| 1300 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 530 mbar before Step 3, then it falls to 66 mbar, then rises. Throughput = 40.7 mbar/min. A little lower than last time, 2021 Apr 16 |
| 1305 | Open mixture to both sides of the fridge and cold LN2 Trap 1. |
| 1310 | Try Leak Detector on IVC, with Turbo still pumping in parallel. (We've only been pumping out the helium for 30 minutes.) LD = 81 pbarL/s. With Turbo valved out for a minute, LD → 1070 pbarL/s. Open Turbo valve to continue pumping IVC. |
| 1335 | Leak on IVC with Turbo valved out for 1 minute → 815 pbarL/s. Go back to pumping with Turbo |
| 1405 | Leak on IVC with Turbo valved out for 1 minute → 700 pbarL/s. |
| 1410 | IVC = 750 pbarL/s |
| 1410 | Begin blowing out LN2. Main bath (G3) → 575 mbar+1atm |
| 1420 | IVC = 638 pbarL/s, MB = 543 mbar+1atm |
| 1430 | IVC = 552 pbarL/s, MB = 528 mbar+1atm. MB pressure falling. |
| 1435 | IVC = 742 pbarL/s, MB = 155 mbar+1atm and flattening. Gas cylinder is low, close V1a to make sure it isn't empty - G3 rises, good. |
| 1435 | Stop LN2 blowout |
| 1440 | IVC = 520 pbarL/s |
| 1440 | Fill LN2 cold trap bath |
| 1440 | remove hose from MB LN2 fill pipe and put stopper in pipe, for MB pumpout |
| 1445 | Start pumping out main bath with scroll pump. Takes 16 minutes to fall to 1 mbar. |
| 1500 | IVC = 456 pbarL/s |
| 1510 | Pressurize MB with helium to 216 mbar above 1 atm. |
| 1510 | Isolate MB by closing V1a. Pump out line to the G3 volume with Scroll Pump. Isolate pump, then open 1K Pot speedivalve to check pressure: about 0.03 bar. Then pump out 1K Pot (needle valve closed) with Scroll Pump to 0.026 mbar on P2. Then close 1K Pot speedivalve and V4a. Open V1a again to monitor bath pressure. |
| 1515 | IVC = 401 pbarL/s |
| 1520 | Let 63 μbar He exchange gas into IVC. |
| 1536 | Begin initial LHe transfer |
| 1540 | MC(Cernox) = 77.8 K, Sorb = 141.4 K, IVC = 63 μbar, G1(fridge) = 605.8 mbar. G3(MB) = 573 mbar+1atm
note: 3He pump is off, G1 will be a little lower this time |
| 1550 | MC(Cernox) = 77.1 K, Sorb = 132.2 K, IVC = 30 μbar, G1(fridge) = 603.6 mbar. G3(MB) = 491 mbar+1atm |
| 1600 | MC(Cernox) = 69.4 K, Sorb = 105.8 K, IVC = 16 μbar, G1(fridge) = 585.7 mbar. G3(MB) = 443 mbar+1atm |
| 1615 | MC(Cernox)/Sorb = 59.1/54.9 K, IVC = 12 μbar, G1(fridge) = 526.3 mbar. MB = 3.6% / 502 mbar+1atm |
| 1630 | MC(Cernox)/Sorb/1K Pot = 49.9/7.5/6.03 K, IVC = 22 μbar, G1(fridge) = 472.2 mbar. MB = 25.7% / 452 mbar+1atm |
| | NOOO! IVC pressure is rising again!!! |
| 1635 | MC(Cernox)/Sorb/1K Pot = 45.6/7.4/5.96 K, IVC = 54 μbar, G1(fridge) = 472.2 mbar. MB = 37.6% / 458 mbar+1atm |
| 1640 | Close IVC valves, then pump out manifold with Turbo. Pumps down fine, to <0.1 ubar. Open IVC valves again, pressure → 120 ubar |
| | Pretty sure there is no point in continuing the transfer. I see two possibilities: one of the other indium IVC seals has randomly sprung a cold leak, or the stripline elbow is getting extra leaky when it gets cold enough. |
| 1645 | MC(Cernox)/Sorb/1K Pot = 39.1/7.7/6.16 K, IVC = 300 μbar, G1(fridge) = 464.3 mbar. MB = 54.5% / 464 mbar+1atm |
| 1647 | End LHe transfer early @ MB = 42.2% |
| 1700 | MC(Cernox)/Sorb/1K Pot = 25.7/7.2/5.78 K, IVC = 540 μbar, G1(fridge) = 466.5 mbar. |
| 1705 | Start pumping out IVC with Scroll Pump. Pressure barely falls at all. With IVC valves closed it falls below 10 μbar, but stuck around 460 μbar with IVC valves open. |
| 1715 | Scroll on IVC = 340 μbar. |
| 1720 | Pulled the duct tape off the stripline elbow, we'll want to try to leak check this later if possible (pressure way to high to do any leak checking now). |
| 1725 | Tried pushing the stripline elbow around a bit to see if the pressure changes, didn't see any change |
| | Thinking more about it, the evidence suggests that it's not the stripline elbow, I think. If it were happening because the top of the fridge gets cold during a transfer, then we'd expect the leak to disappear when the top of the fridge is warm. Instead, if I recall correctly, the leak was still present until the _fridge_ temperature got up above around 40 K again. Should double check this, and watch this time for when the leak disappears. |
| 1730 | Scroll on IVC = 340 μbar. Stop pumping IVC. |
| 1735 | MC(Cernox)/Sorb/1K Pot = 4.25/5.3/4.26 K, IVC = 540 μbar, G1(fridge) = 523.3 mbar. |
| 1735 | Matt exits lab |
| 1940 | IVC = 250 μbar. Maybe it's going down because it's continuing to cool. That could be an effect that's competing with the leak. Maybe? |
| 2050 | IVC = 400 μbar. |