2019/05/16 (Thursday)

Previous Day

Status	Blockage found yesterday, 4th attempt. Warming up. N2 in cryostat vacuum jacket and IVC.
Setup	DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2
	Some mixture has been sitting in the still side of the fridge overnight, waiting to see it leak through to the condenser side. The rest of the mixture is in the dump and cold LN2 Trap 1 with the 3He pump on. LN2 Trap 2 is clean, Trap 1 has been exposed to the mixture since yesterday's throughput test. Removed 9.0 mbar
0526	G1(Condenser) starts to rise linearly. Before this time it was flat. At this time MC(Cernox)/Sorb = 209.2/>249 K If we try to extrapolate the sorb temperature based on its warming trend yesterday, assuming it approaches room temperature, then it was within 1 C of room temperature (23 C) at this time. Throughput = 6.55 mbar/min @ MC(Cernox) = 209.2 K That's a little less but similar to the throughput at 228 K seen on May 2.
0805	MC(Cernox)/Sorb = 222.8/>249 K. G1(condenser) = 524 mbar and flattening out, looks like now it's equal to the Still side.
0855	Fill LN2 cold trap bath

some thoughts:

we could consider this temperature warm enough, since the blockage is gone. Should we go ahead and pump out the vacuum jacket and IVC?
we could just try to clean more, then try again.
- if so then we can try repeated throughput tests during the LN2 transfer, as the temperature is falling
it looks clear that Trap 1 is more efficient at cleaning than Trap 2.
- suggest alternating 2-hour and 1-hour cleanings with Trap 1 only, see if there's a difference

0925	Start pumping from Still side to dump (and Trap 1), V6 = 12.8%. This is a mini-throughput test, we can watch to see if the Condenser pressure falls. P1(Still) falls and G1(Condenser) starts falling too, showing througput at 4.8 mbar/min.
0950	Open V3 to pump both sides of fridge to dump. Open V6 further, >25%.
1125	Stop pumping mixture out of fridge, isolated fridge. Pump mixture out of LN2 Cold Trap 1 into dump.
1255	LN2 Trap 1 is warm. Check contents: 9.1-0.1 = 9.0 mbar on G1. Pump out with 4He pump.
1228	Start pumping on cryostat jacket with scroll pump. Jacket pressure = 7.4 mbar, MC(Cernox)= 241.7
1320	Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.4%
1330	Increase V6→12.7% to restart flow
1335	Start pumping cryostat vacuum jacket with turbo pump
1340	Increase V6→12.8% to restart flow.
1420	Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 580-750 mbar. Pump mixture to dump. Removed 5.7 mbar.
1520	LN2 Trap 1 is mostly warm. Check contents: 5.7-0.0 = 5.7 mbar on G1. Pump out with 4He pump.
1540	Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 13.2%
1640	Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 580-800 mbar. Pump mixture to dump. Removed 4.3 mbar.
1705	Take Trap 1 out to warm up. Top off LN2 cold trap.
1710	Set up passive cleaning with both sides of dump and pump contents exposed to Trap 2. With 3He pump on, open V9, V4, V12B+speedi, V13B.
1712	Turbo on cryostat vacuum jacket = 19 nbar. Close off pump for a few minutes: cryostat vacuum jacket = 220 nbar. Stop pumping out vacuum jacket, start pumping out IVC.

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