2016/07/08 (Friday)
| Status | Fridge warming overnight after discovering a blockage. He gas in MB vacuum jacket and IVC. |
|---|---|
| 0800 | MC(Cernox) = 270 K. IVC = 10 mbar. Remove the LN2 transfer tube, it's cool to the touch, probably below dew point. |
| 0805 | Pump IGH to dump, then open V1 and condenser speedivalve to see LHe trap and condenser contents on G1. G1 doesn't increase much, maybe 0.1-0.2 mbar. |
| 0810 | Open still gate valve. P1 barely increases, 6 μbar to 7 μbar |
| 0810 | Try a forward throughput test through LN2 Cold Trap 2. P1 increases, flow is present. P1 rises 0.35 mbar/minute |
| 0820 | Pump mixture from fridge and Trap 2 back to dump |
| 0825 | Try a simplified reverse throughput test: open V1, condenser speedivalve, and still gate valve. Then open V14 to let mix from dump into still. Throughput = 13 mbar/min on G1. |
| 0830 | Begin pumping both sides of fridge to dump. Will leave it for a while. |
| 0840 | Apply 100 mW power to Still heater |
| 0940 | Stop pumping fridge to dump. Dump (G2) = 791.5 mbar. |
| 0940 | MC(Cernox) = 277 K. LN2 transfer tube is still cold to the touch. |
| 1110 | MC(Cernox) = 281 K. LN2 transfer tube is still cold to the touch. |
| 1415 | MC(Cernox) = 286 K. LN2 transfer tube is still cold to the touch. IVC = 16 mbar. |
| 1425 | Isolate IVC. P1: 17ubar. Isolate Fridge lines and close all valves on IGH to cease pumping on fridge lines with scroll pump. Prepare to pump out dewar jacket with scroll pump and to pump out fridge lines with Turbopump. |
| 1450 | Attach turbopump to He4 pump manifold and commence turbopumping out fridge lines through V5a, V2a, V7, V2, V1, condenser line speedivalve, V3, and gate valve. This will pump on both sides of the fridge. Close manual valves on dump to prevent any failures in V14 or V4 to cause loss of mixture. |
| Turbopump pressure sensor currently reads 3.0E-5 mbar. P1: 19ubar, P2: 10ubar, G1: 0.5mbar. | |
| 1615 | P1 (fridge) = 18 μbar, P2 (pump line) = 10 μbar, Turbopump gauge = 7.4 nbar. |
| 1620 | Valve out turbopump for five minutes, now: P1 (fridge) = 18 μbar, P2 (pump line) = 13 μbar, Turbopump gauge = 12 μbar. |
| Based on the P1 pressure, Turbopump does not seem to be an improvement over the 3He pump. Perhaps it's more a matter of displacement than minimum pressure. | |
| 1630 | MC(Cernox) = 290 K. LN2 transfer tube is still somewhat cool to the touch. But probably above dew point (not that that is relevant in the fridge lines). Begin pumping on MB vacuum jacket with scroll pump. |
| 1640 | Cease pumping on fridge lines with turbopump. Close all valves on IGH and turn off turbopump. |