| 0045 | Start pumping out N2 exchange gas from IVC. |
| 0335 | Pressure in IVC has been 1.6E-2 mbar for quite some time. It is possible that we have a leak. However, this would have to be a pretty big one which we should have seen at room temperature. |
| 0345 | Background helium leak rate 1.2E-8 mbar l/s. Pressure in IVC poor, but hopefully good enough. Commence blowing nitrogen out of main bath. |
| | Pump mixture into dump in preparation for throughput test. |
| 0400 | We have a leak! Strangely, it can't be the bottom flange. We have leak checked all these flanges at 77 K during Run 30, but could thermal cycling explain this one? Let's see how bad it is. |
| 0410 | Helium leak rate seems to have plateaued at 7.8E-7 mbar l/s. Potentially, we could still operate with this leak. Interestingly, mixing chamber temperature has been decreasing even when N2 exchange gas was evacuated. Additionally, the pressure in the IVC is rather high at 0.16 mbar. Could this simply be trapped nitrogen? |
| 0415 | Helium leak rate is now 1.1E-6 mbar l/s. Potentially we cannot live with such a leak rate. Keep monitoring leak rate as nitrogen is blown out. |
| 0455 | Fill N2 cold trap full. |
| 0520 | Nitrogen blown out. Helium leak rate jumped to 2E-2 mbar l/s towards the end, implying that there is a huge leak on the bottom flange. We definitely can't live with this leak rate. IVC pressure is 3.4E-2 mbar: it has reduced. Very confusing… |
| 0535 | Pressure in IVC 4.6E-3 mbar, helium leak rate 2.2E-5 mbar l/s and falling. Fill main bath with helium gas. Pressure in IVC rises to 2.2E-2 mbar, as does helium leak rate to 3.6E-2 mbar l/s and rising. Looks like we have a huge leak, and this is the end of our adventure. |
| 0600 | Start 1-hour regeneration cycle on leak checker to remove helium contamination. |
| 1050 | Restart cryocleaning mixture. |