2017/09/21 (Thursday)
| Status: LN2 transfer yesterday. Cooled with mixture in fridge and open to Cold Trap 1. | |
| 0905 | MC(Cernox) = 93.2 K, Sorb = 167.4 K, IVC = 1.9 mbar, G1 (fridge) = 644 mbar. Temperatures have been steadily increasing overnight. |
| 0910 | Begin pumping exchange gas out of IVC |
| 0925 | Start pumping IVC with leak detector. We haven't been pumping out the IVC very long so there's still a significant amount of He in there. LD signal rises to 1400 pbarL/s (1.4 e-6 mbarL/s). We'll monitor it regardless during LN2 blowout. |
| 0930 | Begin blowing out LN2. G3 close to 400 mbar - close helium cylinder regulator valve a bit to reduce this to around 300 mbar. |
| 0935 | G3 is already starting to fall quickly, and doesn't look like much liquid is coming out of tube. Probably already about empty. |
| 0935 | LD signal has not increased, rather has fallen to 1100 pbarL/s. |
| 0945 | Begin pumping out MB with scroll pump. |
| 0955 | P2 has fallen below 1 mbar: MB is empty. |
| 1000 | Fill MB with helium gas, to 90 mbar on G3. |
| 1010 | Mini-throughput check: close off Trap 1 and V3. Only V1, condenser speedivalve, still gate valve, and V9 open. Turn on 3He pump, then open V6 to 12.8%. This pumps mix out of the still side and we can see if the pressure goes down on the condenser side. P1 (still) falls to 0.3 mbar after a few minutes. G1 (condenser) falls, from 640 mbar to 520 mbar in 4 minutes, and continues to fall. Good, looks like we have throughput. |
| 1015 | LD has been falling steadily, no increases. Currently 690 pbarL/s. |
| 1020 | Let 63 μbar He exchange gas into IVC. |
| 1030 | Pump out 1K Pot with scroll pump |
| 1045 | Begin initial LHe transfer |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 traps cold, condenser & still valves open (3He pump on - optional)
- Open V9, V13a, V12a+speedivalve, V3. Wait for G1 to be close to G2.
- Close V12a+speedivalve and V3, open V1
- monitor G1
| 1100 | Perform mixture throughput test at MC = 92.5 K using above procedure. Let G1 rise to 600 mbar before Step 3, then it falls to 63 mbar and begins to rise. Throughput: 30.3 mbar/min. A little lower than Run 63 but that's expected since we're warmer than 77K. |
|---|---|
| 1105 | MC(Cernox) = 92.7 K, Sorb = 171.7 K, IVC = 54 μbar. MC and Sorb are just beginning to fall. |
| 1110 | Open both sides of fridge to Trap 1 and Trap 1 to dump. 3He pump is off. |
| 1130 | MC(Cernox) = 92.0 K, Sorb = 165.5 K, IVC = 0.19 μbar, G1(Fridge) = 637 mbar. |
| The IVC pressure dropped a lot, like it did before Run 63. But at that time we attributed it to air having leaked into the IVC during the period between the two different LN2 transfers. No explanation why it happened this time. Like last time, let some He back in. | |
| 1200 | Put 25 μbar He into IVC. Why did it go down so much??? |
| 1200 | MC(Cernox) = 82.9 K, Sorb = 111.1 K, IVC = 25 μbar, G1(Fridge) = 621 mbar. |
| 1210 | Copper coil for warming recovery gas is partly frosty, partly not. That's good. |
 |  |  |
| 11:12 | 12:52 | Temperature measurements near end of coil |
| 1230 | MC(Cernox) = 58.5 K, Sorb = 34.1 K, IVC = 16 μbar, G1(Fridge) = 564 mbar. |
|---|---|
| 1300 | MC(Cernox) = 40.1 K, Sorb = 6.1 K, 1K Pot = 4.8 K, IVC = 12 μbar, G1(Fridge) = 512 mbar. |
| 1330 | MC(Cernox) = 19.8 K, Sorb = 5.5 K, 1K Pot = 4.31 K, IVC = 74 μbar, G1(Fridge) = 483 mbar. MB level meter still at minimum, -1.0% |
| why did IVC pressure increase??? | |
| 1335 | As soon as MC hits 10 K, start pumping out IVC with turbo pump. Temperature falling rapidly at this time. IVC had crept up to 86 μbar. |
| 1340 | MC(Cernox) = 4.24 K, Sorb = 5.3 K, 1K Pot = 4.18 K, G1(Fridge) = 482 mbar. MB = -1.0% (min) |
| 1345 | MB = 8.2% |
| 1400 | MC(Cernox) = 4.23 K, Sorb = 5.3 K, 1K Pot = 4.17 K, G1(Fridge) = 474 mbar. MB = 25.2% |
| 1400 | Turbo = 0.25 μbar, IVC = 19 μbar |
| 1420 | MC(Tower)/Sorb/1K Pot = 4.28/5.3/4.16 K, Fridge(G1) = 471 mbar, MB = 49.1%. |
| 1430 | MC(Tower)/Sorb/1K Pot = 4.28/5.3/4.18 K, Fridge(G1) = 472 mbar, MB = 58.6%. |
| 1440 | MC(Tower)/Sorb/1K Pot = 4.28/5.3/4.17 K, Fridge(G1) = 469 mbar, MB = 67.8%. |
| 1450 | MC(Tower)/Sorb/1K Pot = 4.28/5.3/4.17 K, Fridge(G1) = 468 mbar, MB = 76.7%. |
| 1500 | MC(Tower)/Sorb/1K Pot = 4.28/5.3/4.21 K, Fridge(G1) = 467 mbar, MB = 85.9%. |
| 1511 | End transfer @ 90.3% |
| 1530 | MC(Tower)/Sorb/1K Pot = 4.27/5.8/4.55 K, Fridge(G1) = 549 mbar |
| 1600 | Something went wrong with the 250L Dewar. Allison was the only one in the lab at the time. It apparently lost its vacuum. It had 111 L left in it after the transfer. It's overpressure valve opened up. Allison tried various pressure releases, opening different things at the top. Eventually it calmed down - presumably it has boiled off most of its LHe. |
| 1700 | Take 250L Dewar back to Bill Voje's recovery manifold. It had 111 L in it after the transfer, now it has 3 L. |
| 1730 | MC(Tower)/Sorb/1K Pot = 4.34/5.9/4.64 K, Fridge(G1) = 568 mbar, MB = 90.0%. |
| 1730 | Turbo = 12 nbar, IVC = 140 nbar |
| 1740 | Fill LN2 cold trap bath |