2021/04/20 (Tuesday)

Lab in-person: Matt
Virtual partner: Zach

Status	Run 74 in progress. Warming to fix IVC leak. Helium gas in cryostat vacuum jacket. Mixture in dump. Recovery valve open.
0705	MC(Cernox)/Sorb = 118/250 K
1105	MC(Cernox) = 141 K, rising at 5.4 K/hour. Suggests tau_warming of 28.6 hours, predicted to reach dew point Thursday night at 19:50.
1105	IVC = 300 mbar on digital gauge. Could be overpressurized now, need to go in and check.
1335	Matt enters lab
1335	MC(Cernox) = 153.9 K
1335	IVC = 300 mbar on digital gauge. Check pressure on mechanical gauge: a little less than 1 atm, maybe 0.95 bar. Good, still not overpressured.
1335	Pump out IVC gently with Scroll pump for 5 minutes, down to about 0.3 bar. Notice that this flattens out the temperature, apparently a cooling effect from pumping the IVC.
1340	Matt exits lab
1455	Matt enters lab
1455	Start gently pumping out IVC with Scroll Pump again this has a cooling effect, temperature stops rising, flattens out.
1505	Scroll on IVC = 0.1 mbar, and falling. So it looks like it's pumping out better now. Probably the leak has disappeared now that the IVC is warmer.
1510	Scroll on IVC = 7.4 μbar. Switch to Turbo Pump.
1510	Recovery meter = 0.08 cuft/hr.
1515	Turbo on IVC = 0.12 μbar. With Turbo valved out for 1 minute, IVC = 1.2 μbar. Continue turbo pumping.
1515	MC(Cernox) = 158.3 K
1530	Close helium recovery valve at MB exhaust.
1535	Try leak detector on IVC. With Turbo valved out for 1 minute, IVC leak signal = 510 pbarL/s. That's significantly lower than the signal seen during the LN2 blowout, maybe just because the temperature is higher.
1545	Turbo on IVC = 54 nbar. With Turbo valved out for 1 minute, IVC = 860 nbar
1600	Fill IVC slowly with N2 to around 0.46 bar on mechanical gauge. Note: digital gauge reads 190 mbar, I guess it just is not correct at highish pressures. MC temperature starts rising again
1605	Matt exits lab

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