2019/04/30 (Tuesday)
| Status | Discovered a blockage Friday. Warm now. Left mixture cooling in LN2 Cold Trap 2 overnight. Removed 5.0 mbar |
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| Setup | DIB1/3/4 → 3.2 MHz filters 2/3/1 → cable 3/1/2 |
| 0820 | Turbo on IVC = 12 nbar. MC(Cernox) = 291.1 K |
| 0820 | DIB4pD SQUID is reading OK, 3.302 kOhm |
| 0820 | |
| 0835 | Can't get 3He pump to start. Keep getting a “HE3 FAIL” light on the power box. Pump motor hums for a 10 seconds or so before the box switches it off. |
| 0920 | Tried removing the motor from the 3He pump. With the motor removed, I can turn it on, and the motor spins. The coupling to the pump can also turn by hand, doesn't seem that hard. But when I reassemble, the motor doesn't seem to be able to turn the pump. I get the hum, then after about 10 seconds the power box shuts it off. Here's a Oerlikon D65B pump manual. |
| I'm also looking at the motor on the “spare” pump. Not sure I know how to wire it. |
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| Wiring on the motor of the 3He pump (the one in use, not the “spare”) |
| 0945 | Disconnected the wiring from the 3He pump and connect to the motor on the “spare” pump after removing the motor. Tried turning it on. Hums, does not spin. |
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| 0955 | Connect the wires back to the motor on the main pump. This one is now also just humming, not spinning. |
| 1020 | With multimeter check voltage on the pins on the outlet from the power supply box, turning 4He and 3He pumps on and off. From the big pin (ground I guess) to the other three, reads 120V ac, except the top pin on the 3He plug is reading about 0 V. |
| 1030 | Investigate inside of power supply box:  The units labeled “He3” and “He4” seem to be switches that I guess close magnetically when the power is on. (Entrelec Schiele KL4S-10.) The red-circled thing seems to be a switch test. The top and bottom leads for the first three wires - red, yellow, blue - read open with an ohmmeter with the switch at 0, and read continuous with the switch at 1 - except for the red one on the He3 unit. So this looks like it needs to be fixed, replaced, whatever. The middle unit is for the unused Roots pump plug, maybe we can swap them? |
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| 1300 | Switch all wires from Switch Bus 2 to Switch Bus 3 and vice versa  Switch Bus 2 had the 3He pump wires and is apparently bad. Now the 3He pump wires are connected to Switch Bus 3, which is hopefully good. The other wires are for the Roots pump, no longer used. Are these the switches that turn these pumps on? I guess so - in which case, we'll have to use the Roots on switch to turn on the 3He pump. Well no, probably not - the last two wires are probably the switch controls, and we swapped them too. Note that the breaker boxes, which seem to be all set to different currents, are still connected to their appropriate pumps. |
| 1310 | Plug in 3He pump and switch it on. It works! |
| 1315 | Pump mixture out of LN2 Cold Trap 2 to dump. |
| 1320 | LN2 Trap 1 is warm. Check contents: 8.2-1.7 = 6.5 mbar on G1. Pump out with scroll pump. |
| 1335 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.7% |
| 1340 | Increase V6 → 13.0% to restart flow |
| 1345 | Increase V6 → 13.1% to speed up flow |
| 1350 | Increase V6 → 13.2% to speed up flow. Too much! G2 rises above 900 mbar. Close V6 again, then open to 13.1%. |
| 1400 | Increase V6 → 13.2% to speed up flow. |
| 1420 | Increase V6 → 13.3% to speed up flow. |
| 1435 | Stop cleaning through Trap 1 after 60 min. G2 flow pressure was 575-910 mbar. Pump mixture to dump. Removed 9.3 mbar |
| 1320 | LN2 Trap 2 is warm. Check contents: 6.4-1.4 = 5.0 mbar on G1. Pump out with scroll pump. |
| 1500 | Check fridge pressures: LHe trap/Condenser/Still = 1.4/0.3/0.14 mbar. Pump out with scroll pump. |
| 1510 | Open dump to both sides of fridge lines via LN2 cold trap 2. |
| 1515 | With 1K Pot speedivalve and needle valve closed, pump on Main bath with scroll pump. Once P2 < 100 mbar, open 1K pot speedivalve and needle valve (5 turns) to pump out 1K pot volume to < 1 mbar on P2. |
| 1515 | Close off scroll pump, then pressurized bath and 1K Pot (both sides) to (SKIP THIS PART: about 0.5 bar with helium. Then pump it out again with scroll pump to < 1 mbar.) Pressurize main bath and 1K Pot (both sides) to 317 mbar +1atm on G3, then close 1K Pot speedivalve and needle valve. |
| 1520 | Turbo on IVC = 10 nbar. With turbo valved out for a few minutes, IVC = 100 nbar. |
| 1525 | Let 5.4 mbar He exchange gas into IVC |
| 1525 | MC(Cernox) = 291.5 K, Sorb = >249 K (max), IVC = 5.4 mbar, G1 (fridge) = 620.5 mbar, Level resistor = 0.987 kΩ. DIB4 pD SQUID = 3.302 kΩ. |
| 1530 | Begin LN2 transfer |
| 1545 | MC(Cernox) = 291.2 K, Sorb = >249 K (max), IVC = 5.4 mbar, G1 (fridge) = 620.9 mbar, Level resistor = 0.992 kΩ. DIB4 pD SQUID = 3.271 kΩ. |
| 1600 | MC(Cernox) = 282.1 K, Sorb = >249 K (max), IVC = 4.6 mbar, G1 (fridge) = 620.7 mbar, Level resistor = 1.002 kΩ. DIB4 pD SQUID = 2.974 kΩ. |
| 1615 | MC(Cernox) = 262.8 K, Sorb = >249 K (max), IVC = 4.0 mbar, G1 (fridge) = 620.7 mbar, Level resistor = 1.010 kΩ. DIB4 pD SQUID = 2.582 kΩ. |
| 1810 | MC(Cernox) = 120.3 K, Sorb = 178.2 K, IVC = 1.9 mbar, G1 (fridge) = 617.0 mbar, Level resistor = 1.279 kΩ. DIB4 pD SQUID = 13 kΩ and dropping (very unstable) Settled to 6.2 kΩ. |
| 1815 | Close valve to LN2 dewar and add closure to pipe on top of fridge, level resistor = 1.26 kΩ. Temperature still falling. |