2018/04/05 (Thursday)

Previous Day

	Status: Warming fridge. All mixture in dump. 1K Pot needle valve open. He and N2 gas in cryostat vacuum jacket. Fridge and LN2 traps pumped out. IVC full of N2.
0900	MC(Cernox) = 246.3 K
0950	MC(Cernox) = 248.8 K, Main bath outer surface = 21.5 C.
	Warming time constant has increased to 16 hours. It won't reach 273 K until 9:30 tonight at this rate.
0955	IVC = 0.55 bar
1000	Start pumping out IVC with scroll pump. We'll put warm N2 in, see if that warms it more.
1010	Let about 0.8 bar N2 into IVC (over about 15 minutes)
	pumping out the IVC caused a temporary slowing in the warmup. Letting N2 in sped it up again. As of 10:45 it looks like it has returned to what it would have been had we done nothing. Maybe the rate of warming increased a little.
1045	MC(Cernox) = 251.6 K, Main bath outer surface = 21.7 C.
1230	MC(Cernox) = 256.8 K, Main bath outer surface = 21.9 C.
1340	MC(Cernox) = 259.8 K, Main bath outer surface = 21.7 C.
1340	Let 100 mbar N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 14 mbar Let 100 mbar N2 gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 19 mbar
1345	Empirically it looks like one hose-length corresponds to 10 mbar in the vacuum manifold. Let another 20 hose-lengths into the cryostat vacuum jacket one at a time. This is the equivalent of 200 mbar N2 gas in the vacuum manifold. (But I let it directly into the vacuum jacket.) Vacuum jacket → 25 mbar.
1410	MC(Cernox) = 261.0 K, Main bath outer surface = 21.7 C.
1455	MC(Cernox) = 262.8 K, Main bath outer surface = 21.9 C.
	Adding the extra gas into the vacuum jacket doesn't seem to have increased the rate of warming. The time constant has been around 14-15 hours all day.
1657	MC(Cernox) = 267.1 K, Main bath outer surface = 22.1 C.
1713	MC(Cernox) = 266.2 K (on bridge display - previous measurements are from LabVIEW readout), Main bath outer surface = 22.7 C.
1714	Start pumping on vacuum jacket with scroll pump.
1733	Begin pumping on vacuum jacket with turbo pump when pressure reached 6.3E-2 mbar, turn off and close scroll pump.
2020	MC(Cernox) = 271.6 K. The warming continued at about the same rate for about an hour after pumping out the vacuum jacket.

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