| 0040 | Pump out exchange gas at mixing chamber temperature 11 K. |
| | Cease helium transfer. Helium liquid level 92.8%. |
| 1315 | Filled LN2 cold trap. |
| 1335 | Cleaning mixture. G2: 444 mbar, G1: 424 mbar |
| 1500 | Mixing chamber temperature is a little shy of 4.2 K. IVC pressure is 1.4E-5 mbar. Mixing chamber temperature should have risen overnight to 7 K or so, and IVC pressure should be <1E-6 mbar. Everything seems to point towards either a leak from the main bath to the IVC or trapped exchange gas. IVC pressure was <1E-5 mbar at 77 K, which would imply that if this is a leak, it would be one that only occurs at liquid helium temperatures. |
| | Condensing the mixture probably won't work. Turn on mixing chamber heater to 20.0 mW in an attempt to warm up the IVC, and hence increase the vapour pressure to pump out an residual exchange gas. Mixing chamber increases to just over 5 K. Evacuate IVC overnight. Might try to condense mixture tomorrow. If this doesn't work, we'll have to lower the dewar and reseal the IVC on Monday. The earliest we can get liquid nitrogen is Tuesday. |