| 0015 | Close V8 to isolate mixture. Open V7 to vent. Open V2A & V5A to observe pressure on P2 and clear line for pumping with He-4 pump. |
| 0050 | Remove cold trap 1 from LN2 bath and subject it to a heat gun, spread uniformly, until surface just too hot to touch. P2 increases to 60 mbar. Switch on He-4 pump to pump it out. Wait for trap to return to room temperature. Close valves 2A, 7 & 11A to isolate He-4 pump. Place trap back in LN2 bath. Wait for trap temperature to reach 77 K. |
| 0130 | Fill cold trap full. |
| 0140 | Open valve 13A to cool charcoal. Liquid nitrogen bath boils vigourously for about a minute as expected. |
| | Start cryocleaning mixture through cold trap 1. |
| 0255 | Stop cryocleaning; pump mixture into dump. |
| 0330 | No improvement in throughput; pump mixture into dump. Time to clean the helium trap. |
| 0535 | No improvement in throughput; pump mixture into dump. A couple of strange things: |
| | 1. Helium cold trap seems to hit an obstruction on its way in. Cannot push it in completely. The bottom of the cold trap hits the liquid, but the top 15 cm or so remains outside of the main bath. No idea what is causing the obstruction. The only way to find out is to open the fridge and take a look. |
| | 2. Opening valve 13A causes G1 to jump to 600 mbar. This makes no sense, as there is no connection between this valve and gauge G1. Valve 12A was closed. This is repeatable. Additionally, the condenser line is taking longer to pump out than before: G1 never seems to hit 0, although it had no problem hitting zero before the helium trap was cleaned. What happened? |
| 0545 | Give up, go home, sleep for an hour… |
| 1200 | Slept for more than an hour. Spoke with Vuk; couple of things: |
| | 1. Helium cold trap is alright in its current position. There is probably a hole that doesn't quite line up. No need to open it up and have a look. |
| | 2. There is a leak in valve 12A. Charcoal from the cold trap might have made its way in there. This is a common problem. |
| | A poor throughput rate will result in a higher base temperature. However, it can be argued that this is only of significance for the phonon channels, and seeing as only the charge signals are important for the 100 mm crystal tests, we can get away with a higher base temperature. |
| | So, the plan is to proceed! |
| 1605 | Blow out LN2. |
| 1940 | LN2 out of main bath. He background leak level 1.4E-8 mbar l/s. No evidence of leak - leak rate actually falls to 1.2 E-8 mbar l/s. |
| | Remove transfer stick. Evacuate main bath (P2 = 0.065 mbar). Evacuate 1 K pot and add He-4 exchange gas to IVC at a pressure of 4.6E-2 mbar. |
| 2100 | Pump LHe transfer stick to 4.3E-3 mbar. |
| 2130 | Begin LHe transfer. |
| 2320 | Stop LHe transfer; main bath 90% full. |
| 2325 | Pump out exchange gas at MC temperature of 25 K. Leave to pump out overnight. |