2018/05/04 (Friday)
| LN2 transfer last night, cooling to 77 K overnight. | |
| 0933 | MC(Cernox) = 77.4 K, G1 (fridge) = 207 mbar, IVC = 1.6 mbar, Old Level resistor = 1.209 kΩ, New level resistor = 2.979 kΩ |
| 0940 | Start pumping out IVC with scroll pump, then turbo pump |
| 0945 | Electrical check on DIB3, all OK except SQUID A open (which we knew about) |
| 0950 | Electrical check on DIB1, all OK |
| 0955 | Electrical check on DIB4, all OK. A short to ground somewhere in QI between FET and feedback line. |
| 1040 | Turbo on IVC = 4 nbar; IVC with turbo valved out = 74 nbar; leak on IVC = 220 pbarL/s with turbo pumping, 1500 pbarL/s with turbo valved out |
| 1130 | Turbo on IVC = 4 nbar; leak on IVC > 1000 pbarL/s with turbo valved out |
| 1200 | Leak on IVC = 1250 pbarL/s with turbo valved out |
| 1205 | Start blowing out LN2 |
| 1205 | IVC leak = 1230 pbarL/s, Main bath = 385 mbar above 1 atm, New level resistor = 2.978 kΩ |
| 1210 | IVC leak = 1190 pbarL/s, Main bath = 408 mbar above 1 atm, New level resistor = 2.980 kΩ |
| 1215 | IVC leak = 1150 pbarL/s, Main bath = 404 mbar above 1 atm, New level resistor = 2.980 kΩ |
| 1220 | IVC leak = 1100 pbarL/s, Main bath = 404 mbar above 1 atm, New level resistor = 2.974 kΩ |
| 1225 | IVC leak = 1070 pbarL/s, Main bath = 397 mbar above 1 atm, New level resistor = 2.971 kΩ |
| 1230 | IVC leak = 1050 pbarL/s, Main bath = 160 mbar above 1 atm, New level resistor = 2.974 kΩ |
| 1231 | Main bath = 124 mbar above 1 atm. Stop pressurizing main bath. |
| 1235 | IVC leak = 1040 pbarL/s, New level resistor = 2.960 kΩ |
| 1240 | Try Mini-throughput check: close off Trap 1 and V3. Only V1, condenser speedivalve, still gate valve open. Turn on 3He pump, then open V6 to 12.4%. This pumps mix out of the still side and we can see if the pressure goes down on the condenser side. G1 (condenser) started out at 200 mbar, starts to fall slowly. Realized that 12.4% is low, Still pressure is not dropping - increase V6→ 13.5%. Still pressure falls, condenser falls more rapidly, about 5.5 mbar/min |
| 1245 | IVC leak = 987 pbarL/s, New level resistor = 2.947 kΩ |
| 1250 | Start pumping main bath with scroll pump. |
| 1245 | IVC leak = 968 pbarL/s, New level resistor = 2.953 kΩ |
| 1300 | Main bath = 0.75 mbar, looks like all the LN2 is out. |
| 1300 | IVC leak = 956 pbarL/s, New level resistor = 2.953 kΩ |
| 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
| 1300 | Perform mixture throughput test at MC = 77 K using above procedure. Let G1 rise to 585 mbar before Step 3, then it falls to 82 mbar, then begins to rise. Throughput 45.2 mbar/min. Close to May 1. |
|---|---|
| 1310 | Check pressure in 1K Pot: 40 mbar. Pump out with scroll pump. (After pumping it out, leave 1K Pot speedivalve open, to pressurize it with He along with the main bath.) |
| 1315 | Pressurize MB and 1K Pot with helium to 190 mbar above 1 atm. Close 1K Pot speedivalve. |
| 1320 | IVC leak = 906 pbarL/s, New level resistor = 2.929 kΩ |
| 1325 | Let 63 μbar He exchange gas into IVC. |
| 1330 | Open dump to cold LN2 Trap 1 and both sides of fridge. Turn off 3He pump. |
| 1330 | MC(Cernox) = 77.4 K, Sorb = 133.4 K, IVC = 63 μbar, G1(fridge) = 598 mbar. |
| 1350 | Begin initial LHe transfer |
| 1350 | MC(Cernox) = 77.6 K, Sorb = 137.5 K, IVC = 63 μbar, G1(fridge) = 598 mbar. New level resistor = 2.90 kΩ |
| 1400 | MC(Cernox) = 77.7 K, Sorb = 137.6 K, IVC = 63 μbar, G1(fridge) = 596 mbar. New level resistor = 3.17 kΩ |
| 1430 | MC(Cernox) = 75.5 K, Sorb = 105.2 K, IVC = 30 μbar, G1(fridge) = 565 mbar. New level resistor = 61.1 kΩ |
| 1510 | main bath pressure started to rise, according to LabVIEW vi. Had been steady at 310 mbar above 1 atm. |
| 1520 | main bath pressure off-scale on G3, i.e. >1 bar above 1 atm, I guess around 15 PSI. At this time the pictures that the computer was taking of the level meter become blurry. |
| 1525 | left to go see the MXP poster session, and came back to see that the 250L LHe Dewar had blown its top. The vacuum must have failed. The MB was at very high pressure and the recovery meter was oscillating wildly. We stopped pressurizing it, and opened the release valve but nothing is coming out. I pulled the stopper out of the third fridge port to release the pressure. I think the recovery meter may be broken. |
| 1535 | Now that the stopper has been removed from the main bath the Dewar is settling down. Now there actually is gas coming out of the Dewar's release valve. |
|---|---|
| 1535 | Transfer has ended, of course |
| 1545 | MC(Cernox) = 57.1 K, Sorb = 12.5 K, IVC = 1.2 μbar, G1(fridge) = 560 mbar. New level resistor = OL(?) kΩ, Main bath = 14.6% |
| 1600 | Weighed Dewar, found that all LHe was boiled off. Clearly the Dewar vacuum failed. |
| 1610 | Start another LHe transfer @ MB = 10.8%. Using a new 100L Dewar. |
| Recovery meter seems to be working normally. Maybe it just froze up temporarily. | |
| 1625 | MC(Cernox) = 47.7 K, Sorb = 7.2 K, IVC = 0.19 μbar, G1(fridge) = 489 mbar. New level resistor = 71.3 kΩ, Main bath = 32.2% |
| MC temperature is not very low, but IVC pressure is much lower than usual. Hrm. Well, we'll have all weekend to pump it out at 4K, hopefully it will be ok. Don't want to pump out too early while the MC is still so warm. | |
| 1635 | MC(Cernox) = 43.9 K, Sorb = 6.9 K, IVC = 0.16 μbar, G1(fridge) = 458 mbar. New level resistor = 71.1 kΩ, Main bath = 51.5% |
| 1645 | MC(Cernox) = 42.5 K, Sorb = 6.9 K, IVC = 0.16 μbar, G1(fridge) = 457 mbar. New level resistor = 71.3 kΩ, Main bath = 58.4% |
| 1655 | MC(Cernox) = 39.3 K, Sorb = 6.8 K, IVC = 0.16 μbar, G1(fridge) = 455 mbar. New level resistor = 71.4 kΩ, Main bath = 69.9% |
| 1710 | MC(Cernox) = 34.7 K, Sorb = 6.6 K, IVC = 0.16 μbar, G1(fridge) = 453 mbar. New level resistor = 71.4 kΩ, Main bath = 86.7% |
| 1715 | End LHe transfer @ MB = 88.2% |
| 1725 | MC(Cernox)/Sorb/1K Pot = 29.4/6.3/5.0 K. IVC = 0.16 μbar, G1(fridge) = 503 mbar. New level resistor = 74.6 kΩ |
| 1730 | Fill LN2 cold trap bath |
| 1740 | MC(Cernox)/Sorb/1K Pot = 22.7/6.1/4.9 K. IVC = 0.16 μbar, G1(fridge) = 505 mbar. New level resistor = 74.7 kΩ |
| 1755 | MC(Cernox)/Sorb/1K Pot = 13.9/5.8/4.6 K. IVC = 0.14 μbar |
| 1755 | Start pumping out IVC with turbo pump |