2020/09/28 (Monday)
- Lab in-person: Matt
- Virtual partner: Zach, Ruiren
| Setup | Run 73. DIB 1/3/4 → Stripline 43/48/41 → pi-filters 1/2/3 → Cable 3/1/2 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2 → HV 1/2 → DCRCX(4)/DCRC55(1)-master; DCRC33(2) → HV control. DCRCs off. Lead/poly shield erected (4 lead walls, 2 poly walls). |
|---|---|
| Status | Did a partial warming to get helium out of the IVC. Initial LHe transfer 3 days ago… but fridge wouldn't stay cold enough to start 1K Pot. I think the problem turned out to be that I had left the DCRCs on, which seemed to warm the fridge significantly. |
| 0855 | MB = 73.2% |
| 0950 | MC(Cernox)/Sorb/1K Pot = 5.35/8.4/6.56 K. G1(fridge) = 562 mbar (3He pump off). Much better. These values are very close to normal. |
| MC reached a minimum of 5.2 K last night then started arcing up. Sorb and Pot rising too. | |
| 0955 | Matt Fritts body temperature = 96.5 F |
| 1200 | Matt arrives in lab |
| 1205 | Turbo on IVC = 2.5 nbar. With turbo valved out for 1 minutes, IVC = 34 nbar. Open Turbo valve again, we'll keep pumping on IVC. |
| 1205 | Pump out line leading to 1K Pot with scroll pump. Then switch over to 4He pump. Turn on 4He pump then change pump exhaust to recovery and open valve to recovery lines. |
| 1210 | Check pressure in 1K Pot: Mechanical gauge = 0.08 bar. 1K Pot temperature dips to 6.2 K |
| 1215 | Pump out 1K Pot in steps, alternating between V4a and the 1K Pot speedivalve, opening V4a for short bursts only when the mechanical gauge read above a few inches. After 5 iterations leave V4a and 1K Pot speedivalve open. 1K Pot → 4.9 K / 0.5 mbar. Sorb and Fridge pressures fall. MC(Cernox)=5.44 K. |
| 1220 | MC(H35)/Tower = 6.66/8.68 K. (Coldplate/Still = 22.8/10.4 K = 2.487/2.524 kΩ. These don't have good calibrations here.) Tower warmer than usual. |
| 1225 | 1K Pot = 3.83 K / 0.55 mbar |
| 1225 | MC(H35)/Sorb = 6.6/4.8 K. G1 (fridge) = 551 mbar and falling. |
| 1225 | Open 1K Pot needle valve → 10°. 1K Pot → 3.7 K / 0.6 mbar. Practically no change, that's worrying Open 1K Pot needle valve → 20°. 1K Pot → 3.8 K / 0.65 mbar. Crap. |
| 1230 | Open 1K Pot needle valve → 30°. 1K Pot → 3.9 K / 0.75 mbar. Doesn't seem to be working. Grrr. Open 1K Pot needle valve → 60°. 1K Pot → 4.1 K / 0.95 mbar. Not good. Open 1K Pot needle valve → 90°. 1K Pot → 4.2 K / 1.1 mbar. |
| 1235 | Close 4He pump inlet valve, we'll see whether 1K Pot pressure rises. It does rise fairly quickly, off scale on P2, about 1“Hg on the mechanical gauge. Start pumping it again - P2 falls quickly to 1. 1 mbar. 1K Pot temperature doesn't change much, 4.2 K. |
| 1240 | Open 1K Pot needle valve 1 full turn. Finally the pressure reacts a little. 1K Pot → 4.2 K / 4.5 mbar. Temperature not affected… Try opening and closing needle valve a few times. Closed, pressure → 1 mbar; open 1 full turn, pressure → 4-5 mbar. No temperature decrease. |
| 1245 | Open 1K Pot needle valve → 2 full turns. No change in pressure or temperature. |
| Let's do a 1K Pot Throughput Test, like we did on Sep 17, although then we were near room temperature - this is a 4 K test. That one was a He gas throughput test - this I guess is a liquid throughput test. | |
| 1255 | Perform 1K Pot throughput test (at 4 K). Close needle valve then pump out 1K Pot. MB = 69% LHe. Stop pumping and watch the pressure rise at P2. Then repeat, but after stopping pumping open the needle valve a certain amount. This doesn't work the same as the previous room-temperature test: pressure rises off-scale on P2 pretty quickly. Repeating the test with needle valve = 0° versus 30°, it actually looks like a somewhat slower increase in the second case. |
| 1305 | Perform a modified 1K Pot throughput test. With needle valve closed or open to different amounts, close V4a to stop pumping, then time how fast the pressure rises to the 2” mark on the mechanical gauge. (Tap the gauge continuously to unstick the indicator.) Results: Needle valve = 0°/30°/60°/90° → rise time = 37.7/32.3/14.1/10.7 seconds. Interesting but don't really know what it means. 1K Pot temperature remains around 4.0 K. Needle valve = 0°/30°/60°/90° → 108/126/288/380 mbar/min |
| Continue pumping on 1K Pot | |
| 1315 | Tried opening needle valve as much as 5 turns. Pressure never rises above 5 mbar. With needle valve closed, 1 mbar. Tried opening it in steps: rises to 5 mbar at 90°. Then needed to close it all the way for it to fall to 1 mbar again (after some delay). After further messing, found that I could get the pressure to rise at as low as 60° (more in agreement with the throughput test), but there is a delay. |
| OK - 1K Pot is not working. Very lame. Back to square 1. We'll need to warm up. | |
| 1330 | Close 4He pump valve, then switch its outlet to EXHAUST, then turn off 4He pump. |
| 1330 | Open V1a. Since the 1K Pot Speedivalve is open, this lets the He gas from the MB into the Pot, quickly raising its pressure to >1bar. I expected the 1K Pot temperature to change but it barely moves: 1K Pot 4.15→4.23 K. On the other hand, MC(H35) fell very quickly, 6.4→5.2 K. Interesting. |
| 1335 | Open 1K Pot Needle Valve to 5 full turns. |
| We'll leave 1K Pot open to MB through both the Speedivalve and Needle valve, can monitor pressure on G3. | |
| 1335 | G3(MB+1KPot) = 145 mbar. |
| 1350 | Actually before leaving, tried the entire 1K Pot procedure again, to see if letting it up to 1bar made anything different. Pumped it out with Turbo first, then switched to 4He pump. Same behavior. Back to 4He Pump off, 1K Pot open to MB on both sides, V1a open to watch pressure on G3. |
| 1350 | Matt leaves lab. |
todo:
- turn MC/Still Heaters on
- let He into IVC
- let He into CVJ
- if 1K Pot temperature changes, try another throughput test