2017/11/03 (Friday)

Previous Day

	Setup: DIB 1/3/4 → 3.2 MHz filters 1/2/3 → cable 1/3/2 → gender changers → rerouting boards 1/3/4 → DCRC33(2)/DCRC55(1)/DCRC50(3)
	Status: stopped circulation and 1K Pot yesterday. Both sides of fridge open to dump. 1K Pot needle valve left open.
0945	Tower = 2.18 K, rising overnight. 1K Pot > 7 K (off scale). Sorb = 12.5 K. G1/G2 (fridge+Trap1) = 206/176 mbar, rising overnight.
0950	Fill LN2 cold trap bath
0950	Close 1K Pot needle valve, isolating pot with He gas inside.
1000	Pump Trap 1 contents to dump
1025	Finish pumping Trap 1 to dump. Dump = 234 mbar. Remove Traps 1 and 2 from LN2 bath to let them warm up.
1030	Open fridge lines to G1, but keep isolated from dump.
1030	Tower/MC(Cernox) = 2.29/2.29 K. G1(fridge) = 147 mbar.
1035	Turn on MC heater and Still heater to 20 mW each. MC temperature and Fridge pressure begin rising.
1040	MC(Cernox) = 2.95 K. G1(fridge) = 282 mbar. Both rising steadily.
1055	MC(Cernox) = 3.67 K. G1(fridge) = 680 mbar. Both still rising. Sorb = 5.7 K - it has been falling since 10:35 when the heaters were turned on (and mixture was boiling off).
1055	Open V4 for a minute to let some fridge mixture into the dump, relieving the pressure. This causes the MC temperature to drop, 3.8→3.4 K. Then it starts rising again at same rate. Fridge pressure reduced to 420 mbar, then starts rising at previous rate.
1100	MC(Cernox) = 3.50 K. G1(fridge) = 550 mbar. Sorb = 6.1 K.
1110	Open V4 for a minute to let some fridge mixture into the dump, relieving the pressure. This causes the MC temperature to drop, 3.80→3.43 K. Then it starts rising again at same rate. Fridge pressure reduced to 460 mbar, then starts rising at previous rate.
1125	Open V4 for a minute to let some fridge mixture into the dump, relieving the pressure. This causes the MC temperature to drop, 3.84→3.56 K. Then it starts rising again at same rate. Fridge pressure reduced to 536 mbar, then starts rising at previous rate.
1148	Open V4 for a minute to let some fridge mixture into the dump, relieving the pressure. This causes the MC temperature to drop, 6.94→6.85 K. Then it starts rising again at same rate. Fridge pressure reduced to 590 mbar, then starts rising at previous rate.
1215	MC(Cernox) = 7.56 K. G1(fridge) = 675 mbar. Sorb = 14.6 K. MC and Fridge are flattening out.
1215	Start pumping fridge to dump, V6 = 13.0%. MC temperature falls a little.
1220	MC(Cernox)/Sorb = 7.49/15.5 K. G1(fridge) = 117 mbar. G2(dump) = 686 mbar. Increase V6 → 13.5%.
1225	Turn off MC and Still heaters. MC temperature falls.
1225	MC(Cernox)/Sorb = 7.27/15.9 K. G1/P1(fridge) = 0.5/0.22 mbar. G2(dump) = 717 mbar. Increase V6 → 100%.
1230	IVC = 54 nbar, up from 30 nbar yesterday when at base.
1230	MC(Cernox)/Sorb = 6.91/16.2 K. Fridge pressure approaching zero. G2(dump) = 719 mbar.
1230	Let 1 hose-length of He into IVC. MC temperature falls quickly, presumably approaching 4K bath temperature. Sorb falls too.
1235	Stop MIDAS programs and disconnect power from DCRCs.
1235	MC(Cernox)/Sorb = 5.26/10.7 K, flattening. G2(dump) = 719.5 mbar.
1300	MC(Cernox)/Sorb = 5.29/11.0 K. G2(dump) = 721.2 mbar, still creeping up but doesn't look like it would go much abot 722 mbar. G1/P1(fridge) = 0.4/0.030 mbar.
1300	Stop pumping mixture out of fridge. Isolate fridge, close IGH valves. Turn off 3He pump.
1310	Check port at top of main bath - still significant pressure, so there's still probably some LHe in there.
1315	Let 3“ hose-length of He into cryostat vacuum jacket. Recovery meter starts moving quickly. MC and Sorb temperatures rise.
1320	He recovery = 1 cuft/8 sec.
1320	MC(Cernox)/Sorb = 5.68/14.8 K
1335	MC(Cernox)/Sorb = 9.25/21.1 K. He recovery = 1 cuft/13 sec.
1335	MC(Cernox)/Sorb = 9.25/21.1 K. He recovery = 1 cuft/13 sec.
1340	MC warming rate suddenly increases.
1435	MC(Cernox)/Sorb = 42.0/66.6 K. He recovery very slow or stopped.
1610	MC(Cernox)/Sorb = 62.0/110.4 K.
1710	MC(Cernox)/Sorb = 73.9/136.0 K.
	by Newton's Law of Warming with Tlab = 22.8 C, the MC is warming with tau=19.3 hours and will hit Tdewpoint = 0.0 C around Sunday 4 Nov at 13:00.
	note temperature is currently being logged to I:\K100\temperature_20171020.txt
2135	MC(Cernox) = 118.5 mK. Warming is slowing down a little, tau=19.7 hours. Now predict Tdewpoint = Sunday at 14:00.
	or, if you allow for a quadratic term in logΔT versus t, Tdewpoint should occur Sunday evening at 19:19.

SQUET modifications

	Starting yesterday we began assessing some of our spare SQUETs. See the cold hardware page. We want to reduce the shunt resistances for the next run, a re-run of the Ge HV prototype, G101c(HV#2). The plan is to wirebond the 10 mΩ resistor in the SQUID card in parallel with the standard 20 mΩ resistor for a shunt resistance of 6.7 mΩ.
1400	Disassemble plate from ZC-23, a damaged SQUET - because from prior experience I know that it's difficult to handle the SQUET without breaking some wirebonds.
1430	Secure open SQUID card in vise. First remove flyover cable brace (2 long screws), then remove cover plate (2 short screws). Screw cover plate onto back of bare SQUID card with two short screws, not too tight - this will squish the wires somewhat. Then tighten SQUID card in vise bare side up and level with top. Then tie down the larger FET card onto the vise so it doesn't get in the way.


Bare SQUID card with plate on back in vise	FET card tied down to side of vise

1610	Finish wirebonding 10 mΩ resistors in parallel with 20 mΩ resistors on all four phonon channels of ZC-23. Used standard wirebonder settings: power = 300/300, time = 30/30, height = 50, drop = 10, but later increased power to 330 to get bonds to stick more reliably. Did two bonds on each connection, mimicking the previous bonding. Noticed some left over bond ends where I was bonding, suggesting that this SQUET had at one time its 10 mΩ resistors connected.

1610

Finish wirebonding 10 mΩ resistors in parallel with 20 mΩ resistors on all four phonon channels of ZC-23. Used standard wirebonder settings: power = 300/300, time = 30/30, height = 50, drop = 10, but later increased power to 330 to get bonds to stick more reliably. Did two bonds on each connection, mimicking the previous bonding. Noticed some left over bond ends where I was bonding, suggesting that this SQUET had at one time its 10 mΩ resistors connected.


15:39:37	15:52:10	15:52:16	15:57:18


15:58:41	15:59:50	15:59:58	16:00:32

1650	Reassemble SQUET ZC-23
1705	Finish wiring check of ZC-23. Nothing extra broken - SQUID A is open as before but everything else OK.

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