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2018/05/25 (Friday)

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Status: Initial LHe transfer yesterday. Somewhat modified procedure for treating 1K Pot.
0820 MC(Cernox)/1K pot/Sorb = 4.66/6.22/8.0 K, Turbo on IVC = 1.9 nbar, G1(fridge) = 541 mbar, MB=76.0%
0825 Fill LN2 cold trap bath
0835 Check pressure in 1K Pot: 8/30 bar on mechanical gauge. Opening the speedivalve causes a dip in pot temperature, 6.3→4.6 K then back up. (Sorb also dips, to 6 K)
0835 Pump out 1K Pot with scroll pump. Another temperature dip, 5.7→4.8 K then back up. (Sorb also dips, to 6 K)
0845 1K Pot = 0.20 mbar, reasonably flat. Stop pumping on pot, see how quickly pressure rises:
minutes mbar (P2)
0 0.2
0.5 1.2
1.0 2.6
2.0 4.5
3.0 6.0
4.0 8.0
this is much slower than May 16, that's good
1000 Open 1K Pot needle valve about 30 degrees. 1K Pot: 6.5 K / 0.09 mbar → 3.0 K / 7.5 mbar
1005 Open 1K Pot needle valve about 10 degrees more. 1K Pot: 2.9 K / 7.5 mbar → 2.5 K / 18 mbar
MC(Cernox) has fallen from 4.6 to 3.3 K. G1(fridge) has fallen from 540 to 430 mbar.
1010 Open 1K Pot needle valve about 10 degrees more. 1K Pot: 2.5 K / 18 mbar → 2.1 K / 32 mbar
1020 Tower = 2.97 K and falling, G1(Fridge) = 293 mbar and falling
1020 Open 1K Pot needle valve about 10 degrees more. 1K Pot: 2.1 K / 32 mbar → 1.7 K / 130 mbar. After a few minutes pressure falls.
1030 Tower = 2.54 K, G1(Fridge) = 152 mbar, 1K Pot = 1.69 K / 55 mbar
1040 Tower = 2.15 K, G1(Fridge) = 72 mbar, 1K Pot = 1.61 K / 20 mbar
1040 Open 1K Pot needle valve about 10 degrees more. 1K Pot → 1.63 K / 28 mbar.
1045 Tower = 2.10 K, G1(Fridge) = 63 mbar, 1K Pot = 1.62 K / 25 mbar … then 1K Pot pressure rises off-scale, 1.77 K. Maybe we hit the lambda point. Fridge and tower had flattened out at this point.
1050 1K Pot = 1.77 K / 1.3/30 bar (off-scale on P2)
1055 Pot pressure still off-scale, tower and fridge flat. Try closing needle valve a little.
1100 Close 1K Pot needle valve about 10 degrees less. 1K Pot → 1.75 K / 1.3/30 bar.
1105 Close 1K Pot needle valve about 10 degrees less. 1K Pot → 1.70 K / 120 mbar.
1110 1K Pot = 1.71 K / 140±20 mbar (oscillating)
1115 Close needle valve, then switch from scroll pump to 4He pump. Open 4He exhaust to recovery (both valves)
1120 With needle valve still closed, 1K Pot → 1.37 K / 1.7 mbar, and Tower and Fridge start falling. Leave it like this for a bit.
1125 Tower = 1.98↓ K, G1(Fridge) = 54↓ mbar, 1K Pot = 1.42 K / 3.5 mbar
1130 Tower = 1.83↓ K, G1(Fridge) = 46↓ mbar, 1K Pot = 1.36 K / 1.6 mbar
there was a brief increase in the pot pressure&temperature, and the fall of the fridge and tower accelerated. Let's try opening the needle valve a little.
1135 Open 1K Pot needle valve 20 degrees. 1K Pot: 1.36 K / 1.5 mbar → 1.42 K / 3.2 mbar
1140 Tower = 1.75↓ K, G1(Fridge) = 40↓ mbar, 1K Pot = 1.42 K / 3.2 mbar. Tower/Fridge cooling slowing down.
1155 Tower = 1.69↓ K, G1(Fridge) = 35↓ mbar, 1K Pot = 1.48±0.02 K / 5±1 mbar.
1215 Tower = 1.66 K, G1(Fridge) = 32 mbar, 1K Pot = 1.48±0.02 K / 5±1 mbar. Flattening out, will start circulation soon
1240 Tower = 1.65 K, G1(Fridge) = 30 mbar, 1K Pot = 1.48±0.01 K / 5.0±0.5 mbar.
1240 Open 1K Pot needle valve 10 degrees more. 1K Pot → 1.54±0.02 K / 10±2 mbar
1245 Close V9 leaving 36.9 mbar in dump. Close V3. Turn on 3He pump, which will push a little more mix into condenser. Fridge pressures rise a little.
1250 Start circulation through Trap 1. V6 → 12.8%. Condenser peaks at 90 mbar. Slight 1K Pot pressure spike to 20 mbar, then falls. Tower falls to 1.45 K.
1300 V6 → 13.2%. Condenser peaks at 90 mbar. Tower → 1.41 K. P1 falls into range.
1305 V6 → 13.5%. Condenser peaks at 105 mbar. Tower → 1.23 K. Still → 8 mbar.
1310 V6 → 13.8%. Condenser peaks at 90 mbar. Tower → 1.04 K. Still → 4.5 mbar.
1315 V6 → 14.2%. Condenser peaks at 100 mbar. Tower → 0.86 K. Still → 2.8 mbar.
1320 Tower/MC(H35)/Coldplate/Still = 0.84/0.80/0.76/1.23 K
1325 V6 → 15.0%. Condenser peaks at 100 mbar. Tower → 0.44 K. Still → 0.95 mbar.
1330 V6 → 100%. Condenser peaks at 100 mbar. Tower → 0.16 K. Still → 0.20 mbar.
1345 Tower/MC/Coldplate = 80.0/59.1/188 mK, Still = 1.15 K / 0.120 mbar, G1/G2 = 69/86 mbar, 1K Pot = 1.54 K / 8 mbar.
1350 Open V14 to let the rest of the mixture from the trap into circulation. Condenser peaks at 80 mbar, Still peaks at 20 mbar, MC rises to 73 mK and plateaus, starts falling again after a couple of minutes.
1400 Tower = 59.3 mK, Still = 3.6 mbar, G1/G2 = 55/75 mbar, 1K Pot = 1.54 K / 8 mbar.
1410 Tower = 58.0 mK, Still = 1.0 mbar, G1/G2 = 58/73 mbar, 1K Pot = 1.54 K / 8.5 mbar.
1420 Tower = 55.0 mK, Still = 0.55 mbar, G1/G2 = 60/75 mbar, 1K Pot = 1.53 K / 7.5 mbar.
1420 Close V14
1500 Tower/MC/Coldplate = 53.1/32.6/183 mK, Still = 1.19 K / 0.110 mbar, G1/G2 = 61/77 mbar, 1K Pot = 1.54 K / 8 mbar.
Tower temperature has flattened out at 53 mK
1505 Try setting Still heater to 1 mW. Condenser rises a little, to 0.12 mbar; circulation pressures rise a little. No change in tower temperature.
1510 Try setting Still heater to 2 mW. Condenser → 0.14 mbar, G1/G2 → 66/84 mbar. Tower cools very slightly, 53.0→52.5 mK.
1520 Try setting Still heater to 4 mW. Condenser → 0.16 mbar, G1/G2 → 69/89 mbar. Tower peaks to 54 mK then cools a bit, →52.2 mK.
1525 MC = 31.7 mK
1600 Messed with still heater a little more, then turned it off.
1630 Tower/MC/Coldplate = 52.2/32.1/182 mK, Still = 1.23 K / 0.100 mbar, G1/G2 = 62/77 mbar, 1K Pot = 1.54 K / 8±0.5 mbar.
not cooling much now but maybe it will slowly go down over the weekend. It's a bit colder now than the first day of Run 62, and in that run it cooled to below 35 mK in a couple weeks.
1655 Fill LN2 cold trap bath
2100 Tower = 51.3 mK

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