2021/03/25 (Thursday)
- Lab in-person: Derek
- Virtual partner: Matt
| Status | Run 74 in progress. Warming the fridge to fix short and presumed thermal touch. DCRCs off, disconnected. All mixture in dump. 1K Pot isolated. Turbo pump still pumping on IVC, no gas in cryostat vacuum jacket. Fridge open to IGH. |
|---|---|
| 0920 | MB = -1.0% (minimum) |
| 1020 | Tower/Sorb = 19.5/22.2 K, P1(fridge) = 0.30 mbar |
| 1020 | Recovery = 427000.18 cuft (10:20:23) / 15.1 cuft/hr |
| 1200 | Around this time the fridge pressure (P1) started increasing and rose significantly. At this time Tower/Sorb = 20/23 K. The hydrogen boiling point is 23 K, so this could well be hydrogen boiloff. |
| 1405 | Tower/Sorb = 20.0/24.5 K, P1(fridge) = 3.8 mbar |
| 1410 | Recovery = 427055.08 cuft (14:10:23) / 13.6 cuft/hr |
Warmup todo list:
- Close V12b speedivalve, Condenser speedivalve, Still gate valve (and all IGH valves)
- Stop pumping the IVC and slowly let some helium into it. Roughly (1 bar) × (Tower temperature) / (300 K) or a little less. Use mechanical gauge above Swagelock valve to measure pressure.
- Let some helium into the cryostat vacuum jacket. A few mbar in the vacuum manifold and hose, then open the vacuum jacket valve to let it in.
| 1410 | Derek enters lab |
|---|---|
| 1415 | Close V12b speedivalve |
| 1415 | Turbo on IVC = 12 nbar. With Turbo valved out, IVC → 140 nbar. |
| 1425 | Let helium into the IVC. Targeting 2/30 bar or a little less, so that it will be near 1 atm at 300 K. Tower and Sorb temperatures quickly fall to around 4 K. Also recovery speeds up, to around 100 cuft/hr. |
| 1430 | Switch from Tower thermometer to Cernox(MC) thermometer |
| 1450 | Adjust pressure of helium in IVC to about 0.063 bar. |
| From 14:45 to 15:30 the recovery rate gets slow, only around 12 cuft/hr. Then it speeds up again. I guess maybe there was some activity in the recovery system, Mike filling a Dewar or something. | |
| 1510 | MC(Cernox)/Sorb = 6.38/15.2 K, P1(fridge) = 2.4 mbar. Sorb is still cooling. |
| 1520 | Connect hose from turbo pump manifold to cryostat vacuum jacket port. |
| 1525 | Let 2.5 mbar He gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum Jacket → 0.074 mbar. MC and Sorb temperatures start rising |
| 1530 | Recovery = 427090.09 cuft (15:30:17) / 125 cuft/hr |
| 1555 | MC(Cernox)/Sorb = 9.5/17.8 K, P1(fridge) = 3.8 mbar. |
| 1600 | Recovery = 427130.22 cuft (16:00:00) / 61 cuft/hr |
| 1610 | Let 4.6 mbar He gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum Jacket → 0.12 mbar. MC and Sorb rise faster, recovery speeds up |
| 1615 | Recovery = 427149.92 cuft (16:15:00) / 141 cuft/hr |
| 1615 | Derek exits lab |
| 1630 | MC(Cernox)/Sorb = 13.1/26.3 K, P1(fridge) = 4.0 mbar. |
| 1640 | Recovery = 427194.86 cuft (16:40:00) / 61 cuft/hr. Rate is slowing, maybe LHe is almost boiled off. |
| 1650 | MC(Cernox)/Sorb = 25.1/38.7 K |
| 1722 | Recovery = 427208.02 cuft (17:22:30) / 14 cuft/hr. |
| 1830 | MC(Cernox)/Sorb = 51.5/86 K |
| 2200 | Recovery = 427217.755 cuft (22:00:00) / 0.69 cuft/hr. |
| 2230 | MC(Cernox)/Sorb = 89.4/167 K |