2015/02/22

1335	At roughly 2300 last night, the mixing chamber thermometer reached a stable low point of 2.4 K. It had been cooling steadily from 32 K at roughly 2100 when the mixing chamber heater was unplugged. Thus it is likely that the mixing chamber heater was responsible for the high temperatures. Since that time, some mixture has been condensing, but the process is not completed. Currently mixing chamber temperature is 2.4 K, G1=90.6 mbar (cold trap 1 speedivalve closed), G2=315 mbar (V9 and V13A closed), P1=1000. Open coldtrap 1 speedivalve and V9 and V13A to continue circulation. Since 656 mbar was in G2 yesterday at the start of circulation, add 350 mbar to make G2 pressure 306 mbar.
1545	306 mbar left in dump. Close V9.
1550	Fill LN2 coldtrap full. Start circulating procedure. G1=72.3 mbar, G2=40.7 mbar, mixing chamber at 2.23 K.
1600	V6 opened fully. G1=119 mbar, G2=104 mbar, P1=0.22 mbar, P2=26 mbar. Mixing chamber at 1.06 K and dropping.
1602	Mixing chamber at 875 mK and has starting to climb.
1610	Mixing chamber temperature at 1.16 K and still rising. P1=90 ubar, G1=71.5 mbar, G2=52 mbar.
1621	Plug in 1K Pot, reads 1.612 K. Unplug 1K Pot. Mixing chamber temperature still oscillating.
1630	Mixing chamber temperature drops from 1.1K to ~700 mK.
1640	Mixing chamber temperature reaches 1.129 K, G1= 90 mbar, G2=65 mbar.
1648	Mixing chamber temperature at 820 mK.
1650	Mixing chamber temperature maxes out at 900 mK.
1651	Mixing chamber temperature reaches a minimum of 850 mK.
1658	Mixing chamber temperature maxes out at 1.1 K.
1659	Mixing chamber temperature reaches a minimum of 980 mK.
1702	Mixing chamber temperature maxes out at 1.05 K.
1704	Mixing chamber temperature reaches a minimum of 697 mK.
1706	Mixing chamber temperature maxes out at 890 mK.
1711	Mixing chamber temperature reaches a maximum of 1.01 mK. These oscillations continue, but they will no longer be recorded unless there is a significant change.
1754	Mixing chamber temperature at 930 mK. Plug in 1K Pot thermometer/ mixing chamber heater. Stop circulation and start collecting mix in the dump.

Mixing Chamber (H35) Temperature

1855	Mixing chamber temperature at 1.2 K, turn on mixing chamber heater. Start the leak checker and set to He-3 mode.
2220	Perform He-3 leak check with 1K Pt at 4.6 K and mixing chamber at 18 K. Although we do not have a way to absolutely calibrate a He-3 leak check, we are able to perform a relative calibration. We had a leak rate of 3.8E-8 mbarL/s when open to the line leading up to the IVC. This leak rate dropped to 3.6E-8 mbarL/s when we opened the leak checker to the IVC.
2240	Close gate valve and condenser line speedivalve.