2017/06/28 (Wednesday)

Previous Day

Status	Transferred LN2 yesterday, but found a blockage when attempting throughput test. Need to blow out LN2 today.
0850	Lab = 22.6 C, 42% humidity (rainy today)
0855	MC(Cernox) = 78.3 K, Sorb = 124.3 K. DIB4 QETA to Chassis = 707 kΩ.
0855	Turbo (pumping on IVC) = 7.4 nbar. IVC 250 nbar
0940	LD on IVC = 120 pbarL/s
0945	Begin blowing out LN2 from main bath
0955	Attempt forward throughput test. Let the mixture in the pump outlet (at G2) into Trap 1 (leaving the rest in the dump). Open the condenser and still valves, then let mixture into condenser. No increase in still pressure = no throughput.
1005	Completed 77K electrical checks. Were surprised to find that all Qbias→QET connections are open (<1nS). This should be measuring the R_B through the crystal. Indeed in the last izip run (G106a) this measurement still gave 20nS at 77K. However, it seems unlikely that we managed to break wire bonds on all 4 charge channels at once. Perhaps this detector has improved blocking layers for the charge lines or something? The other interesting find involved phonon leakages to chassis. All side 1 channels seem to be ~2 nS to chassis. Side 2 PA,PB (outer ring and inner ring segment near DIB1) have ~80Ω to chassis while side 2 PC,PD,PE,PF have ~1MΩ to chassis. It seems like S2 PA/PB are pretty much shorted directly to ground, and the other channels see ground through the crystal and via S2 PA/PB.
	Also looked at cross-channels resistances. The tables below show channels on opposite faces measure ~1nS through the crystal while those on the same face are separated by ~1MΩ

DIB 1	77 K
	PA	PB	PC
PB	1.3 MΩ
PC	2.1 MΩ	750 kΩ
PD	1.5 nS	1.5 nS	1.4 nS

DIB 3	77 K
	PA	PB	PC
PB	1.5 MΩ
PC	1.6 nS	1.4 nS
PD	1.2 nS	1.0 nS	6.0 MΩ

DIB 4	77 K
	PA	PB	PC
PB	530 kΩ
PC	1.5 MΩ	0.9 MΩ
PD	1.1 nS	1.2 nS	1.2 nS

1000	LD signal suddenly rises, to >2000 pbarL/s. Is this a leak near the bottom of the IVC? It seems like it happened pretty late, when the blowout was maybe already finished. In that case it could be He blowing into the lab and hitting the top of the stripline tube. Not sure.
1005	LD signal has reached 400 pbarL/s, leveling off
1020	Begin pumping out main bath with scroll pump.
	LD signal did not decrease when we started pumping out the MB (instead it's higher). If it was a leak in the bottom indium seal you may have expected the signal to fall at this point.
1030	Main bath (P2) is less than 1 mbar so it looks like all the LN2 is out. Stop pumping MB and backfill it with helium.
	It looks like maybe the leak signal did fall while pumping out the main bath - then while backfilling it increased a lot, to 29000 pbarL/s. So maybe there is a leak in one of the indium seals of the IVC. Another theory is that helium comes out at the top somewhere, maybe the stripline tube -to- main bath seal, then gets into the IVC through that tube.
1045	Let 1.2 mbar He exchange gas into IVC
1050	Let two long hose-lengths of He into cryostat vacuum jacket.
1055	At this point I've been pumping out the fridge lines for a while. Yesterday we did the throughput test through Trap 2. Today's test was through Trap 1. If there was somehow a lot of contamination in the fridge lines, it could show up in either/both of the traps now. We'll warm up Trap 2 to see, and for now do a cleaning through Trap 1.
1100	Remove Trap 2 from LN2 bath to let it warm up
1110	Start cryocleaning mixture through Trap 1. V6 at 13.2%. After a few minutes flow stops, increase V6 to 13.4%
	MC and Sorb are warming. Cryostat surface is cool to the touch. Taped the thermometer probe to the outside of the cryostat.
1110	MC(Cernox) = 78.8 K, Sorb = 135.4 K, Cryostat surface = 18.9 C, IVC = 1.4 mbar
1130	MC(Cernox) = 80.8 K, Sorb = 150.3 K, Cryostat surface = 17.2 C, IVC = 1.6 mbar
1150	Cryocleaning flow stopped, increase V6 to 13.6%. Later I noticed that this was probably too much, G2 rose over 900. Eventually it came down a bit. The line out of the cold trap got quite frosty.
1200	MC(Cernox) = 86.5 K, Sorb = 177.0 K, Cryostat surface = 16.3 C, IVC = 1.6 mbar
1240	Stop cryocleaning after 90 minutes.
1245	MC(Cernox) = 98.5 K, Sorb = 215.8 K, Cryostat surface = 16.5 C, IVC = 1.9 mbar
1255	Open Trap 2 (now close to room temperature) up to G1. About 7.6 mbar of contaminants, not very much.
1345	MC(Cernox) = 116.2 K, Sorb > 249.9 K (max), Cryostat surface = 16.8 C, IVC = 2.2 mbar
1425	MC(Cernox) = 129.2 K, Cryostat surface = 11.1 C, IVC = 2.5 mbar
1440	Try a throughput test @ 130 K, using Trap 2, same procedure as yesterday except never opened V9, so using a smaller amount of mixture, whatever was left in the pump. G1 reaches maximum of 220 mbar before isolating mix in still, then falls to minimum of 12 mbar after opening G1 to condenser. Again, no throughput. Throughput < 0.1 mbar/min.
1507	Open Trap 1 (now close to room temperature) up to G1. About 2.3 mbar of contaminants, not very much.
1620	MC(Cernox) = 161.6 K, Cryostat surface = 18.2 C, IVC = 3.0 mbar
1640	Using Newton's Law of Cooling (or warming) the current trend suggests MC will hit freezing (273 K) at 8:05 in the morning.

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