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2012/09/19

0025 Fill N2 cold trap full.
Start cryocleaning mixture through nitrogen cold trap 2.
1020 Cleaned Cricket's bowl.
1030 Fed Cricket 3 pellets.
1040 Filled LN2 cold trap.
1050 Turn on scroll pump. Begin evacuating N2 exchange gas. Mixing chamber: 78.6 K.
Opened turbo pump, then isolated scroll pump when pressure read 3E-2 mbar.
1530 Fed Cricket 4 pellets.
1705 Background helium leak rate 9.8E-10 mbar l/s. Start blowing nitrogen out of main bath.
1845 Nitrogen is out of main bath. Helium leak rate jumped to around 1E-6 mbar l/s, and then started increasing slowly. It is currently at 1.2E-5 mbar l/s. It would appear as though there is a leak in the bottom flange. Will confirm once rubber hose has gone limp and main bath has been sealed off and evacuated.
1850 Evacuate main bath. Helium leak rate has increased to 1.5E-5 mbar l/s and is holding steady.
1935 Helium leak rate has fallen to 5.2E-8 mbar l/s. Stop evacuating main bath and overpressurise with helium gas. Helium leak rate rises to 1.7E-4 mbar l/s.
2240 IVC pressure has risen to 0.022 mbar. Remove helium recovery hose and attach ping-pong ball to prevent overpressurisation of main bath during warm up. Open valve to turbo pump to evacuate IVC for a few seconds. Isolate turbo pump.