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2021/04/06 (Tuesday)

Previous Day

  • Lab in-person: Matt / Zach
  • Virtual partner: Zach / Matt
Status Run 74 in progress. Warmed the fridge to fix short and thermal touch. Helium gas in cryostat vacuum jacket, partially pumped out. Mixture cryocleaned six times. IVC sealed and pumping for several days. Main bath up.
We've been seeing a high leak signal in the IVC, slowly falling as we continue to pump.
1120 Matt enters lab
1120 Turbo on IVC = 16 nbar. With Turbo valved out for 1 minute, IVC = 300 nbar.
1130 Check contents of warm LN2 Trap 2: 3.7 mbar. Pump out with Scroll Pump
1145 Pump on IVC with LD, close Turbo valve and wait 1 minute: 109 pbarL/s.
1150 Let 5.4 mbar He exchange gas into IVC.
1200 Isolate IVC and pump manifold, then connect pumping line to Cryostat Vacuum Jacket pump port and pump out line with Scroll then Turbo pump.
1205 Check pressure in Cryostat Vacuum Jacket: 63 μbar.
Begin pumping out Cryostat Vacuum Jacket with Turbo Pump.
1215 Turbo on Cryostat Vacuum Jacket = 0.74 μbar. With Turbo valved out for 1 minute, Cryostat Vacuum Jacket = 40 μbar.
1220 Check fridge pressures: LHe trap/Condenser/Still = 13.8/0.3/0.81 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
1245 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 42 mbar and starts to rise. Throughput = 6.3 mbar/min.
1250 Check pressure in 1K Pot: 22 mbar on P2. Pump out with Scroll Pump
1255 With 1K Pot speedivalve and needle valve closed, pump on Main bath with scroll pump.
Once P2 < 100 mbar (or 2 mbar this time), open 1K pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 1 mbar on P2.
1305 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.
1310 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.
1315 Pressurize main bath and 1K Pot (both sides) with helium to 365 mbar +1atm on G3, then close 1K Pot speedivalve and needle valve.
1320 Turbo on Cryostat Vacuum Jacket = 0.30 μbar. With Turbo valved out for 1 minute, Cryostat Vacuum Jacket = 19 μbar.
1320 As on 2021 Feb 16, 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%.
1325 P1 falls to 0.095 mbar. That's kinda low, let's adjust V6: close completely then open to 12.4%. Before reopening V6 I opened V3 for a moment to repressurize the still. Adjust V6 up a bit, → 12.7%.
1335 P1 = 0.55 mbar.
1335 Try closing V12a speedivalve. G1 falls as it should, showing we have throughput. Falls at 11.2 mbar/min . Open V12a speedivalve again.
1345 MC(Cernox) = 296.2 K, Sorb = >249 K (max), G2/G1/P1 (circulation) = 685/744/0.75 mbar, Level resistor = 0.982 kΩ
1350 Begin LN2 transfer. LN2 Dewar pressure seems low, we'll try pressurizing it with N2 through the vent like last time.
1355 Start pressurizing LN2 Dewar through the vent with nitrogen. LN2 Dewar gauge → 10.5 PSI.
1355 MC(Cernox) = 296.2 K, Sorb = >249 K (max), G2/G1/P1 (circulation) = 685/744/3.2 mbar, Level resistor = 0.982 kΩ
Let's monitor DIB2 (Cable3) qI Feedback to Chassis, to see if the short reappears.
1405 MC(Cernox) = 295.1 K, Sorb = >249 K (max), G2/G1/P1 (circulation) = 685/744/5.5 mbar, Level resistor = 0.991 kΩ. DIB2 qI FB to Chassis = 0.09 nS.
1415 MC(Cernox) = 289.2 K, Sorb = >249 K (max), G2/G1/P1 (circulation) = 685/743/15.0 mbar, Level resistor = 0.999 kΩ. DIB2 qI FB to Chassis = 0.09 nS.
1415 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 11.8 mbar/min. Open V12a speedivalve again.
1440 MC(Cernox) = 249.9 K, Sorb = >249 K (max), G2/G1/P1 (circulation) = 684/740/offscale mbar, Level resistor = 1.053 kΩ. DIB2 qI FB to Chassis = 0.10 nS.
1440 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 15.5 mbar/min. Open V12a speedivalve again.
1450 Turbo on Cryostat Vacuum Jacket = 0.14 μbar. With Turbo valved out for 1 minute, Cryostat Vacuum Jacket = 4.0 μbar.
1505 MC(Cernox) = 191.2 K, Sorb = >249 K (max), G2/G1/P1 (circulation) = 681/735/offscale mbar, Level resistor = 1.140 kΩ. DIB2 qI FB to Chassis = 0.08 nS.
1515 MC(Cernox) = 170.9 K, Sorb = >249 K (max), G2/G1/P1 (circulation) = 678/733/offscale mbar, Level resistor = 1.194 kΩ. DIB2 qI FB to Chassis = 0.10 nS.
1515 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 27.7 mbar/min. Open V12a speedivalve again.
1520 Matt exits lab
1540 Zach enters lab.
1545 MC(Cernox) = 134.9 K, Sorb = 210 K (max), G2/G1/P1 (circulation) = 668/721/offscale mbar, Level resistor = 1.287 kΩ. DIB2 qI FB to Chassis = 0.07 nS.
1600 MC(Cernox) = 123.3 K, Sorb = 170 K (max), G2/G1/P1 (circulation) = 662/714/offscale mbar, Level resistor = 1.303 kΩ. DIB2 qI FB to Chassis = 26.2 nS.
Looks like the short is back, going to stop the transfer.
1601 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 44.5 mbar/min. Open V12a speedivalve again.
1605 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.
1610 Close V6 and turn off 3He pump.
1615 Zach leaves lab.

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