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2021/06/09 (Tuesday)

Previous Day

  • Lab in-personnel: Matt, Gabe, Scott
Status Run 74 in progress. Warmed up after 3rd appearance of IVC leak at 4K, rebuilt IVC. Cryostat Vacuum Jacket pumped out. Mixture cryocleaned three times.
Passed room temperature leak check, main bath raised
1030 Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.3%
1040 Increase V6 → 12.8% to restart flow
Note: at the end there was no flow. So probably the effective cleaning time was relatively short.
1210 Stop cleaning through Trap 1 after 100 min. G2 flow pressure was 575-755 mbar. Pump mixture to dump.
Removed ?.? mbar.
1210 Turbo on IVC = 34 nbar. With Turbo valved out for 1 minute, IVC = 250 nbar
1230 Check fridge pressures: LHe trap/Condenser/Still = 2.3/0.1/0.08 mbar. Pump out with scroll pump.
Throughput test procedure, Cold Trap 2:
  1. All mixture in dump, LN2 trap 1 cold, condenser & still valves open (3He pump on - optional)
  2. Open V9, V13b, V12b+speedivalve, V3. Wait for G1 to be close to G2.
  3. Close V12b+speedivalve and V3, open V1
  4. monitor G1
1245 Perform mixture throughput test at MC = 300 K using above procedure with 3He pump on. Let G1 rise to 515 mbar before Step 3, then it falls to 37 mbar and starts to rise. Throughput = 5.5 mbar/min.
1250 Check pressure in 1K Pot: 22 mbar on P2, 0.02 atm on mechanical gauge. Pump out with Scroll Pump
1255 With 1K Pot speedivalve and needle valve closed, pump on Main Bath with scroll pump. Once P2 < 2 mbar, open 1K Pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 1 mbar on P2.
1330 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.
1340 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.
1345 Pressurize main bath and 1K Pot (both sides) with helium to 380 mbar+1atm on G3, then close 1K Pot speedivalve and needle valve.
1350 As on 2021 May 4, we will flow mixture through the fridge during LN2 cooldown. Let mixture from dump through cold LN2 Trap 2 to fridge, both sides. Then isolate the sides and circulate with V6 open partially and mix open to dump. V9, V13b, V12b+speedi, V1, Condenser speedi, Still gate valves open, 3He pump on. Open V6 to 12.6%.
1355 P1(Condenser) → 9.0 mbar.
1355 Leak Detector on IVC with Turbo valved out for an hour: 5.7 pbarL/s
1400 Let 6.3 mbar He exchange gas into IVC. (a little higher than the standard 5.4 mbar)
1405 Try closing V12b speedivalve. G1 falls as it should, showing we have throughput. Falls at 10.5 mbar/min. Open V12b speedivalve again.
1405 MC(Cernox) = 296.2 K, Sorb = >249 K (max), IVC = 6.3 mbar, G2/G1/P1 (circulation) = 669/738/110 mbar, Level resistor = 0.995 kΩ.
1425 Begin LN2 transfer
1450 MC(Cernox) = 284.9 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) = 667/734/off scale mbar, Level resistor = 1.014 kΩ.
Looks like transfer is going as fast as last time. We aren't pressurizing the LN2 Dewar, looks like it's got enough pressure on its own. Gauge on Dewar = 10.5 PSI
1515 MC(Cernox) = 244.9 K, Sorb = >249 K (max), IVC = 3.4 mbar, G2/G1/P1 (circulation) = 666/731/off scale mbar, Level resistor = 1.071 kΩ.
1515 Close V12b speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 15.0 mbar/min. Open V12b speedivalve again.
1530 MC(Cernox) = 204.3 K, Sorb = >249 K (max), IVC = 3.0 mbar, G2/G1/P1 (circulation) = 663.5/728.7/off scale mbar, Level resistor = 1.128 kΩ.
1530 Close V12b speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 19.7 mbar/min. Open V12b speedivalve again.
1545 MC(Cernox) = 177.73 K, Sorb = >249 K (max), IVC = 2.5 mbar, G2/G1/P1 (circulation) = 661.4/725.8/off scale mbar, Level resistor = 1.185 kΩ.
1545 Close V12b speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 23.9 mbar/min. Open V12b speedivalve again.
1615 MC(Cernox) = 134.415 K, Sorb = 196.7 K (max), IVC = 2.2 mbar, G2/G1/P1 (circulation) = 651.5/714.2/off scale mbar, Level resistor = 1.291 kΩ.
1615 Close V12b speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 35.9 mbar/min. Open V12b speedivalve again.
1645 MC(Cernox) = 113.169 K, Sorb = 146.6 K (max), IVC = 1.9 mbar, G2/G1/P1 (circulation) = 638.5/699.5/off scale mbar, Level resistor = 1.326 kΩ.
1645 Close V12b speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 43.7 mbar/min. Open V12b speedivalve again.
1655 Stop LN2 transfer. Close LN2 Dewar valve. Pull out Level Resistor and put stopper in port. Put ping-pong ball on MB exhaust port.
1700 Close V6 and turn off 3He pump.

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