2016/06/15 (Wednesday)
| Status | Circulation and 1K Pot stopped, mixture from fridge left open to dump. DCRCs off. |
|---|---|
| 0905 | Tower/MC(H35)/MC(Cernox) = 20/35/19 K. G1 (dump&fridge) = 680 mbar. 1K Pot>7 K, Sorb = 11 K. Main bath = 5.3% |
| 0915 | Pump out Trap 1 to dump through V12a, V5, V9 with 3He pump. Pump for 10 minutes down to 0.5 mbar on G1. |
| 0920 | Isolate Trap 1, then open fridge to dump again by opening V1, V4, V14 (also condenser and still valves open). Pump is off. |
| 0925 | Remove Trap 1 from bath to let warm up. |
| 0940 | Pump mixture out of fridge to dump with 3He pump, through condenser and still valves, V1, V3, V6, V9. |
| 1000 | Fridge down to P1/G1 = 0.032/1.1 mbar. Isolate fridge and stop pumping to dump. |
| 1000 | Dump (G2) = 788.8 mbar. Barometric pressure = 29.69, so adjusted dump pressure is 781.0 mbar. Actually G2 is still creeping up - maybe the mixture is still a little cold, so should measure again after it stabilizes. |
| 1010 | Dump has crept up to G2=790.8 mbar, adjusted = 783.0 mbar. Close V9 and turn off pump. |
| 1020 | Interestingly when we started pumping mix out of fridge, Sorb temperature started to go up. Sorb = 17 K. |
| 1045 | Trap 1 reads 55 mbar of contaminant on P2 (room temperature, pressure flat). Pump out Trap 1 with 4He pump, down to 0.045 mbar in 5 minutes. |
| 1145 | Perform electrical checkouts. The previous problems were seen but there are also new ones: |
Already known problems:
- DIB1 Phonon D Feedback is shorted to chassis: Coil/Return to Chassis = 4.3/9.2 kΩ
- DIB2 Phonon D Feedback is shorted to chassis: Coil/Return to Chassis = 1.2/4.6 kΩ
- DIB1 Qinner Bias to Phonon D QET has too-high resistance, 16 nS (should be 25 nS)
New problem:
- DIB1 Qinner Feedback-to-Drain is open, < 0.1 nS, should be around 19 nS. This could be a problem with the FET or equally well could be a broken Qdrain trace in the stripline or plug or something. UPDATE: later this problem was not observed. I think probably the cable was not plugged into the breakout box firmly enough when this test was take.
| 1200 | Pump out lines to IVC with turbo, then isolate turbo, then open IVC to Pfeiffer gauge. Pressure goes down from 1.9 e-3mbar to 0.30 e-3mbar, then continues to fall. Pretty good indication that there's no He gas in the IVC. |
|---|---|
| 1500 | MC(Cernox)/Sorb = 20/18 K |
| 1510 | Let about 5e-2 mbar He gas into IVC. But IVC pressure quickly falls back to 5.4e-5 mbar, so maybe the gas is liquefying. MC and Sorb temperatures both fall, as thermal contact is made with the ~4K IVC walls. |
| 1625 | MC/Sorb = 17.6/14 K |
| 1630 | Let mixture back into fridge to make thermal contact between fridge guts and GHS. Sorb initially goes up a K but then starts to fall more quickly. |
| 1635 | Try pumping out Main Bath with scroll pump. Before this MB=150 mbar relative on G3. Wait a few minutes but pressure only drops to about 0.7 bar. |
| 1640 | Backfill MB with He gas. After several minutes get it back above one atm, stop backfill at 30 mbar relative. MB pressure continues to increase after that, must still be a little LHe in the bath. |
| 1655 | MC/Sorb = 16.8/10 K. MC slowly falling, Sorb slowly rising. |
| 1705 | MC/Sorb = 16.4/12.5 K. IVC = 6.3e-5 mbar. Will leave mixture in fridge overnight again. |