVC → 160 nbar |
| 1642 | End LHe transfer @ MB = 93.3% |
| 1655 | Tower = 4.67 K and flat, Dump = 714 mbar and flat, condenser/trap1 = 238 mbar and flat. And still = 0.02 mbar - that's a little strange, it seems like a blockage. IVC = 160 nbar. Start pumping out IVC with turbo. |
| 1705 | Close V1 and open V5 to pump Trap 1 to dump |
| 1705 | Fill LN2 cold trap bath |
| 1710 | Trap = 0.6 mbar, flat. Dump = 728.6 mbar. |
| 1715 | Isolate trap, then open V1 (V5 is still open) to pump out condenser side. G1 spikes to 54 mbar then starts to fall, so there was definitely still mixture on the condenser side. Dump rises to 737.5 mbar. |
| 1720 | Close all IGH valves and turn off 3He pump |
| 1720 | Turbo on IVC = 4.6 nbar. Tower = 5.4 K and rising steadily for last 20 minutes. Turn off MC and Still heaters. Tower temperature starts to fall. |
| 1735 | Turbo on IVC = 2.5 nbar, Tower down to 4.7 K. We may not be pumping it out as efficiently with the heater off but hopefully overnight pumping should get out any helium. |
