2019/07/17 (Wednesday)
| Setup | DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2 → gender changer ?/3/2 → HVConn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1) DCRC33(2) → 1kV power supply → HV input Three walls of the lead/poly shield are up. |
|---|---|
| Fridge failure yesterday. Last night I closed circulation and opened the fridge to the dump, remotely. It looked like maybe a sudden boiloff of helium in the IVC. But…. | |
| 0835 | upon arrival, find that the pumps are off. Maybe the fridge failure was just a power interruption? |
| 0835 | Close 1K Pot speedivalve. Then reset fuse box - pumps restart. |
| 0840 | Tower/1K Pot/Sorb = 5.5/>7/9.5 K. MB = 28.7% |
| not sure what to make of the >4K temperatures. It may be that we now have a lot of helium gas in the IVC. Could be that that's a symptom of the fridge failure rather than a cause. Should pump it out. Not this will be “blind” as we have no Pfeiffer gauge. | |
| 0845 | Connect scroll pump to pump manifold, pump out manifold up to IVC valves (which are closed) |
| 0850 | Switch to pumping with turbo pump |
| 0855 | Stop pumping on manifold, then open IVC to pump manifold. Also have the mechanical valve in line - watch that valve - no increase when I open the IVC. No reaction from the fridge temperatures. |
| 0855 | Close valve to mechanical gauge, thecdms:k100:run_diary:20190525n open valve to turbo pump. Now pumping IVC with turbo pump. |
| 0910 | Close valve to 1K Pot pump, then open speedivalve. P2 rises off scale. Close needle valve. |
| 0915 | Pump out 1K Pot in steps, then start pumping it continuously. |
| 0920 | Open 1K Pot needle valve → 5°. 1K Pot → 3.0 K / 7 mbar Open 1K Pot needle valve → 10°. 1K Pot → 2.8 K / 15 mbar Open 1K Pot needle valve → 15°. 1K Pot → 2.4 K / 26 mbar |
| 0925 | Open 1K Pot needle valve → 20°. 1K Pot → 1.9 K / 90 mbar. Tower temperature falling, 5.4→4.0 K |
| 0930 | Fill LN2 cold trap full. |
| 0935 | P2 is decreasing, 1K Pot = 1.7 K / 36 mbar, Tower = 2.7 K |
| 1010 | 1K Pot pressure jumped to 85 mbar and is oscillating +/- 10 mbar. 1K Pot = 1.7 K, Tower = 2.6 K. G1/G2 = 202/191 mbar and have been falling. |
| 1220 | 1K Pot = 1.7 K / 85 mbar, pressure is oscillating as normal. Looks like it's working nicely. But Tower is not cooling, looks stuck at about 2.5 K. This is a bad sign - it may indicate there's still a lot of helium in the IVC. |
| 1225 | Switch to Cernox thermometer to better compare to initial Run70 cooldown. MC(Cernox) = 2.48 K Last time it flattened out too, but at a lower temperature, 2.1 K. We could go ahead and try circulation I guess. G1/G2 = 151/143 mbar and pretty flat. Last time they flattened a lot lower at 61 mbar. |
| 1400 | Commence LHe tranfer. MB=18.5%. Using 100L dewar. He gas cylinder is empty!? When did that happen? Replace it with a new one. |
| 1442 | Cease LHe transfer. MB=91.3% |
| 1457 | Close V9, leaving 132 mbar in the dump. Start circulation through Trap 1. V6 → 12.5%. No immediate changes. |
| 1500 | V6 → 12.8%. No changes, MC (Cernox) = 2.5 K, G1 = 145 mbar |
| 1503 | V6 → 13.0%. Condenser flat at 149 mbar. MC (Cernox) → 2.5 K. |
| 1507 | V6 → 13.2%. Condenser flat at 150 mbar. MC (Cernox) → 2.5 K. |
| 1510 | V6 → 13.4%. Condenser peaks at 189 mbar. MC (Cernox) → 2.4 K. |
| 1515 | V6 → 13.6%. Condenser peaks at 357 mbar. MC (Cernox) → 2.0 K. |
| 1519 | V6 → 13.8%. Condenser peaks at 450 mbar. MC (Cernox) → 1.6 K. Still → 500 mbar. |
| 1526 | V6 → 14.2%. Condenser peaks at 400 mbar. MC (Cernox) → 1.4 K. Still → 9.5 mbar. |
| 1534 | V6 → 14.6%. Condenser peaks at 350 mbar. MC (Cernox) → 1.3 K. Still → 5.0 mbar. |
| 1545 | V6 → 15.0%. Condenser peaks at 350 mbar. Tower → 1.3 K. Still → 4.0 mbar. |
| 1551 | V6 → 15.4%. Condenser peaks at 368 mbar, rising slowly. Tower → 900 mK. Still → 3.0 mbar. Cooling is behaving a bit strangely here, the condenser pressure G1 continues to slowly rise as the tower temperature continues to fall. This has been ongoing for 30 minutes and doesn't show any signs of stopping. (1620) Tower → 900 mK. G1 - > 366 mbar |
| 1600 | Fill LN2 Cold Trap Bath Full |
| 1625 | V6 → 16.0%. Condenser peaks at 377 mbar. Tower → 800 mK. Still → 1.9 mbar. |
| 1630 | V6 → 16.4%. Condenser peaks at 379 mbar. Tower → 717 mK. Still → 1.4 mbar. |
| 1643 | V6 → 16.8%. Condenser peaks at 380 mbar. Tower → 650 mK. Still → 1.1 mbar. |
| 1646 | V6 → 100%. Condenser peaks at 386 mbar. Tower → 520 mK. Still → 0.32 mbar. 1K Pot = 1.7K / 90 mbar |
| 1730 | Tower = 81 mK, Still = 0.260 mbar, Condenser = 311 mbar, 1K Pot = 1.72 K / 110 mbar |
| 1730 | Open V14 to let the remaining mix out of the dump and into circulation. P1(Still) rises off scale, falls again after a minute. Condenser peaks at 480 mbar. Tower → 175 mK then falls. 1K Pot peaks at 1.79 K / off-scale mbar then settles. |
| 1740 | Tower = 143 mK, Still = 4.0 mbar, Condenser = 162 mbar, 1K Pot = 1.67 K / 40 mbar. Pot temporarily rises then dips, then settles to something normal. |
| 1750 | Tower = 85 mK, Still = 1.5 mbar, Condenser = 137 mbar, 1K Pot = 1.71 K / 80 mbar. |
| 1800 | Tower = 79 mK, Still = 0.8 mbar, Condenser = 133 mbar, 1K Pot = 1.71 K / 85 mbar. Close V14. |