2020/03/09 (Monday)
| Setup | Run 72. DIB 1/3/4 → Stripline 43/41/48 → Cable 3/2/1 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1). DCRCs on overnight. Lead/poly shield erected (4 lead walls, 2 poly walls). |
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| Overnight: Tower has been warm since Friday when we disconnected the DCRCs. Yesterday at around noon it was flat at 93 mK and I tried increasing the Still Heater 10→15 mW. It fell to about 90 mK then slowly cooled overnight, but never below 82 mK. | |
| 1020 | Tower/MC/Coldplate = 82.5/73.3/202 mK, Still = 1.65±0.15 K / 0.260 mbar / 15 mW, G1/G2= 637/587 mbar, 1K Pot = 2.27 K / 19 mbar. MB = 29.0% |
| 1030 | Fill LN2 cold trap bath |
| We obviously have a cryo problem. We haven't been able to get below 70 mK since before Friday. I would like to think that the problem is primarily the 1K Pot, and that next time we cool down we can purge it more thoroughly and maybe check the seals and things will work better. But currently the base is getting worse, and yet the 1K Pot behavior doesn't seem to be changing. So maybe something else is wrong - like the leak to the IVC that we saw at the stripline tube, maybe there is buildup of leaked air (or helium) in the IVC that is causing a thermal short. | |
| 1035 | Turbo on IVC = 3.4 nbar. With pump valved out for a few minutes IVC = 46 nbar. this is about the same as the morning after the initial LHe transfer. That was at 4K of course, now it's colder so not sure it's directly comparable. |
| 1130 | Increase Still heat from 15→20 mW. Tower falls 88→85 mK. |
| 1155 | Increase Still heat from 20→30 mW. Tower falls 85→70 mK. Overall: Still Heat 15→30 mW results in G1 610→700 mbar, 1K Pot 2.28→2.36 K / 19→19 mbar, Still 0.24→0.29 mbar. |
| 1445 | Increase Still heat from 30→40 mW. Still Heat 15→30 mW results in G1 =740 mbar, 1K Pot = 2.41 K / 19 mbar, Still =0.32 mbar. Tower temperature rises to 98 mK, then falls a little to 96 mK, then rises again to 100 mK and further… let's try dialing it back. |
| 1520 | Decrease Still heat from 40→30 mW. Tower starts to cool again. |
| Let's try the source mover. | |
| 1540 | Plug in wires from motor filter breadboard to the red motor driver board connected to the Arduino. Purple&Gray / White&Black → A/B on board. This should be the same polarity as Run 71. Plug motor power into CH1 output of GwINSTEK power supply. |
| 1545 | Connect to scope to simultaneously monitor V across the motor coil and V across a trim pot in series with the coil (so essentially V and I of the coil). |
| 1550 | Plug in Arduino power. Red error light, maybe because ethernet is not plugged in; find a live POE port (AN) and cable and plug it in, Arduino board is alive, no red error lights. |
| 1630 | There are some residual networking issues with this device that have not been addressed since the PAN network changes a few weeks ago. Seeking IT assistance with this issue. |
| 1650 | Tower is settling around 82.5 mK. Pulses are weak. MB won't last the night probably, guess we'll proceed to warmup. |
| 1650 | Let's do a one-shot: close V13a, open V9. G2 (dump) falls to 150 mbar. G1 (condenser) falls to 550 mbar and keeps falling. 1K Pot cools, 2.36→2.29 K. Still falls from 0.32→0.26 K. But no immediate decrease in Tower temperature. |
| 1655 | Increase Still heater 30→40 mW. Tower temperature starts rising quickly, above 100 mK. |
| 1700 | Decrease Still power 40→20 mW. Tower continues to rise, 160 mK. Hmm. 1K Pot still falling, now 2.13 K |
| 1705 | Decrease Still power to 0 mW. Tower rises but slows down. 190 mK. G2 (dump) = 202 mbar, maybe most of the 3He is already removed. |
| 1710 | mess around a little more with Still power but this seems futile. Turn off still heater. |
| 1710 | Close 1K Pot needle valve. Falls below 2K, I think that's a first for this run. Pressure → 4 mbar. |
| 1715 | Stop pumping 1K Pot: close 1K Pot Speedivalve, V4a, and valve to 4He pump. Close 1K Pot Recovery valve. Switch 4He pump exhaust valve to Exhaust. Turn off 4He pump. |
| 1720 | Close Turbo pump valve to stop pumping on IVC. We'll see how much it goes up overnight. |
| 1720 | G1 (condenser) = 73 mbar and falling. G2 (dump) = 216 mbar, was rising, now leveling out. Tower = 250 mK, relatively flat. 1K Pot fell to 1.88 K before we stopped pumping on it, now 2.3 K and rising. Still = 0.028 mbar and falling. |
| 1725 | Fill LN2 cold trap bath |
| for now I guess I'll leave it as is: 1K Pot off, pumping mixture out of cold LN2 Trap 1 and fridge to dump. | |
| 1735 | G1 (condenser) = .3 mbar and falling. G2 (dump) = 222 mbar, leveling out. Tower = 305 mK and rising. 1K Pot = 3.0 K and rising. Still = 0.022 mbar. IVC = 46 nbar. |
| 1757 | He recovery meter = 340800 cuft, rate 15 cuft/hour |
| 1800 | Tower = 16.2% |