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2020/02/18 (Tuesday)

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Status LN2 transfer yesterday. Beginning Run 72 cooldown.
0920 MC(Cernox) = 77.3 K, Sorb = 118.8 K, IVC = 1.6 mbar, G2/G1 = 529/588 mbar
0925 Turn on 3He pump and open V6 to 12.8%, reestablishing circulation like yesterday. G2/G1/P1 → 650/718/2.2 and settle.
0925 Close V12a speedivalve for 2 minutes to assess throughput. G1 falls at 64 mbar/min, good.
Throughput test procedure, Cold Trap 1:
  1. All mixture in dump, LN2 trap 2 cold, condenser & still valves open (3He pump on - optional)
  2. Open V9, V13a, V12a+speedivalve, V3. Wait for G1 to be close to G2.
  3. Close V12a+speedivalve and V3, open V1
  4. monitor G1
0935 Perform mixture throughput test at MC = 77 K using above procedure with 3He pump on. Let G1 rise to 550 mbar before Step 3, then it falls to 70 mbar, then rises. Throughput = 43.5 mbar/min. A little lower than last time, 2019 NOv 5
0945 Pump out IVC with leak detector. This is maybe a little hard on the sensor, probably better to pump out with scroll pump, but I had the scroll pump backing the leak detector already so thought I'd try this to save time.
After a few minutes the leak detector beeps out an error, Amplifier Signal Too High, about the same time that IVC falls to 0.1 mbar so switch to turbo pump, close off LD and let it settle down.
1005 Perform electrical checks on all 3 DIBs.
77K electrical checkout
DIB4 + accessories The shorts to chassis seen yesterday have disappeared. But SQUID D reads too high, 17.4 kOhm, should be 3-5 kOhm. pD is used so this could be a problem.
DIB1 As seen before, SQUID and Feedback D are both open. This channel is not used so not a problem for this setup.
DIB3 All OK
1020 Turbo on IVC = 14 nbar. Leak signal on IVC with turbo pumping: 230 pbarL/s. With turbo valved out: 2200 pbarL/s. Switch back to pumping IVC with turbo.
1030 IVC = 1500 pbarL/s with Turbo valved out. Switch back to pumping it with Turbo a little longer.
1035 Turbo on IVC = 8.6 nbar
1050 IVC = 1630 pbarL/s with Turbo valved out, after settling for a few minutes
1100 Begin blowing out LN2. Main bath (G3) = 561 mbar above 1atm.
1100 IVC = 1480 pbarL/s, MB = 558 mbar+1atm
1110 IVC = 1360 pbarL/s, MB = 547 mbar+1atm
1120 IVC = 1280 pbarL/s, MB = 540 mbar+1atm
1130 IVC = 1220 pbarL/s, MB = 542 mbar+1atm
1131 G3 begins falling, IVC = 1210 pbarL/s, MB = 330 mbar+1atm
1140 IVC = 1310 pbarL/s, MB = 184 mbar+1atm and leveling out.
Stop pressurizing MB.
1145 IVC = 1180 pbarL/s, MB = 97 mbar+1atm
1150 Start pumping out main bath with scroll pump. Takes 12 minutes to fall to 1 mbar.
1205 Pressurize MB with helium to 324 mbar above 1 atm. Open 1K Pot speedivalve and needle valve (5 full turns) to repressurize pot as well. Close 1K Pot valves again.
1215 Let 63 μbar He exchange gas into IVC.
1220 MC(Cernox) = 77.5 K, Sorb = 126 K, IVC = 63 μbar, G1(fridge) = 609.2 mbar. G3(MB) = 324 mbar.
1235 Start initial LHe transfer
1245 MC(Cernox) = 78.1 K, Sorb = 130 K, IVC = 40 μbar, G1(fridge) = 608.2 mbar. G3(MB) = 486 mbar.
1255 MC(Cernox) = 74.6 K, Sorb = 114 K, IVC = 22 μbar, G1(fridge) = 596.3 mbar. G3(MB) = 428 mbar.
1305 MC(Cernox) = 65.2 K, Sorb = 81 K, IVC = 14 μbar, G1(fridge) = 553.0 mbar. G3(MB) = 491 mbar.
1310 Helium level meter starts to read 5.5%
1315 MC(Cernox) = 60.0 K, Sorb = 57 K, IVC = 12 μbar, G1(fridge) = 521.0 mbar. G3(MB) = 473 mbar. MB = 11.4%
1325 MC(Cernox) = 54.1 K, Sorb = 10 K, IVC = 12 μbar, G1(fridge) = 470.0 mbar. G3(MB) = 438 mbar. MB = 29.7%
1335 MC(Cernox) = 49.4 K, Sorb = 7.5 K, IVC = 8.6 μbar, G1(fridge) = 461.8 mbar. G3(MB) = 428 mbar. MB = 48.0%
1345 MC(Cernox) = 44.7 K, Sorb = 7.5 K, IVC = 8.6 μbar, G1(fridge) = 458.8 mbar. G3(MB) = 420 mbar. MB = 65.5%
1355 MC(Cernox) = 39.5 K, Sorb = 7.0 K, IVC = 8.6 μbar, G1(fridge) = 456.0 mbar. G3(MB) = 418 mbar. MB = 86.4%
1404 Ended LHe transfer at MB = 89.5%.
1410 MC(Cernox) = 31.3 K, Sorb = 6.5 K, IVC = 7.4 μbar, G1(fridge) = 497 mbar. G3(MB) = 180 mbar.
1420 Make sure that Range on LakeShore bridge is 2.00 kΩ, so that Cernox thermometer readout doesn't peg.
1430 MC(Cernox)/Sorb/1K Pot = 20.5/6.0/4.88 K, IVC = 6.3 μbar
1440 MC(Cernox)/Sorb/1K Pot = 16.5/5.8/4.72 K, IVC = 6.3 μbar
1450 MC(Cernox)/Sorb/1K Pot = 14.0/5.7/4.60 K, IVC = 4.0 μbar
1455 MC(Cernox)/Sorb/1K Pot = 12.9/5.6/4.57 K, IVC = 4.0 μbar
1500 MC(Cernox)/Sorb/1K Pot = 11.8 K, IVC = 3.4 μbar
1505 MC(Cernox)/Sorb/1K Pot = 10.5/5.5/4.49 K, IVC = 3.0 μbar
1507 MC hits 10 K - start pumping out IVC with turbo. IVC = 2.5 μbar before starting pumpout.
1510 Fill LN2 cold trap bath from bomb Dewar
1522 MC(Cernox)/Sorb/1K Pot = 6.8/5.7/4.60 K
1540 MC(Cernox)/Sorb/1K Pot = 6.68/6.0/4.86 K
1605 MC(Cernox)/Sorb/1K Pot = 6.17/6.4/5.18 K
1705 MC(Cernox)/Sorb/1K Pot = 5.33/6.8/5.44 K

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