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2020/02/17 (Monday)

Previous Day

Status Tower installed, IVC closed and pumping over weekend.
0900 Turbo on IVC = 34 μbar (? - must be nbar, surely). With Turbo valved out for a few minutes, IVC = 1.2 μbar
0925 Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.4%
0930 Increase V6 → 12.5% to restart flow
0940 Increase V6 → 12.7% to restart flow
0940 Increase V6 → 12.8% to speed up flow
1030 Stop cleaning through Trap 1 after 65 min. G2 flow pressure was 560-680 mbar. Pump mixture to dump.
Removed 4.9 mbar.
1255 Check warm LN2 Cold Trap 1: 4.9 mbar. Pump out Trap 1.
0930 Tighten IVC bottom screws more thoroughly
0940 Start leak checking. LD on IVC: 12 pbarL/s. (With Turbo valved out)
0945 Squirt He generously around lower IVC seal. Leak signal increases a little, to 14 pbarL/s. This may be tolerable.
0945 Squirt He generously around top of stripline tube. Leak signal jumps to 200 pbarL/s. Not great.
1020 Leak is worst when squirting into the joint between the knurled tighteners on the South side. Squirting about 2-meters of He into this area causes the leak signal to rise from 15 to 45 pbarL/s.
1030 Try adjusting the rigid connectors at the top of the fridge to tilt the elbow to the stripline connector slightly to the south. Put a piece of rubber under one of the KF flanges on the north side to push it up a bit. Also try tightening the knurled tighteners by hand - to do so needed to stand on stool on east side crouched under the fridge stand, to get sufficient leverage. These efforts may have improved the leak slightly, now rises to 30 pbarL/s rather than 45 pbarL/s.
1120 Try strapping down rigid tubes on east side to make elbow more level - this seemed to make the leak worse. Noticed leak at KF flange to elbow, tightened it a bit. Got the leak at the stripline tube down to about 30 pbarL/s, probably the best we can do.
1130 Redo electric checks on all DIBS, they look ok, QET B on DIB4 was shorted but shouldn't matter as the thing connected to the QET (motor A) was not shorted.
1315 Check fridge pressures: LHe trap/Condenser/Still = 6.3/0.5/0.7 mbar. Pump out with scroll pump.
Throughput test procedure, Cold Trap 1:
  1. All mixture in dump, LN2 trap 1 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
1335 Perform mixture throughput test at MC = 300 K using above procedure with 3He pump on. Let G1 rise to 550 mbar before Step 3, then it falls to 41 mbar and starts to rise. Throughput = 6.0 mbar/min.
1345 Pump mixture out of fridge and cold LN2 Trap 1 to dump.
1400 Raise the main bath and attach with screws. Everything lined up on the first try.
1410 With 1K Pot speedivalve and needle valve closed, pump on Main bath with scroll pump.
Once P2 < 100 mbar, open 1K pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 1 mbar on P2.
1425 Close off scroll pump, then pressurize bath and 1K Pot (both sides) to about 0.5 bar with helium. Then pump it out again with scroll pump to < 1 mbar.
1430 Close off scroll pump, then pressurize bath and 1K Pot (both sides) to about 0.5 bar with helium. Then pump it out again with scroll pump to < 1 mbar.
1435 Pressurize main bath and 1K Pot (both sides) with helium to 382 mbar +1atm on G3, then close 1K Pot speedivalve and needle valve.
1435 Turbo on IVC = 34 nbar. With turbo valved out for a few minutes, IVC = 860 nbar.
1440 Let 5.4 mbar He exchange gas into IVC
1445 As on 2019 Oct 29, we will flow mixture through the fridge during LN2 cooldown. Let mixture from dump through cold LN2 Trap 1 to fridge, both sides. Then we'll isolate the sides and circulate with V6 open partially and mix open to dump. V9, V13a, V12a+speedi, V1, Condenser speedi, Still gate valves open, 3He pump on. Now open V6 to 12.8%.
1450 P1 falls strangely very low, <1 mbar. Not sure why…
1500 Try closing V12a+speedi. G1 falls as it should, showing we have throughput. Falls at 11 mbar/min. Open V12a+speedi again.
1500 Circulation pressures settling to G2/G1/P1 = 660/721/0.34 mbar
1505 MC(Cernox) = 296.9 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) = 660/721/0.4 mbar, Level resistor = 0.985 kΩ
1515 Begin LN2 transfer
1527 MC(Cernox) = 292.0 K, Sorb = >249 K (max), IVC = 4.6 mbar, G2/G1/P1 (circulation) = 659/721/0.9 mbar, Level resistor = 1.121 kΩ
1527 Close V12a+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 16.5 mbar/min. Open V12a+speedivalve again.
1538 MC(Cernox) = 271.5 K, Sorb = >249 K (max), IVC = 3.0 mbar, G2/G1/P1 (circulation) = 660/720/1.9 mbar, Level resistor = 1.221 kΩ
1550 MC(Cernox) = 237.6 K, Sorb = >249 K (max), IVC = 2.5 mbar, G2/G1/P1 (circulation) = 660/719/3.4 mbar, Level resistor = 1.310 kΩ
1555 Close V12a+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 21 mbar/min. Open V12a+speedivalve again.
1600 MC(Cernox) = 206.1 K, Sorb = >249 K (max), IVC = 2.5 mbar, G2/G1/P1 (circulation) = 660/718/5.0 mbar, Level resistor = 1.34 kΩ
1602 Level resistor reading higher than expected based on previous run, pulled out and placed back in. Closed LN2 dewar valve by <1/4 turn.
1610 MC(Cernox) = 189.5 K, Sorb = 230 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) = 659/718/7.5 mbar, Level resistor = 1.340 kΩ
1615 Close V12a+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 31 mbar/min. Open V12a+speedivalve again.
1620 MC(Cernox) = 173.3 K, Sorb = 190 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) = 659/718/15.0 mbar, Level resistor = 1.340 kΩ
1630 MC(Cernox) = 160.5 K, Sorb = 170 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 659/717/30.0 mbar, Level resistor = 1.339 kΩ
1635 Close V12a+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 42.5 mbar/min. Open V12a+speedivalve again.
1640 MC(Cernox) = 150.1 K, Sorb = 150 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 659/716/45.0 mbar, Level resistor = 1.340 kΩ
1650 Stopped LN2 transfer. Pulled out Level resistor and put ping-pong ball on MB exhaust port.
1650 MC(Cernox) = 141.0 K, Sorb = 140 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 659/716/130.0 mbar, Level resistor = 1.340 kΩ
1700 MC(Cernox) = 134.9 K, Sorb = 130 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 659/716/550.0 mbar
1700 Close V12a+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 52.5 mbar/min. Open V12a+speedivalve again.
1715 MC(Cernox) = 124.7 K, Sorb = 120 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 659/716/(off scale) mbar
1730 MC(Cernox) = 116.8 K, Sorb = 120 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 658/716/(off scale) mbar
1730 Close V12a+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 58 mbar/min. Open V12a+speedivalve again.
1747 MC(Cernox) = 108.8 K, Sorb = 120 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 658/716/(off scale) mbar
1755 Close V12a+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 57.5 mbar/min. Open V12a+speedivalve again.
1800 MC(Cernox) = 104.2 K, Sorb = 120 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 658/716/(off scale) mbar
1804 Filling LN2 cold trap dewar. LN2 dewar ran out part way through filling.
1815 MC(Cernox) = 98.9 K, Sorb = 120 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 658/716/(off scale) mbar
1830 MC(Cernox) = 95.5 K, Sorb = 120 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 658/716/(off scale) mbar
1830 Close V12a+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 58.5 mbar/min. Open V12a+speedivalve again.
1900 MC(Cernox) = 89.1 K, Sorb = 120 K, IVC = 1.6 mbar, G2/G1/P1 (circulation) = 658/715/(off scale) mbar
1900 Close V12a+speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 59 mbar/min. Open V12a+speedivalve again.
1905 Close V6 and stop circulation pump.

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