| 0005 | Tower temperature has risen all of a sudden from 50 mK to 67 mK. Temperature of 1 K pot has also increased to 2.5 K. Pressures in G1 and G2 rising. Why? Helium liquid level is 37.9%… is it lying to us? |
| 0020 | It looks as though the 1 K pot has failed. Tower temperature is above 100 mK and pressures in G1 and G2 are above 500 mbar. Playing around with the needle valve yields no joy. Time to get the liquid helium and see if a transfer solves things. |
| | Stop data series 07110505_2149 on file 19. |
| 0030 | Start LHe transfer. Tower temperature remains above 100 mK, but 1 K pot temperature is dropping, as are the pressures in G1 and G2. |
| | Maybe thoughts that we were becoming extremely efficient at evaporation were premature. It seems as though the helium liquid level sensor has a fault. |
| | Fill N2 cold trap full. |
| 0050 | Tower temperature 94 mK and dropping. I guess the helium liquid sensor must be faulty. |
| 0100 | Helium liquid level 97.0%, but I don't believe it. Usually it takes at least 40 minutes to rach that level if the main bath is empty. I'm going to continue the transfer for a few more minutes. |
| 0105 | Helium liquid level 99.4%. Stop LHe transfer. |
| 0110 | Helium liquid level fell to 96.7%. Very high vapour pressure in main bath. I'm beginning to doubt if the situation is so simple as to blame a “faulty” helium liquid level sensor. |
| 0155 | Fridge seems to have made a recovery. Tower temperature 52.0 mK, 1 K pot temperature 1.52 K, G1 pressure 129 mbar and G2 pressure 124 mbar. Everything seems to be stable. Phew… |
| 2000 | Filled LN2 cold trap. |