| 0010 | Prepare to blow out LN2. Isolate vacuum pump; pressure in IVC 1.9E-3 mbar, rises to 1.9E-2 mbar after pump is isolated. Quite a bit of nitrogen still left in IVC. Perhaps it has not been pumping on it for long enough. |
| | Mixing chamber temperature 77.4 K. |
| | Background He leak rate 3.4E-9 mbar l/s: good enough. Open He gas supply and start blowing out LN2. Pressure in G3 223 mbar. |
| 0025 | Start cryocleaning mixture through both cold traps. Open valve 6 to 13.8%. |
| 0040 | Pressure in G2 a little low: open valve 6 to 13.9%. |
| 0045 | Open valve 6 to 14.0%. |
| 0100 | Increase pressure in G3 to 347 mbar. He leak rate rises quickly, but still within acceptable levels. |
| 0110 | Fill N2 cold trap full. |
| 0150 | Increase pressure in G3 to 409 mbar. He leak rate has been rising for some time, but there is no spike so its probably safe to assume this is background. Currently stands at 1.96 mbar l/s. |
| 0155 | LN2 out of main bath. Close He supply. |
| 0215 | He leak rate increases to 2E-3 mbar l/s! Isolating IVC by closing both valves closest to fridge causes leak rate to decrease sharply. This indicates that the leak is coming from within the IVC. This is confirmed when leak rate increased again after valves were opened. |
| | Sprayed helium around flanges above IVC, but no increase in leak rate was observed. This might be due to the high background. It might be worth trying this again after pumping out the IVC overnight. |
| | Perhaps it makes sense that there is a leak: it has been very difficult to pump out the nitrogen exchange gas. Why didn't it show up before? |
| | Pump mixture into dump prior to throughput test. |
| 0245 | Conduct throughput test: 25 mbar/min. Much better: perhaps mixture needed more cleaning. Try again to make sure this isn't a fluke. |
| 0255 | Pump main bath. He leak level decreases rapidly, plateauing at 1E-6 mbar l/s. Everything seems to indicate that the bottom IVC flange is the source. |
| 0310 | Conduct throughput test: 38 mbar/min. It just keeps getting better. Can we trust these results? Pump mixture into dump. |
| 0320 | Fill main bath with helium gas. Leak rate increases rapidly, which seems to point to a leak inside the IVC. Levels off at 6.9E-6 mbar l/s. |
| 0330 | Time to warm up. Depressurise main bath and add 10 mbar of N2 exchange gas to IVC. |
| 0340 | Conduct throughput test: 38 mbar/min. Looks good. Pump mixture to dump in preparation for overnight cryocleaning. |
| 0350 | Croclean mixture overnight through nitrogen cold trap 1: valve 6 open 13.8%. |
| | Open valves 11b and 8 to pump out mixture from cold trap 2 in preparation for cleaning in a few hours. |
| 0918 | Pump out N2 exchange gas to conduct another leak check before dropping the dewar. |
| 0929 | IVC He: 3.7E-4cc/s with pumping station on. There must be a leak. I'll drop the dewar. |
| 0933 | FIll IVC with 3mbar N2 exchange gas. |
| 1013 | Dewar is lowered. Blowing warm air to the fridge and the dewar to warm them up faster. |
| 1245 | Interrupt cryocleaning to clean nitrogen cold trap 2. Pump mixture to dump. |
| 1325 | Pressure in G2 is 599 mbar. At the start of this run, pressure in G2 was 643 mbar. Where has the mixxing mixture gone? |
| | Open gate valve on fridge to see if any is trapped. Pressure in P1 rises from 0.016 mbar to 0.02 mbar, and then drops again. Pressure in G2 remains unchanged. There appears to be nothing trapped in the pressure line. |
| | Open valve 1 with condenser line speedivalve closed to see if anything is trapped in helium cold trap. Pressure in G1 does not change from 0 mbar. There is no mixture here. |
| | Open valve 12b to ensure everything is out of cold trap 2. Now pumping on both sides of cold trap. Pressure in G1 does not increase from 0 mbar. Cold trap appears to be empty. |
| | Close gate valve and all valves on IGH except 6, 8b, 9 & 11b. Pressure in P1 is 0.016 mbar. |
| | Turn on He-4 pump and evacuate 1 K pot line (needle valve is closed). |
| 1340 | Evacuate lines from vent on auxiliary side (valves 2a & 5a), and then turn He-4 pump off. Close valve 8 and open valve 7. Extract cold trap 2 from nitrogen bath. Pressure in P2 0.02 mbar. Close valve 6. |
| 1400 | Pressure in P2 jumps to 1 bar. Trap looks like it was very dirty. Turn on He-4 pump and evacuate. Expose trap to heat gun for 1 hour. |
| 1450 | It's difficult to know pressure in trap: when turned off, He-4 pump might suck air back into the lines. Close valve 11b and open 12b to monitor pressure rise on G1. Pressure rises to 0.2 mbar. Heat up trap: pressure rises to 1 mbar. Looks like it is clean (perhaps it wasn't even dirty). Open valve 2 to pump out contents. |
| 1505 | Place trap back in main bath. Close all valves from He-4 pump to trap. Wait for it to cool down. |
| | Fill N2 cold trap full. |
| 1520 | Start cryocleaning through cold trap 2. Open valve 6 13.5%. |
| 1735 | Mixing chamber temperature 278 K. Start pumping out N2 exchange gas. |
| 1910 | Interrupt cryocleaning for leak checks. Pump mixture into dump. |
| | Leak check 1: spray helium around IVC flanges. Background helium leak rate 4E-7 mbar l/s. We should see something as leak was rather large. We see nothing. Its likely that this is a cold leak. |
| | Leak check 2: feed mixture into mixing chamber via pumping line through valve 14. Close valve 6. No increase in background leak rate was witnessed. We can try this test again at liquid nitrogen temperatures. |
| | Leak check 3: feed mixture into mixing chamber via condenser line through valve 4. Close gate vale. No increase in background leak rate was witnessed. As above, we can try this test again at liquid nitrogen temperatures. |
| | Pump mixture into dump. |
| 1915 | Overpressurise IVC with nitrogen gas in preparation for opening. Rig up mini-clean room. |
| 2139 | Bottom In seal was replaced. No problems during quick electrical check. Start pumping IVC. |