2018/05/01 (Tuesday)

Previous Day

	LN2 transfer yesterday.
0845	MC(Cernox) = 77.3 K, Sorb = 128.6 K, IVC = 1.9 mbar, G1 (fridge) = 210 mbar
0845	Pump out IVC with scroll pump, then turbo pump
0855	Electrical checkout on DIB3: all ok. SQUID A is open, we knew about this; also Feedback D is reading too high (500 kΩ, s/b 8 kΩ). But neither A nor D are readout channels.
1036	Electrical checkout on DIBs 1,4: all phonon channels okay. A short to ground somewhere in DIB4QI between FET and feedback line.
1105	Turbo pressure 14 nbar; IVC with turbo valved out = 740 nbar; leak on IVC = 53 pbarL/s with turbo pumping, 390 pbarL/s with turbo valved out
1115	Start blowing out LN2
1115	IVC leak = 402 pbarL/s, Main bath = 389 mbar above 1 atm
1125	IVC leak = 399 pbarL/s, Main bath = 389 mbar above 1 atm
1135	IVC leak = 382 pbarL/s, Main bath = 385 mbar above 1 atm
1145	IVC leak = 1000 pbarL/s, Main bath = 140 mbar above 1 atm. Crap, looks like another leak into IVC.
1146	IVC leak = 2000 pbarL/s, Main bath = 138 mbar above 1 atm. Stop pressurizing main bath.
1147	IVC leak = 7000 pbarL/s
1150	IVC leak = 10,000 pbarL/s
1200	IVC leak = 11,200 pbarL/s, flat
1200	Start pumping main bath with scroll pump. LD goes down a little after pressure falls to 0.1 bar.
1205	IVC leak = 5000 pbarL/s, main bath = 0.05 bar
1210	IVC leak = 880 pbarL/s, main bath = 0.7 mbar
1215	IVC leak = 474 pbarL/s, main bath = 0.22 mbar
1230	IVC leak = 340 pbarL/s, main bath = 0.075 mbar (scroll pump pressure)
1235	Fill main bath with N2 gas
1250	IVC leak = 300 pbarL/s. Squirt a blast of He down the LN2 fill tube, with the tube raised above the funnel. Leak 300→305. Repeat with tube pushed all the way down: Leak 305-310. Huh - not seeing the IVC leak. Squirt a blast around the stripline elbow KF flange: Leak 350→400. What's going on here?
1300	Squirt-checks at top of fridge. Large leak at KF-flange on T-pipe, the side port that t's off to the pumping line. Leak 400→1200. Turns out the clamp was very loose. Tightened it, now the leak is gone.
1300	Start pumping the N2 out of the main bath with the scroll pump.
1305	Try Mini-throughput check: close off Trap 1 and V3. Only V1, condenser speedivalve, still gate valve, and V9 open. Turn on 3He pump, then open V6 to 12.8%. This pumps mix out of the still side and we can see if the pressure goes down on the condenser side. G1 (condenser) started out at 203 mbar, starts to fall, about 6 mbar/min
	Throughput test procedure, Cold Trap 1:

All mixture in dump, LN2 traps cold, condenser & still valves open (3He pump on - optional)
Open V9, V13a, V12a+speedivalve, V3. Wait for G1 to be close to G2.
Close V12a+speedivalve and V3, open V1
monitor G1

1315	Perform mixture throughput test at MC = 77 K using above procedure. Let G1 rise to 590 mbar before Step 3, then it falls to 85 mbar, then begins to rise. Throughput 46.6 mbar/min. Close to April 25.
1320	Main bath = 0.4 mbar. Now let's fill it with He, see if the leak changes. Leak = 250 pbarL/s.
1325	Let about 0.5 bar He into IVC - leak signal rises above 10,000 pbarL/s. Stop letting in He; let's pump it out again and test some more.
1325	Leak = 18,000 pbarL/s. Start pumping He out of main bath again
1340	Main bath = 0.55 mbar, Leak = 331 pbarL/s.
1340	Let 1 hose-length of He into main bath. Leak → 355 pbarL/s. after a couple minutes, Leak = 375 pbarL/s
1345	Let a blast of He into main bath. Leak → 600 pbarL/s. after a couple minutes, Leak = 875 pbarL/s
	well this definitely looks like an IVC leak. But why didn't we see it when we blasted He down the fill tube??
1350	Let a blast of He into main bath. Leak → 1100 pbarL/s. after a couple minutes, Leak = 875 pbarL/s
1405	Pump out main bath again, then fill with N2 again
1425	Main bath full of N2. IVC Leak = 225 pbarL/s. Try squirting blasts of He down the ports. Try the top port, then try the transfer tube at various heights, 15“ down to 1”, then try transfer tube pushed into funnel. For everything except tube-in-funnel, leak only increases by 1 pbarL/s at most. A blast down the tube with it pushed into the funnel causes a leak increase of 230→300 pbarL/s. A longer blast (count of 3) causes a 305→360 pbarL/s increase. These aren't huge. But it's clear that the leak is near the bottom of the bath. And the leak gets very large when you fill the bath with He. (Even when it's still well below 1atm, so it can't be a leak at the top from He leaking out of the bath).
1615	Try again with leak checks at top of fridge - no big leaks, maybe increases of +20 pbarL/s. Squirt down the fill line, extended blast; signal increase is maybe double this value.
1620	Pump out IVC again.
1640	Start letting He into IVC in bits.
	1 hose-length of He, Main bath 7→9.5 mbar, IVC leak 200 pbarL/s, no increase
	5 hose-length of He, Main bath →9.5 mbar, IVC leak → 400 pbarL/s
	more He, Main bath →2/30 bar, IVC leak → 2400 pbarL/s
	more He, Main bath →5/30 bar, IVC leak → 5000 pbarL/s
	more He, Main bath →15/30 bar, IVC leak → 15,000 pbarL/s
	more He, Main bath →338 mbar above 1 atm, IVC leak → 20,000 pbarL/s
	ok, just seems like too much. start warmup.
1650	MC(Cernox) = 77.5 K. Sorb = 142.8 K.
1700	Let N2 into the IVC up to about 0.21 bar. MC has climbed to 78.1 K
1715	Let 26 plastic-hose-lengths of N2 into cryostat vacuum jacket (equivalent of about 200 mbar at pump manifold). Vacuum jacket pressure = 10 mbar. Notice that main bath pressure increases.
1715	MC(Cernox) = 79.4 K, Sorb = 154.6 K
1715	Pump mixture to dump
1745	MC(Cernox) = 83.1 K, Sorb = 175.3 K
1745	Release main bath pressure to recovery

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