2019/05/22 (Wednesday)
| Status: | 1K pot clogged at 4K, warming back up. Helium exchange gas in cryostat jacket and IVC. |
|---|---|
| 1025 | MC(Cernox) = 187.7 K, Vacuum jacket = 0.22 mbar At this rate, we will hit 273 K around 2000 tomorrow. |
| 1030 | Let two hose-lengths He gas into cryostat vacuum jacket. Vacuum jacket → 1.4 mbar |
| 1033 | We've had the IGh valves closed, but left the condenser speedivalve and still gate valve open as we warm. P1 hasn't changed from 0.34 mbar since we pumped the mix out of the fridge at around 5 K, so we probably did a good job of getting it all out. Close condenser speedivalve and still gate valves. |
| 1025 | P2 = 0.3 mbar, up from 0.14 mbar yesterday, but doesn't seem nearly as leaky as last week. |
| 1035 | LN2 Trap 1 is room temp. Check contents: 2.7-1.3 = 1.4 mbar on G1. This accumulated during the cooldown to 4K through a combination of gentle flow through the trap and fridge while cooling to 77K and passive cleaning while cooling to 4K. Pump out with 4He pump from both sides of the trap by opening both V2 and V11A. |
| 1055 | Put cold trap 1 in LN2 bath, top off LN2 bath. |
| 1117 | Let's see what the pressure in the IVC is doing. Close off Dewar jacket and connect pump manifold to IVC. Pump down manifold with scroll, then turbo pump. Close off turbo pump, pressure is 0.25 ubar Open valves to IVC, pressure is 6.3 mbar. |
| 1128 | Let's bump this up a little to 10 mbar to speed up warmup. We're at about 200 K now, so that should only give us 15 mbar at 300 K. |
| 1131 | Let He exchange gas into IVC to give an IVC pressure of 10 mbar. Close IVC valves, connect pump manifold back to dewar jacket. |
| 1140 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.4% G2 start to rise above 900 mbar before V6 is even to 12.4%. Close V6 and open V9 and V13A. Just leave it like this for a bit, with both sides of the dump open to cold trap 1. |
| 1145 | Pumping down pump manifold with scroll then turbo pump. After switching to the turbo below a few e-2 mbar as usual, unplug scroll pump. When I do this, the pumping station briefly flashes a warning about pressure changes, even though the valve to the scroll pump is well closed and pressure on gauge doesn't change. Odd. |
| 1150 | Restart cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.4% This time, G2 just rises a little bit and starts to fall again. |
| 1155 | With pump manifold and hose up to dewar jacket valve down to 1e-4 mbar (with pumps valved out), open dewar jacket valve so we can again monitor dewar jacket pressure. Now it reads 1.0 mbar, up from 0.22 mbar a few hours ago. That doesn't seem right, maybe this gauge is still being weird. |
| 1200 | Increase V6→12.9% to restart flow. |
| 1225 | Increase V6→13.1% to restart flow. |
| 1230 | MC(Cernox) = 202.0 K |
| 1250 | Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 580-630 mbar during the main cleaning, and 580-980 mbar when initially trying to get flow established. Pump mixture to dump. Removed 3.7 mbar. |
| 1325 | Remove trap 1 from LN2 bath to warm. With 3He pump on and v9 open, G2 = 733.7 mbar in dump. |
| 1409 | Close off main bath from recovery system. Loosely cap a main bath port by setting a kf cap over it with an oring to hold it down. |
| 1506 | LN2 Trap 1 is room temp. Check contents: 4.3-0.6 = 3.7 mbar on G1. Pump out with 4He pump from both sides of the trap by opening both V2 and V11A. |
| 1530 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.4% |
| 1532 | MC(Cernox) = 223.5 K Warming rate has increased slightly since adding more exchange gas this morning. Now it's on track to hit 280 K at 0800 tomorrow. |
| 1540 | Increase V6→13.1% to restart flow. |
| 1600 | Increase V6→13.2% to restart flow. G2 peaks 805 mbar. On second thought I may have been premature on opening this further but it didn't seem to affect much. DS |
| 1630 | Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 590-805 mbar during the main cleaning. Pump mixture to dump. Removed 3.4 mbar. |
| 1650 | Remove trap 1 from LN2 bath to warm. |
| 1700 | MC(Cernox) = 232.7 K, Vacuum jacket = 1.0 mbar |
| 2030 | MC(Cernox) = 250.5 K |