2018/04/06 (Friday)

Previous Day

	Status: Warming fridge. All mixture in dump. 1K Pot needle valve open. Pumping out cryostat vacuum jacket overnight. Fridge and LN2 traps pumped out. IVC full of N2.
0000	MC(Cernox) = 273.1 K.
0400	MC(Cernox) = 274.1 K.
1005	MC(Cernox) = 275.2 K.
	Warming time constant climbed to 60 hours, 90 hours, 120 hours as vacuum jacket was pumped out.
1005	Turbo pump = 8.6 nbar. Cryostat vacuum jacket = 160 nbar with pump valved out. Close vacuum jacket valve.
1100	Check pressures in LN2 Traps 1/2: 2.2/1.2 mbar. These were pumped out yesterday so this was a check of how much leaks into them overnight if they are isolated. Not much - not enough to account for the overnight rise in contaminants we saw during cryocleaning, with the dump open to (either) cold trap overnight. So if there's a leak in from the outside, it's probably in the connections between the dump and IGH or 3He pump and IGH. Yesterday I tightened all the accessible clamps at the dump, pump, and their IGH ports that had some give.
1140	Start cryocleaning mixture through cold LN2 Trap 1. V6 = 12.2% (strangely low).
1145	Increase V6→12.8% to restart flow
1155	Increase V6→12.9% to restart flow
1210	Increase V6→13.0% to accelerate flow
1250	Stop cryocleaning, 70 min through Trap 1. Pump mixture to dump.
1245	Close 1K Pot needle valve
1255	Lower main bath, erect clean tent
1315	Start cryocleaning mixture through cold LN2 Trap 2. V6 = 12.8%
1320	Increase V6→13.1% to restart flow
1350	Increase V6→13.2% to restart flow
1425	Stop cryocleaning, 70 min through Trap 2. Pump mixture to dump.
1445	Check pressure in warm LN2 Trap 1: 9.5 mbar. Seems to be stable with time (maybe falling a little) so trap is I think completely warm. Pump out with scroll pump.
1500	Deinstalling tower. At this point, just starting to remove 100mK stage
1520	100mK stage removed. Ready to remove tower.
1520	Start cryocleaning mixture through cold LN2 Trap 1. V6 = 13.1%
1525	Increase V6→13.2% to restart flow
1550	Increase V6→13.3% to restart flow
1600	Modify SQUET ZC-24 with wirebonder. Now SQUIDs C and D have 6.7 mΩ shunts. This is meant to be a replacement for ZC-31 for use on DIB4 of the HV detectors. We had a suspicion that the ZC-31 SQUIDs were damaged during Run 66 (although bench checks show no problems).
1615	Perform electrical check on ZC-24, looks good
1615	Increase V6→13.4% to restart flow
1630	Stop cryocleaning, 70 min through Trap 1. Pump mixture to dump.
1645	Check pressure in warm LN2 Trap 2: 6.6 mbar. Pump out with scroll pump.
1655	Open dump to cold LN2 Trap 2 through V4 and V12b+speedivalve. Note this bypasses the pump which I'm leaving isolated.

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