2019/03/07 (Thursday)
| Status: | Initial LHe transfer yesterday |
|---|---|
| 0905 | MC(Cernox) = 7.1 K, Sorb/1K Pot = 8.6/6.7 K, Turbo on IVC = 3 nbar, G1(fridge) = 560 mbar. MB = 63.0 % |
| Turbo on IVC pressure not as low as last time. | |
| 0910 | Pump out lines leading to 1K Pot with scroll pump |
| 0920 | Start 4He pump, but it doesn't get to a low pressure - only 4.5 mbar. As on 2018 May 7 the oil looks low. Put some Leybonol LVO 100 Mineral Oil in the center spout on top, until the level is up about 20% when the pump is off. Now it pumps down fine. |
| 0935 | Check pressure in 1K Pot: about 0.22 bar on the mechanical gauge. Opening the 1K Pot speedivalve to P2 causes the 1K Pot temperature to fall from 6.7 to 4.9 K. |
| 0940 | Pump out 1K Pot in steps, alternating between V4a and the 1K Pot speedivalve. After 5 iterations get pot down to < 0.1 bar. Then leave 4He pump pumping on pot continuously. |
| 0945 | 1K Pot = 3.4 K / 0.9 mbar MC temperature falls slightly, Fridge pressure falling. |
| 1055 | MC(Cernox) = 4.8 K, Fridge(G1) = 499 mbar. Both falling. |
| 1055 | 1K Pot = 3.1 K / 0.9 mbar, steady. |
| 1100 | Open 1K Pot needle valve → 10°. 1K Pot → 2.9 K / 3.4 mbar After a couple minutes MC starts falling rapidly, 4.5 → 3.4 K. Fridge pressure falling faster too. |
| 1105 | Open 1K Pot needle valve → 20°. 1K Pot → 2.8 K / 4.5 mbar Open 1K Pot needle valve → 30°. 1K Pot → 2.7 K / 6.0 mbar |
| 1110 | MC(Cernox) = 3.33 K, Fridge(G1) = 436 mbar. Both falling. |
| 1110 | Open 1K Pot needle valve → 40°. 1K Pot → 2.5 K / 12 mbar |
| 1115 | Open 1K Pot needle valve → 50°. 1K Pot → 2.2 K / 20 mbar Open 1K Pot needle valve → 60°. 1K Pot → 2.0 K / 40 mbar |
| 1120 | MC(Cernox) = 2.97 K, Fridge(G1) = 286 mbar. Both falling. |
| 1130 | MC(Cernox) = 2.52 K, Fridge(G1) = 140 mbar, 1K Pot = 1.92 K / 22 mbar |
| 1140 | MC(Cernox) = 2.31 K, Fridge(G1) = 91 mbar, 1K Pot = 1.82 K / 11 mbar |
| 1145 | Spontaneous jump in 1K Pot, → 1.85 K / 45 mbar. MC temperature flattens out. |
| 1210 | MC(Cernox) = 2.27 K, Fridge(G1) = 89 mbar, 1K Pot = 1.84 K / 45 mbar MC and Fridge look pretty flat |
| 1245 | MC(Cernox) = 2.28 K, Fridge(G1) = 91 mbar, 1K Pot = 1.84 K / 45 mbar |
| 1250 | Fill LN2 cold trap bath. Fridge pressure falls slightly. |
| 1255 | Close V3 and V9, leaving 70 mbar in the dump. |
| 1255 | Start circulation through Trap 1. V6 → 12.8%. Condenser peaks at 380 mbar. Tower falls to 1.82 K. 1K Pot spikes offscale pressure / 2.22 K, then falls again. |
| 1300 | P1(Still) falls into range. This is kind of early. Hopefully it's not a sign of blockage… (maybe it's just that we've left more mix in the dump this time) |
| P1 fell as low as 30 mbar, then rose somewhat. | |
| 1305 | Tower = 1.39 K, G1/G2 = 129/121 mbar, 1K Pot = 1.87 K / 45 mbar |
| 1305 | V6 → 13.2%. Condenser peaks at 175 mbar. Still rose to around 100 mbar then fell to 50 mbar. Tower = 1.41 K |
| 1315 | V6 → 13.4%. Condenser peaks at 167 mbar. Still → 30 mbar. Tower → 1.36 K |
| 1320 | V6 → 13.6%. Condenser peaks at 172 mbar. Still → 11 mbar. Tower → 1.28 K |
| 1325 | V6 → 14.0%. Condenser peaks at 187 mbar. Still → 5.5 mbar. Tower → 1.20 K |
| 1330 | V6 → 14.4%. Condenser flattens at 179 mbar. Still → 3.6 mbar. Tower → 0.96 K |
| 1340 | V6 → 15.0%. Condenser peaks at 179 mbar. Still → 2.0 mbar. Tower → 0.61 K |
| 1K Pot has been flat at 1.89 K / 45 mbar | |
| 1350 | V6 → 100%. Condenser peaks at 170 mbar. Still → 0.3 mbar. Tower → 0.37 K |
| 1405 | Tower = 95 mK, Still = 0.190 mbar, Condenser = 114 mbar, 1K Pot = 1.88 K / 45 mbar. |
| 1410 | Tower = 79.2 mK, Still = 0.170 mbar, Condenser = 102 mbar, 1K Pot = 1.87 K / 45 mbar. |
| 1415 | Open V14 to let the remaining mix out of the dump and into circulation. P1(Still) rises off scale, falls again after a few minutes. Condenser peaks at 170 mbar. Tower → 115 mK and rising. 1K Pot peaks at 2.0 K / 50 mbar. |
| 1420 | Tower plateauing at 133 mK. P1(Still) = 6 mbar and falling. Condenser = 107 mbar. |
| 1430 | Tower has cooled back to 84.4 mK. P1(Still) = 1.6 mbar and falling. Condenser = 103 mbar. |
| 1445 | P1(Still) = 0.70 mbar. Close V14. |
| 1455 | Tower/MC/Coldplate = 75.0/35.0/200 mK, Still = 1.7±0.1 K / 0.170 mbar, G1/G2 = 101/95 mbar, 1K Pot = 1.87 K / 45 mbar. |
| MC is quite low already, guess it'll take longer to cool the detector. | |
| 1530 | Tower/MC/Coldplate = 72.6/32.9/200 mK, Still = 1.7±0.1 K / 0.170 mbar, G1/G2 = 101/96 mbar, 1K Pot = 1.86 K / 45 mbar. |
| 1600 | Tower/MC/Coldplate = 71.8/32.7/200 mK, Still = 1.75±0.05 K / 0.170 mbar, G1/G2 = 101/96 mbar, 1K Pot = 1.86 K / 45 mbar. |
| 1630 | Tower = 71.2 mK, Still = 0.170 mbar, G1/G2 = 101/96 mbar, 1K Pot = 1.86 K / 45 mbar. |
| 1645 | Fill LN2 cold trap bath |
| 1702 | MB = 50.4% |
| There's pretty clear indication that the Still and Cold Plate temperatures are higher this run than recent runs. In this run we left off the 4K shield and heat sinks. I had thought that the heat sinks from the IVC to the 4K tower stage might be sending more heat into the tower. But the higher temperatures suggest the opposite, that the heat sinks were taking heat away from the tower, heat originating from conduction through the striplines (suggesting the 4K heatsinking of the striplines is not terribly efficient). So removing this heatsinking is probably sending more heat into the 4K tower stage, heat that is then taken away via conduction through the carbon tubes to the 600mK stage and up through the 600mK rod to the still, and also to the cold plate. |