2021/03/31 (Wednesday)
- Lab in-person: Matt
- Virtual partner: Zach
| Status | Run 74 in progress. Warmed the fridge to fix short and thermal touch. Helium gas in cryostat vacuum jacket, partially pumped out. Mixture cryocleaned twice. IVC sealed and pumping overnight. |
|---|---|
| 1220 | Matt enters lab. |
| 1225 | Turbo on IVC = 22 nbar. With Turbo valved out for 1 minute, IVC = 220 nbar. |
| 1225 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.5% |
| 1230 | Increase V6 → 12.7% to restart flow |
| 1240 | Increase V6 → 12.8% to speed up flow |
| 1250 | Increase V6 → 12.9% to speed up flow |
| 1335 | Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 570-665 mbar. Pump mixture to dump. Removed 6.2 mbar. |
| 1240 | Retighten IVC bolts |
| 1245 | Leak detector on IVC with Turbo valved out: 3300 pbarL/s. That's high. Last time it was 6 pbarL/s. With IVC valves closed, LD → 18 pbarL/s. So it's not a problem with the pump manifold. |
| 1250 | Spray helium liberally around IVC joint, also around stripline elbow. Not seeing any increase. |
| I guess it's very likely that the bottom indium seal failed. I can't see any leak by squirting it, which may mean the leak is less than 10 pbarL/s? Kinda strange but it's always hard to locate a leak when the LD is reading so high. I think I'll have to try again with the IVC seal. | |
| 1325 | Start slowly filling IVC with N2 |
| it just occurred to me - since we filled the IVC with helium for the warmup, maybe there's a lot of trapped helium. Maybe I should just try an N2 flush and pump it out again. | |
| 1335 | Fill IVC slowly with N2, up to slight overpressure |
| 1350 | Start gently pumping out IVC with Scroll Pump |
| 1405 | IVC falls below 0.1 mbar, switch to Turbo Pump |
| 1410 | Start cryocleaning mixture through LN2 Cold Trap 2, V6 = 12.8% |
| 1425 | Increase V6 → 12.9% to restart flow |
| 1430 | Increase V6 → 13.0% to speed up flow |
| 1455 | Increase V6 → 13.1% to speed up flow |
| 1510 | Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 570-790 mbar. Pump mixture to dump. Removed 5.1 mbar. |
| 1415 | Turbo on IVC = 74 nbar. With Turbo valved out for 1 minute, IVC = 860 nbar. |
| 1425 | Turbo on IVC = 46 nbar. |
| 1430 | Check LD on IVC with Turbo valved out. Goes up to around 3500 pbarL/s, continues to creep up - about the same as before |
| 1430 | Turbo on IVC = 46 nbar. With Turbo valved out for 1 minute, IVC = 540 nbar. |
| Let's try another N2 flush | |
| 1435 | Start filling IVC slowly with N2. Fill to a little over 1 atm. |
| 1445 | Start gently pumping out IVC with Scroll Pump |
| 1455 | IVC falls below 0.1 mbar, switch to Turbo Pump |
| 1540 | Turbo on IVC = 30 nbar. |
| 1545 | Pump on IVC with LD, close Turbo valve and wait 1 minute: 3140 pbarL/s. This seems a little better than before. |
| 1555 | Turbo on IVC = 30 nbar. With Turbo valved out for 1 minute, IVC = 300 nbar. |
| 1600 | Pump on IVC with LD, close Turbo valve and wait 1 minute: 3010 pbarL/s. |
| 1605 | Matt exits lab |