2019/05/20 (Monday)
| Status: | Transferred LN2 yesterday |
|---|---|
| 0931 | MC(Cernox) = 4.68 K, Sorb/1K Pot = 8.6/6.8 K, G1 (fridge) = 561 mbar, MB = 38.6% |
| 0938 | Fill LN2 cold trap full. |
| 0940 | IVC = 0.86 nbar, 4.6 nbar with pump valved out. |
| 0956 | Perform 4K electrical check, all good including DIB4 PD SQUID |
| 1015 | We want to look at the shorted channel (ZC-13 PB/DIB3 PB) as we cool down to try and understand the SQUID temperature. Hopefully we can make the SQUID work at these temps. |
| 1020 | Start up MIDAS. Let's set up DCRC3 to look at DIB3. |
| 1045 | Power up DCRC3 and start MIDAS programs. With whatever SQUID settings were left on DCRC3 and QET bias=0, we can see some noise signal on channels PB, PC, PD. PA is railed. |
| 1155 | SQUIDs seem to be working. Adjust DCRC3 PB SQUID settings to SQUID bias/lockpoint = -80/-4 to achieve nice modulation curve. |
| 1202 | Try to tune DCRC3 PD SQUID as well so we can look at SQUID only noise, but it looks stanky. Ah, we ought to Zap SQUIDs. |
| 1203 | Zap DIB 3 SQUIDs |
| 1215 | Tune DIB3 PD SQUID to SQUID bias/lockpoint = -80/-4 to achieve nice modulation curve. |
| 1220 | Just looking at PSDs on the pulse viewer, it looks like DIB3 PD (SQUID only) has very low, flat noise at around 3e-7 (in some units? Not sure how the SQUID tuning GUI PSD is normalized). DIB3 PB has a flat spectrum at 4.2e-6 with R/L roll off as expected for Johnson noise. |
| 1222 | Increase trace length to 52.4288 ms. PSDs look nice. |
| 1227 | MC(Cernox) = 4.75 K, Sorb/1K Pot = 8.7/6.9 K, G1 (fridge) = 557 mbar |
| 1230 | Let's try a baby IbIs with DCRC3 pB. Looks nice and linear with slope of -16.5 mV/uA As described on the Run 70 summary, this implies a wirebond resistance of 5.5 mΩ |
| Ib (uA) | Vo (V) |
|---|---|
| -10 | 0.917 |
| -5 | 0.8349 |
| 0 | 0.7529 |
| 5 | 0.6705 |
| 10 | 0.5868 |
| 1232 | Let's also record some data for further noise analysis. |
|---|---|
| 1234 | Start 100s series with 20 Hz in run randoms and 1000 BOR randoms, DCRC3 PB/PD QET bias = 0 |
| 1235 | Okay, so we'll need to do a LHe transfer soon. After that, we'll start the 1K pot and cool down further. While that's happening, we'll periodically take baby IbIs and randoms data as above to try and track resistances and temperatures at the SQUID card. |
| 1315 | Commence LHe transfer. MB = 34.0% |
| 1400 | Commence LHe transfer. MB = 88.6% |
| 1405 | MC(Cernox) = 4.75 K, Sorb/1K Pot = 6.3/5.0 K, Turbo on IVC = 0.54 nbar, G1 (fridge) = 518 mbar |
| 1406 | Pump out 1K pot line up to speedivalve with scroll pump. |
| 1415 | Switch over to 4he pump. Change pump exhaust to recovery. |
| 1418 | Check pressure in 1K Pot: about 0.17 bar on the mechanical gauge. |
| 1425 | Pump out 1K Pot in steps, alternating between V4a and the 1K Pot speedivalve. After 4 iterations get pot down to < 0.1 bar. Then leave 4He pump pumping on pot continuously. |
| 1427 | 1K Pot = 4.5 K / 0.28 mbar, MC = 4.75 K |
| 1430 | Open 1K Pot needle valve → 10°. 1K Pot → 4.1 K / 0.45 mbar |
| 1435 | Open 1K Pot needle valve → 20°. 1K Pot → 4.1 K / 0.45 mbar Open 1K Pot needle valve → 30°. 1K Pot → 4.1 K / 0.50 mbar Why isn't it cooling? |
| 1440 | Maybe the needle valve is crudded up? Close it and open back to 30°. 1K Pot → 4.1 K / 0.50 mbar |
| 1444 | Open 1K Pot needle valve → 40°. 1K Pot → 4.2 K / 0.55 mbar |
| 1445 | Open 1K Pot needle valve → 50°. No change. Open 1K Pot needle valve → 60°. No change. Open 1K Pot needle valve → 70°. No change. Open 1K Pot needle valve → 80°. No change. |
| 1448 | Close 1K Pot needle valve then open it back up to 90°. 1K Pot → 4.2 K / 0.60 mbar |
| 1454 | Slowly 1K open needle valve until it's 2 full rotation open. No change: 1K Pot → 4.2 K / 0.60 mbar Close 1K Pot needle valve completely. |
| 1459 | This feels like the 1K Pot siphon line is plugged like on 2018\05\16. |
| 1502 | With needle valve closed, close valve at 4He pump and watch P2. It runs off to P2>1000 mbar within a few seconds. |
| 1530 | Played with needle valve a bunch, nothing really seemed to matter. |
| 1545 | With needle valve closed, P2 starts rising to hundreds of mbar. What's going on?? Close 1K Pot speedivalve and P2 starts to fall, but doesn't get below 10s of mbar. Close V4, P2 sits at 10 mbar. |
| 1548 | Try switching pump exhaust from recovery to air. There is a huge whoosh as a bunch of pressure comes out and P2 falls to < 1mbar as it should. Ahhh! We realize that we had opened the 4He pump exhaust to recovery with the yellow valve, but had not opened the red valve connecting the 1K pot exhaust line to recovery! |
| 1556 | Open 1K Pot to recovery with the yellow valve and by opening the red wall valve. |
| 1558 | Do the same 1K pot steps as above: Check pressure in 1K Pot on the mechanical gauge, pump out 1K Pot in steps, alternating between V4a and the 1K Pot speedivalve, until pot is down to < 0.1 bar, then leave 4He pump pumping on pot continuously. |
| 1600 | 1K pot = 4.2 K / 0.50 mbar |
| 1601 | Open 1K Pot needle valve → 10°. 1K Pot → 4.2 K / 0.55 mbar Open 1K Pot needle valve → 20°. 1K Pot → 4.2 K / 0.55 mbar |
| 1605 | Slowly open 1K Pot needle valve. At 60°, P2 rises to 1.7 mbar, but no change in temperature. Open to 80°, no change. |
| 1615 | Again, play with needle valve a bit, opening it as far as 4 full rotations, but P2 never rises above 1.7 mbar and 1K Pot temp never moves far from 4.2 K Now I'm sure the 1K Pot is clogged. We'll have to warm up to 300 K and try again. [image not archived: sad.svg] |
| 1620 | Close 1K Pot needle valve and speedivalve. Close off valve to 4He pump and turn off pump. Close recovery valve |
| 1622 | Stop pumping IVC with turbo. IVC pressure = 3.0 nbar |
| 1627 | Let 2 hose-lengths He into IVC. IVC → 86 ubar. MC and 1K Pot temperatures fall to ~4.3 K |
| 1635 | MB = 87.8%. Recovery rate = 300 sec/cubicft |
| 1640 | Start pumping mix to dump. |
| 1650 | Let 1.9 mbar He gas into vacuum manifold. Then open cryostat vacuum jacket valve to let this into the vacuum jacket. Vacuum jacket → 34 μbar, Recovery rate → 34 sec/cubicft This isn't a very aggressive rate, but it should be fine for overnight. |
| 1710 | Set up webcam connected to jiajin to watch LHe level meter overnight. We'll take a pic every 5 min and sort through them in the morning. It's also updating the website so we can check the level overnight. |
| 1835 | MB = 78.3% |
| 2135 | MB = 70.7% |