| 0915 | P1=6 ubar, G1=1.4 mbar and G2= 200 mbar, rising from 0 mbar last night. This strongly suggests that there is still a leak present in the pump area. |
| 0950 | Close V1 and V3 and isolate and turn off the turbo pump. Tighten all flanges on He-3 pump lines (a few flanges were noticeably loose), and open V13A to begin pumping out G2. |
| 1025 | While working on an unrelated task (reconnecting He cold trap to leak checker), we noticed the He-3 pump suddenly become louder. This rise in noise corresponded to G2 suddenly jumping to 69 mbar from the previous 0 mbar. |
| 1050 | Perform throughput test without using He-3 pump, as it appears to have a leak. Add 250 mbar He gas through vent, V7 and V2 to G1. Open gate and condenser line speedivalves. Notice no change in P1 from initial 6 ubar as G1 drops to 35 mbar. This suggests that a blockage is present. |
| 1130 | With G1=33 mbar, P1=9 ubar and G2= 17.9 mbar, open 5A, 2A, 7, 11A and 13A to pump on G2. |
| 1145 | P1=11 ubar, G3=33 mbar, G2= 0 mbar. Close vent valve and V13A, open V6 to see if we can pump out fridge lines. |
| 1215 | Close V6, open V12B to pump out cold trap 2, and pull out of bath. G1=5.5 mbar and G2 rose to ~44 mbar. |
| 1425 | Stop pumping on G2 but continue pumping on cold traps by closing V13A. |
| 1540 | Install speedivalve in back of cold trap 2. Begin pumping on condenser line with turbo pump. |
| 1545 | Commence leak check on He cold trap with new low-pressure flange. Begin with background rate of 6.0E-10 mbarL/s. No sign of leak on cold trap, bellows that leads to condenser line, or flanges connecting He cold trap to leak checker, even with movement of the cold trap and bellows (very slight background rate increase while these are tested). However, a small spike of roughly 1.0E-9 mbarL/s occurred at a particular point on the bellows that would lead to the fridge, a few inches above where the bellows meet. After this initial rise occurred, the background rate began to rise, reaching 6.5E-9 mbarL/s as we continued our tests for the next ~30 minutes. With this increase it was not possible to determine whether bending or spraying the flange had any affect on the leak rate. |
| 1800 | Close V1 and V3 to stop pumping on condenser line with turbo pump. |
| 1920 | Attach He cold trap to condenser line port on IGH and speedivalve before V6 on He-3 pump intake. This effectively makes a system that goes from the V1 on IGH to He cold trap to V6 on IGH. Pump on He cold trap with scroll pump through vent, V7, V2, and V1. |
| 1930 | Notice that G2 has fallen from 17 mbar (about 2 hours ago) to 9 mbar and is still falling. It appears that G2 started falling more steeply since we began pumping on G1 with the scroll pump at 19:20. There is no apparent connection between G2 (which is completely isolated from the rest of the IGH) and G1/fridge lines. Perhaps V6 is leaky as well? |
| 2025 | Lower dewar. Notice that flange on Gate Valve on the non-fridge-side is rather loose. Tighten flange, and think about how this might be where air is leaking in to pump (if V6 is in fact leaky). Paranoia abounds. |
| 2100 | While lowering the dewar, notice that G2 begins to climb from roughly 7 mbar. Stop lowering dewar once it has dropped roughly 6 in, as G2 begins to climb rapidly and has already reached above 400 mbar. Turn off He-3 pump, and G2 stops rising and begins to fall slowly to about 360 mbar. While it is falling, stop pumping on He cold trap, isolate turbo pump and begin pumping through vent with scroll pump. Open V13A and V11A to begin pumping on G2 with scroll pump. G2 begins to fall. At this point notice loose gate valve flange (see above). Continue lowering the dewar. While lowering dewar, G2 continues to sporadically begin climbing in value (although it is still being pumped on by scroll pump). Whenever G2 reaches above 100 mbar, turn off He-3 pump, give G2 a few minutes until it reads below 30 mbar, and then turn He-3 pump back on. Initially G2 will continue to drop, but within 2 to 3 minutes it will begin rising again; when this occurs repeat process of turning off pump. Once the dewar had been lowered roughly 25-30 in, G2 stops increasing and gets pumped down to zero. After about 5 minutes, close V13A and V11A, and start pumping on He cold trap with turbo pump once more. Continue lowering the dewar, with G2 very slowly rising to about 8 mbar. During this entire ordeal, G2 was isolated from the rest of the lines, so we are unsure why the change in temperature resulted in G2 rising. P2 (on the other side of closed V6) stayed at <.13 mbar while the dewar was being lowered, and G1 stayed at ~1 mbar. |
| 2130 | Once dewar has been lowered stop pumping on He cold trap with turbo pump and begin pumping on He-3 pump exhaust with scroll pump, until G2 reaches 0 mbar. Adjust setup to allow pumping on He cold trap through V1, V2, V7 to vent, V2A and V5A with turbo pump while G2 gets pumped on through He-3 pump exhaust speedivalve with scroll pump. Currently G1=0.7 mbar, P1=0.1 mbar, and G2=0.0 mbar, with a fridge temperature of 97 K. Leave overnight to hope for the best. |