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2022/03/14 (Monday)

Previous Day

  • Lab in-personnel: Shubham, Himangshu, Matt
Status Run 76 prep. Cryostat Vacuum Jacket pumped out. Mixture cryocleaned five times. Tower installed, IVC turbo pumping for 2 days.
1120 Check contents of warm LN2 Trap 1, then pump out with Scroll Pump: 0.5→6.2→1.8 mbar.
1125 Turbo on IVC = 12 nbar. With Turbo valved out for 1 minute, IVC = 140 nbar.
1130 Start leak detector, connect to IVC. IVC = 19 pbarL/s
1138 Start cryocleaning mixture through LN2 Cold Trap 2, V6 = 12.2%
1143 Increase V6 → 12.4% to restart flow
1222 Increase V6 → 12.6% to speed up flow
1244 Stop cleaning through Trap 2 after 66 min. G2 flow pressure was 570-670 mbar. Pump mixture to dump.
Removed ##(##) mbar.
1215 Complete electrical check on all 3 cables. All looks good except Motor Coil X2 reads open. We will go ahead and proceed with the cooldown but it looks like we won't have a fully functional source mover.
1230 Squirt helium at IVC joints at top of fridge and all indium seals at bottom. No increase in leak signal seen, good.
1318 Raised main bath. Secured with bolts. No issues.
1355 Turbo on IVC = 12 nbar. With Turbo valved out for 1 minute, IVC = 140 nbar.
1405 Check fridge pressures: LHe trap+Condenser/Still = 7.0/1.8 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
1420 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 = 5.9 mbar/min.
1430 Check pressure in 1K Pot: 30 mbar on P2, 0.03 atm on mechanical gauge. Pump out with Scroll Pump
1435 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.
1445 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.
1450 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.
1455 Pressurize main bath and 1K Pot (both sides) with helium to 475 mbar+1atm on G3, then close 1K Pot speedivalve and needle valve.
1515 As on 2021 Nov 30, 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, V13b, V12b+speedi, V1, Condenser speedi, Still gate valves open, 3He pump on. Open V6 to 12.6%.
1520 P1(Condenser) → 0.12 mbar.
1525 Try closing V12a speedivalve. G1 falls as it should, showing we have throughput. Falls at 10.5 mbar/min . Open V12a speedivalve again.
1535 Let 5.4 mbar He exchange gas into IVC.
1550 MC(Cernox) = 298.4 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) = 664/735/0.16 mbar, Level resistor = 0.975 kΩ.
1550 Begin LN2 transfer
1550 Goldman thermometer = 2.043 kOhm.
1600 MC(Cernox) = 296.8 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) = 664/735/0.19 mbar, Level resistor = 1.089 kΩ.
1600 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 24.1 mbar/min. Open V12a speedivalve again.
1630 MC(Cernox) = 227.6 K, Sorb = >249 K (max), IVC = 2.5 mbar, G2/G1/P1 (circulation) = 665/734/0.45 mbar, Level resistor = 1.325 kΩ.
1630 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 23.1 mbar/min. Open V12a speedivalve again.
1700 MC(Cernox) = 165.4 K, Sorb = 195.1 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) = 664/733/1.5 mbar, Level resistor = 1.327 kΩ.
1700 Close V12a speedivalve for 2 minutes to assess throughput. (Condenser pressure G1 should fall.) G1 falls at 41.8 mbar/min. Open V12a speedivalve again.
1723 MC(Cernox) = 135.0 K, Sorb = 145.4 K, IVC = 1.9 mbar, G2/G1/P1 (circulation) = 663.8/732.1/off_scale mbar, Level resistor = 1.327 kΩ.
1730 Stop LN2 transfer. Close LN2 Dewar valve. Pull out Level Resistor and put stopper in port. Put ping-pong ball on MB exhaust port.
1730 Close V6 and turn off 3He pump.

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