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2025/03/04 (Tuesday)

Previous Day

* Lab in-personnel: Himangshu, Luke

1156 Check contents of contaminants: ~150 mbar
Pump out fridge lines:
  1. Make sure mixture is isolated in the dump.
  2. Check fridge pressures by opening condenser speedivalve+V1 and still gate valve: LHe trap+Condenser(G1)/Still(P1) = no change/2000+ mTorr(already up, no change).
  3. Connect scroll pump to He-4 pump line, turn it on.
  4. Open pump line valve, V5A, V2A, V4, wait a minute, then open V5.
  5. You're now pumping on the fridge lines. Wait until P1 and G1 flatten out.
  6. Close condenser speedivalve and still gate valve, V1, V5, V2A, V5A and close and turn off the scroll pump.
1320 Pump out 1kpot and main bath:

- Get to baseline on G3 by opening scroll pump valve and V4A. G3 at 0 mbar.

  1. Close scroll pump valve and V4A
  2. Check pressure in 1K Pot on G3 by opening the 1kpot speedivalve. Open V4A and slowly pump out with Scroll Pump by opening the scroll pump valve slowly connected to the 4He line.
  3. Close the 1kpot speedivalve and V4A. close the scroll pump valve.
  4. Open V1A which opens up the line to the main bath (this will cause the line to expand as the gas fills it).
  5. Open V4A and pump on Main Bath with scroll pump, making sure not to overload the scroll pump.
  6. Once P2 < 2 mbar,close V1A and open 1K Pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 10e-1 mbar on P2.
1330 Check pressure in 1K Pot by opening the 1kpot speedivalve. G3 went up, but below the 1st least count mark ~ 20 mbar. Pump out with Scroll Pump
1218 Close 1kpot speedivalve, close scroll pump valve, open V1A which opens up the line to the main bath (this will cause the line to expand as the gas fills it). G3 reads 950 mbar
Main Bath Line has a leak which is causing P3 to be above 40 mbar. This can't explain the fridge issues we have, but certainly needs to be fixed. We will continue LN2 transfer tomorrow after fixing this leak.
1222 Open V4A and pump on Main Bath with scroll pump, making sure not to overload the scroll pump.
1230 P2 < 2 mbar, close V1A. Open 1K Pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 10e-1 mbar on P2.
1252 Once P2< 10e-1 mbar. Close V4A and scroll pump valve.
Flush the 1kpot and main bath:
  1. With the scroll pump pumping on the He-4 pump line, open V5A, V2A, and the vent speedivalve to evacuate the clear hose leading to the He gas line.
  2. Once P2 falls to <10^-1 mbar, close the He-4 pump line valve and turn off the He-4 pump or scroll pump.
  3. Open V1A, V4A, V5A, V2A.
  4. Open the blue valve that connects gas line to IGH - gas is filling the main bath now.
  5. Once the mechanical gauge (connected to the 1kpot speedivalve) reaches 15mmHg, the bath is at ~0.5bar, stop flushing. Close V5A.
  6. Pump out with the scroll pump to < 4 mbar on P2, making sure not to overload the pump.
  7. Close the scroll pump valve and repeat steps 3 to 5 once more
  8. Close the scroll pump and pressurize the main bath and 1K Pot with helium to a few 100 mbar+1atm on G3, then close 1K Pot speedivalve and needle valve.
  9. Close V1A, V4A, V5A, V2A.
1244 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 on P2.
1251 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 on P2.
1258 Pressurize main bath and 1K Pot (both sides) with helium to 1000 mb on G3, then close 1K Pot speedivalve and needle valve, V1a, V4a, V5a, V2a.
We won't flow mixture through the fridge as I would like to do another cryocleaning today
– 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 12.6%.
– Flow mixture through fridge:
  1. Open V9, V13a, V12a+speedivalve, V1, condenser speedivalve, still gate, V3, let things settle.
  2. Turn on 3He pump, after a min, open V6 to 12.6% and close V3.
– P1(Condenser) → 0.05 mbar. (forgot to close V3 right away)
– Turbo on IVC = 12nbar
– Try closing V12a+speedivalve. G1 falls as it should, showing we have throughput. Falls at 10 mbar/min . Open V12a+speedivalve again.
1408 Let 6.3 mbar He exchange gas into IVC, this is a little less than one hose length (connected to the mechanical gauge on the turbo pump)
1410 MC(Cernox) = 296.6 K, Sorb = >249 K (max), IVC = 6.3 mbar, G2/G1/P1 (circulation) = –/–/– mbar, Level resistor = 0.990 kΩ.
1450 Inserted LN2 transfer stick, connected to the LN2 dewar with a hose, inserted the level resistor, disconnected the helium recovery line.

1420 Begin LN2 transfer
1430 MC(Cernox) = 292.7 K, Sorb = >249 K (max), IVC = 5.4 mbar, G2/G1/P1 (circulation) =– mTorr, Level resistor = 1.111 kΩ.
1445 MC(Cernox) = 272 K, Sorb = >249 K (max), IVC = 4.0 mbar, G2/G1/P1 (circulation) =— mTorr, Level resistor = 1.290 kΩ.
1508 MC(Cernox) = 199 K, IVC = 2.5 mbar, G2/G1/P1 (circulation) = — mTorr, Level resistor = 1.354 kΩ.
1531 MC(Cernox) = 158.2 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) =— mTorr, Level resistor = 1.354 kΩ.
1539 MC(Cernox) = 150.0 K, IVC = 2.2 mbar, G2/G1/P1 (circulation) =— mTorr, Level resistor = 1.354 kΩ
Level resister is stable, we know we dont need the full LN2 dewar, end LN2 transfer
1540
1542 Stop LN2 transfer. Close LN2 Dewar valve. Pull out Level Resistor and put stopper in port. Put ping-pong ball on MB exhaust port.
1555 P1 < 100 mTorr. Close V3+speedivalves, V5, V2 then V9 and turn off 3He pump.

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