| 0955 | Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 538 mbar before Step 3, then it falls to 66 mbar, then rises. Throughput = 41.4 mbar/min. Slightly lower than last time, 2021 December 1 |
| 1000 | Open mixture to both sides of the fridge and cold LN2 Trap 1. |
| 1015 | Electrical checks on all three cables. Everything looks good except the issue discovered yesterday: motor coil X2 is open. |
| 1020 | Turbo on IVC = 10 nbar. With Turbo valved out for 1 minute, IVC = 190 nbar. |
| 1020 | Leak Detector on IVC ~ 1700 pbarL/s. Switch back to pumping with turbo. |
| 1155 | Turbo on IVC = 7.4 nbar. With Turbo valved out for 1 minute, IVC = 190 nbar. |
| 1020 | Leak Detector on IVC ~ 1200 pbarL/s. Switch back to pumping with turbo. |
| 1205 | IVC = 1250 pbarL/s |
| 1205 | Begin blowing out LN2. Main bath (G3) → 675 mbar+1atm |
| 1210 | IVC = 1320 pbarL/s, MB = 666 mbar+1atm |
| 1220 | IVC = 1300 pbarL/s, MB = 647 mbar+1atm |
| 1225 | IVC = 1280 pbarL/s, MB = 642 mbar+1atm |
| 1230 | Fill LN2 cold trap bath |
| 1235 | IVC = 1240 pbarL/s, MB = 637 mbar+1atm |
| 1240 | IVC = 1220 pbarL/s, MB = 646 mbar+1atm |
| 1245 | IVC = 1210 pbarL/s, MB = 285 mbar+1atm and falling, looks like blowout is about over |
| 1245 | IVC leak signal starts rising. |
| 1238 | IVC = 18000 pbarL/s and rising. Crap. |
| 1250 | MB = 200 mbar+1atm and flattening |
| 1250 | Stop LN2 blowout |
| 1300 | IVC = 61200 pbarL/s. |
| 1300 | Start pumping out Main Bath. We'll see if the leak signal falls again - that will verify that there's a leak at an IVC indium seal in the MB. |
| 1305 | IVC falls to 38500 pbarL/s when MB falls to 0.5 atm. |
| 1310 | IVC falls below 10000 pbarL/s as MB falls low enough for P2 to be in range. |
| 1315 | IVC = 1800 pbarL/s, MB = 0.5 mbar. |
| 1315 | IVC = 1320 pbarL/s, MB = 0.32 mbar. |
| | The situation is pretty clear: the bottom indium seal has failed, we have a leak (and as usual it didn't show up until 77K). We can't cool like this, we need to warm up. |
| | UPDATE: realized that I used the wrong indium for the seal. Used 1mm diameter, didn't see the spool of 1.5 mm diameter. |
| 1345 | Fill MB with N2 gas. Leak signal goes up but not very much, → 1660 pbarL/s |
| 1350 | Start slowly filling IVC with N2 gas. Fill to about 100mbar on Pfeiffer gauge, 0.08 atm on mechanical gauge. Temperature didn't budge so I'll stop there, maybe the N2 is condensing. |
| 1410 | Let 100 mbar N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 4.0 mbar |
| 1430 | Sorb = 135 K and rising. MC(Cernox) has warmed slightly, 77.9 K |
| 1435 | Let 100 mbar N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 7.4 mbar |
| 1440 | Let 100 mbar N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 10 mbar |
| 1540 | MC(Cernox)/Sorb = 82.8/173 K and rising. |
| 1540 | Let 100 mbar N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 14 mbar |
| 1540 | Let 100 mbar N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 16 mbar |
| 1545 | Let 100 mbar N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 19 mbar |
| 1545 | Let 100 mbar N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 22 mbar |
| 1600 | Let about 0.30 atm N2 gas into IVC. MC(Cernox) = 86.7 K, so this should be slightly over 1 atm at room temperature. |
| 1705 | MC(Cernox) = 101.9 K, warming at 13.2 K/hr. Assuming Troom = 71 F this implies a warming tau of 14.6 hours. That means the time to reach 0 C is 32 hours, which would be 1 am Thursday morning. |
| 1740 | Turn MC and Still heaters on to 20 mW each (couldn't hurt) |
| 1745 | MC(Cernox)/Sorb = 109.4/244 K and rising. |
