2019/03/08 (Friday)

Previous Day

Status:	Start cooling to base yesterday. Still and Coldplate temperatures somewhat higher than usual. Tower cooldown is very slow.
0900	Tower/MC/Coldplate = 67.0/32.0/199 mK, Still = 1.76±0.02 K / 0.170 mbar, G1/G2 = 101/102 mbar, 1K Pot = 1.86 K / 45 mbar. MB = 24.3%
	Tower temperature is falling steadily at 5.7 mK/day. At this rate on Monday morning it will be 50 mK.
0910	Fill LN2 cold trap bath
1000	Begin LHe transfer @ MB = 22.3%
	Transfer caused spike in Tower temperature and various changes: circulation and still pressures are lower, 1K Pot temperature and pressure are lower. After the spikes, Tower temperature seems below its overnight trend and may be cooling more quickly.
1040	End LHe transfer @ MB = 91.8%
1110	Tower/MC/Coldplate = 66.0/30.9/190 mK, Still = 1.74±0.06 K / 0.150 mbar, G1/G2 = 90/92 mbar, 1K Pot = 1.78 K / 22 mbar. note that MC and Coldplate have also improved. Coldplate is closer to last run's temperatures.
1350	Tower = 65.3 mK, Still = 0.150 mbar, G1/G2 = 90/92 mbar, 1K Pot = 1.77 K / 20 mbar.
	Looks like the Tower cooling rate is now 6.3 mK/day. Really more like 6.0±0.5 mK/day, so maybe faster than before the transfer but maybe the same.
	Let's experiment with Still heating:
1400	Apply 1.0 mW to Still Heater small increases in circulation pressure and Still pressure. A little spike in Tower temperature then further cooling.
1420	Tower = 65.3 mK, Still = 0.160 mbar, G1/G2 = 92/95 mbar, 1K Pot = 1.78 K / 20 mbar.
1530	Tower/MC/Coldplate = 65.2/31.4/191 mK, Still = 1.70±0.06 K / 0.170 mbar, G1/G2 = 93/96 mbar, 1K Pot = 1.78 K / 20 mbar.
	The Tower temperature looks like it's no longer falling - it's been completely flat for the last hour. So let's turn the Still heater off again.
1535	Turn off Still Heater This caused a drop in Tower temperature then a bounceback - looks like the inverse of the spike that happened when we turned on the still heater.
1605	Fill LN2 cold trap bath
1620	MB = 86.6%

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