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2021/04/27 (Tuesday)

Previous Day

  • Lab in-person: Matt
  • Virtual partner: Zach
Status Run 74 in progress. Warmed up to fix IVC leak. Cryostat vacuum jacket and IVC pumped out. Haven't cleaned the mixture yet.
1035 Matt enters lab
1040 Check contents of warm LN2 Trap 1: 6.6 mbar. Pump out with Scroll Pump.
1040 Put LN2 Trap 2 in bath and fill bath
1045 Turbo on IVC = 8.6 nbar. With Turbo valved out for 1 minute IVC = 190 nbar.
1050 Start cryocleaning mixture through cold LN2 Trap 2, V6 = 12.6%
1100 Increase V6 → 12.9% to restart flow
1125 Stop cleaning through Trap 2 after 35 min. G2 flow pressure was 590-800 mbar. Pump mixture to dump.
Removed 5.7 mbar.
1055 Check pressure in 1K Pot: 24 mbar on P2, 0.01? atm on mechanical gauge. Pump out with Scroll Pump
1055 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.
1105 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.
1110 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.
1120 Pressurize main bath and 1K Pot (both sides) with helium to 282 mbar +1atm on G3, then close 1K Pot speedivalve and needle valve.
1145 Check fridge pressures: LHe trap/Condenser/Still = 1.8/0.2/0.10 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
1150 Perform mixture throughput test at MC = 300 K using above procedure with 3He pump on. Let G1 rise to 560 mbar before Step 3, then it falls to 42 mbar and starts to rise. Throughput = 6.5 mbar/min.
1155 As on 2021 Apr 15, we will flow mixture through the fridge during LN2 cooldown. Let mixture from dump through cold LN2 Trap 1 to fridge, both sides. Then 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. Open V6 to 12.8%.
1205 P1(Condenser) → 26 mbar. Strange, this is significantly higher than in the past. I started V6 at 12.6% and ticked it up a bit to 12.8%. I'll leave it there.
1210 Try closing V12a speedivalve. G1 falls as it should, showing we have throughput. Falls at 11.0 mbar/min . Open V12a speedivalve again.
1215 Turbo on IVC = 8.6 nbar. With Turbo valved out for 1 minute IVC = 160 nbar.
1220 Let 5.4 mbar He exchange gas into IVC.
1230 Begin LN2 transfer
1230 MC(Cernox) = 293.0 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) = 682/740/off-scale mbar, Level resistor = 0.987 kΩ. DIB2 qI FB to Chassis = 0.11 nS.
1235 LN2 Dewar = 8.0 PSI, pretty low, transfer seems slow. Let's pressurize the Dewar with N2 gas. Adjust regulator on N2 cylinder to 11 PSI.
1240 Opened LN2 Dewar Vent valve enough so that it was making a fairly loud rattling noise. Gauge on Dewar has not increased above 8 PSI, but transfer seems quite fast, significant breeze coming out of the MB exhaust. So close the Vent valve enough so that the noise is mostly gone.
1245 MC(Cernox) = 290.2 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1 (circulation) = 682/738 mbar, Level resistor = 1.052 kΩ. DIB2 qI FB to Chassis = 0.07 nS.
1300 MC(Cernox) = 273.0 K, Sorb = >249 K (max), IVC = 4.0 mbar, G2/G1 (circulation) = 681/736 mbar, Level resistor = 1.099 kΩ. DIB2 qI FB to Chassis = 0.07 nS.
1300 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 14.6 mbar/min. Open V12a speedivalve again.
1315 MC(Cernox) = 237.7 K, Sorb = >249 K (max), IVC = 3.4 mbar, G2/G1 (circulation) = 678/733 mbar, Level resistor = 1.156 kΩ. DIB2 qI FB to Chassis = 0.10 nS.
1315 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 21.7 mbar/min. Open V12a speedivalve again.
1330 MC(Cernox) = 197.5 K, Sorb = >249 K (max), IVC = 2.5 mbar, G2/G1 (circulation) = 675/729 mbar, Level resistor = 1.236 kΩ. DIB2 qI FB to Chassis = 0.07 nS.
1330 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 23.5 mbar/min. Open V12a speedivalve again.
1345 MC(Cernox) = 168.0 K, Sorb = >249 K (max), IVC = 2.2 mbar, G2/G1 (circulation) = 671/725 mbar, Level resistor = 1.282 kΩ. DIB2 qI FB to Chassis = 0.07 nS.
1345 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 30.8 mbar/min. Open V12a speedivalve again.
1400 MC(Cernox) = 148.4 K, Sorb = 206.7 K, IVC = 2.2 mbar, G2/G1 (circulation) = 665/719 mbar, Level resistor = 1.305 kΩ. DIB2 qI FB to Chassis = 0.09 nS.
1400 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 37.7 mbar/min. Open V12a speedivalve again.
1415 MC(Cernox) = 132.7 K, Sorb = 171.7 K, IVC = 1.9 mbar, G2/G1 (circulation) = 659/712 mbar, Level resistor = 1.318 kΩ. DIB2 qI FB to Chassis = 0.07 nS.
1415 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 42.6 mbar/min. Open V12a speedivalve again.
1430 MC(Cernox) = 121.1 K, Sorb = 150.3 K, IVC = 1.9 mbar, G2/G1 (circulation) = 651/704 mbar, Level resistor = 1.326 kΩ. DIB2 qI FB to Chassis = 0.07 nS.
1430 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 45.4 mbar/min. Open V12a speedivalve again.
Getting close to where we were when we stopped last time. This transfer is faster. By the Sorb and the Level Resistor, we're already further along than when we stopped last time. But the MC temperature is not quite as low. We could maybe err a little later since it will be sitting longer till tomorrow morning.
1445 MC(Cernox) = 111.4 K, Sorb = 137.5 K, IVC = 1.9 mbar, G2/G1 (circulation) = 642/694 mbar, Level resistor = 1.329 kΩ. DIB2 qI FB to Chassis = 0.07 nS.
1445 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 44.8 mbar/min. Open V12a speedivalve again.
1455 MC(Cernox) = 106.9 K, Sorb = 133.2 K, IVC = 1.9 mbar, G2/G1 (circulation) = 638/689 mbar, Level resistor = 1.330 kΩ. DIB2 qI FB to Chassis = 0.07 nS.
1455 Stop LN2 transfer. Close both LN2 Dewar valves and N2 gas supply valve on wall. Pull out Level Resistor and put stopper in port. Put ping-pong ball on MB exhaust port.
1500 Close V6 and turn off 3He pump.
1505 Matt exits lab

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