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2019/09/21 (Saturday)

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Status: LN2 transfer yesterday. Circulated mixture through fridge continuously during transfer. Left it with condenser side open to mixture and cold LN2 Trap 2 and dump and 3He pump, pump off.
0200 MC(Cernox) flattens out around 77 K
Sorb very slowly increasing overnight, from 116.3 K to 116.7 K
0950 MC(Cernox)/Sorb = 77.27/116.7 K
1450 Top off LN2 cold trap from small dewar. Refill small dewar.
1452 MC(Cernox)/Sorb = 77.26/116.9 K
1455 Prepare for throughput test. Turn on 3He pump, close V12B + speedivalve, and open V3 and V5 to pump out fridge lines from both sides to dump.
1508 G1/P1 = 2.1/1.6 mbar, Close V1 and V5
Throughput test procedure, Cold Trap 2:
  1. All mixture in dump, LN2 trap 2 cold, condenser & still valves open (3He pump on - optional)
  2. Open V9, V13b, V12b+speedivalve, V3. Wait for G1 to be close to G2.
  3. Close V12a+speedivalve and V3, open V1
  4. monitor G1
1512 Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 572 mbar before Step 3, then it falls to 63 mbar, then rises. Throughput = 45.9 mbar/min. [image not archived: cool.svg] A little higher than last time, 2019 May 24
1515 Open V12B + speedivalve and V3. Turn off 3He pump. So we have V9, V13B, V12B + speedivalve, V1, and V3 open. This opens the dump to both sides of the fridge via cold trap 1.
1528 77K electrical check shows DIB3 Feedback Coil A = 1.4MΩ. That sucks, this is Side2 PB, the channel the source will move across.
Also: DIB2 QI: GND → DIB2 QI FB/Drain/Source = 16/64/64 nS and DIB2 QI FB/Drain/Source → GND = 16/<1/<1 nS. Looks like some kind of short there. Slightly high conductance to GND on most channels. SQUID channels ~1.5 nS, QET bias/ret ~ 8 nS.
1720 MC(Cernox)/Sorb = 77.25/116.9 K

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