2022/12/05 (Monday)
- Lab in-personnel: Matt
| Status | Run 76 in progress |
|---|---|
| Setup | Cables 2/3/1 → diverter/nothing/nothing → Side2-readout HV CONN 1/3/2 → HV 1(L)/2(R) → DCRC50(3)/DCRC55(1), DCRC33(2)→HV control, NaI trigger signal → DCRCX(4) Lead/poly shield fully assembled. Boron-filled socks covering NaI detectors. PuBe behind lead wall on W side of fridge. NaI array undergoing scan, trigger threshold varies. |
| Warmed up yesterday for thirtieth 5K pumpout. Turbo pumping IVC overnight. | |
| 1056 | Begin LHe transfer @ MB = 6.9% |
| 1100 | MC = 5.68 K |
| 1100 | Turbo on IVC = 0.74 nbar. With Turbo valved out for 1 minute IVC = 7.4 nbar |
| 1105 | Close IVC valves at top of fridge. |
| 1105 | Fill LN2 cold trap bath |
| 1110 | MB = 26.9% |
| 1110 | Turn on 4He pump. Open Recovery valve to 4He pump. Pump out line to 1K pot (speedivalve closed). Check pressure in 1K Pot (with V4a open, 4He pump inlet valve closed). 1K Pot = 0.26 bar on mechanical gauge. |
| 1115 | Pump out 1K Pot slowly, throttling the flow at the valve at the pump inlet, opening just until the pump gets louder, then waiting, then opening a little more, etc. With pump just a little loud, can see pressure go down at the mechanical gauge. When this is low, open valve a bit more. When P2 gets below 30 mbar open valve all the way. |
| 1120 | 4He pump valve open all the way. |
| 1120 | 1K Pot = 3.26 K / 1.9 mbar. G1 (fridge+dump) = 438 mbar, falling. MC = 5.61 K. |
| 1130 | 1K Pot = 3.07 K / 2.0 mbar. G1 (fridge+dump) = 377 mbar. MC = 4.99 K. |
| 1140 | 1K Pot = 3.09 K / 1.9 mbar. G1 (fridge+dump) = 398 mbar. MC = 3.31 K. |
| 1145 | Open 1K Pot needle valve → 15°. 1K Pot → 2.83 K / 5.5 mbar |
| 1146 | End LHe transfer @ MB = 95.7% |
| 1150 | Open 1K Pot needle valve → 30°. 1K Pot → 2.71 K / 7.0 mbar |
| 1200 | Open 1K Pot needle valve → 45°. 1K Pot → 2.46 K / 9.0 mbar |
| 1200 | MC/Still/1KPot = 3.13/3.02/2.42 K. G1(fridge+dump) = 322 mbar. |
| 1400 | MC/Still/1KPot = 1.69/1.72/1.52 K. G1(fridge+dump) = 32 mbar, flattening. |
| 1405 | Close V3 and V9, leaving 36 mbar mixture in dump (G2) |
| 1405 | Turn on 3He pump. G1(condenser) → 42 mbar |
| 1405 | Start circulation through Trap 1. V6 → 12.6%. Condenser peaks at 233 mbar. MC(H35) → 1.37 K. Still → 1.40 K / 24 mbar |
| 1410 | V6 → 13.0%. Condenser(G1) → 330 mbar, keeps rising. MC(H35) → 1.32 K. Still(P1) → 1.36 K / 16 mbar. |
| 1420 | Tape plastic bag over stripline elbow. Use He cylinder regulator to establish as small as possible trickle through hose - put hose in bag. We'll see if extra helium around the stripline elbow makes the helium leakage into the IVC any worse than usual. |
| 1425 | Condenser seems to be slowly peaking around 335 mbar. Maybe not quite peaked but let's continue anyway. |
| 1425 | V6 → 13.4%. Condenser(G1) peaks at 371 mbar. MC(H35) → 1.10 K. Still(P1) → 1.10 K / 2.2 mbar. |
| 1430 | V6 → 13.8%. Condenser(G1) doesn't peak, keeps falling. MC(H35) → 0.98 K. Still(P1) → 1.03 K / 1.2 mbar. |
| 1435 | V6 → 14.4%. Condenser(G1) almost peaks at 278 mbar. MC(H35) → 0.81 K. Still(P1) → 1.00 K / 0.6 mbar. |
| 1445 | V6 → 15.0%. Condenser(G1) almost peaks at 244 mbar. MC(H35) → 0.65 K. Still(P1) → 1.02 K / 0.45 mbar. |
| 1450 | V6 → 100.%. Condenser(G1) peaks at 234 mbar. MC(H35) → 0.42 mK. Still(P1) → 0.99 K / 0.12 mbar. |
| 1510 | MC = 0.10 K |
| 1510 | Open V14 to pull the rest of the mixture out of the dump into circulation. Still peaks at 26 mbar, Condenser peaks at 258 mbar, MC peaks at 102 mK, then all relax again. 1KPot = 1.56 K / 9.3±0.2 mbar. |
| As a diagnostic we'll try setting up the Side1-readout HV board. We'll see whether we get the same problems with leakage at high voltage. | |
| 1515 | Disconnect DCRC1&3, cables from E-box, HV input cable, Vtest probe leads from Side2-readout HV board |
| 1525 | Swap out Side2-readout board from HV case, insert Side1-readout board. (Removed front and left panel, unscrewed 5 posts holding board in case, swapped boards, reassembled.) |
| 1530 | Still = 0.90 mbar. Close V14 |
| 1530 | MC = 40.6 mK |
| 1535 | Connect Side1-readout HV board: Cables 2/3/1 → diverter/nothing/nothing → Side1-readout HV CONN 1/3/2 → HV 1(L)/2(R) → DCRC55(1)/DCRC50(3) note that I've switched the two DCRCs around to match the Run75 Side1-readout setup. I think the reason we had it as 3/1 up to now is that there were noise issues with 1/3 on the Side2-readout board that went away when we swapped. |
| 1550 | Look up phonon settings for Side1 channels from Run75. Then look up phonon settings for Side1 channels from Run76, when we were running 2-sided. Those are more recent, but I needed to work out the channel mapping. We'll use the Run76 settings for lockpoint, squid bias, qet bias. |
| 1605 | Set DCRC1 & 3 phonon settings to what I think are the correct values for Side1 channels. |
| 1605 | MC = 28.8 mK |
| 1610 | Plug in DCRC1&3 and turn on DAQ programs. MC temperature jumps to 60 mK then starts falling. Check phonon channels - only 1 is not railed… |
| 1620 | Tried relocking channels, now there are 2 that are unrailed, still have 4 railed (all DCRC3 channels railed). MC = 41 mK and cooling. |
| 1635 | Tried “manually” zapping SQUIDs using instructions here. I don't think it worked - didn't see any spikes in the still pressure. Actually made some mistakes - first time I forgot to set phonon polarity to 0, second time I forgot to set QET biases to zero. |
| 1635 | MC = 36.8 mK. Cooling slowly. |
| 1640 | On one of the channels that isn't railed (DCRC1pC) tried some QET bias scan, looks like it's stuck in normal. No pulses. |
| 1645 | Turn off DAQ programs and unplug DCRC3. Watch MC - not change in temperature, stuck at 36.3 mK. Unplug DCRC1 - MC temperature rises to 36.6 mK, then falls. Reaches 36.0 mK in a couple of minutes. |
| 1655 | Plug in DCRC3 only. MC temperature continues to cool (35.2 mK and falling). But all channels railed low again. Relocking doesn't help, ADCoffset can't be set low enough to revive them. |
| 1700 | Try “manual” ZAP again, doesn't seem to work. |
| 1710 | Was gonna try SQUID tuning but the SQUID control button on the pulse viewer doesn't do anything. Maybe it's the same problem as the non-working sequencer. |
| 1720 | Power DCRC1 only. MC jumps to 63 mK again. Then cools… Start DAQ programs and look at channels, same as before - pB pC look OK but no pulses, pA is railed low and stuck there. |
| 1725 | We can check HV biasing without looking at phonon channels. As long as the DCRCs are attached (don't need to be powered) the Side1 channels will be grounded. We can apply HV and look at the test resistor. |
| 1730 | Dial HV up to -100.0V nominal, -97.7V actual. We'll wait 5 minutes and see what the leakage does. |
| Vtest relaxed to -18 mV, then jumped to -27 mV, but then started falling again, to -15V and lower. Odd. | |
| 1740 | HV = -97.7 V, Vtest = -12.2 mV, Ileak = -13.4 uA, Vdet = -92.3 V (95%). Not bad. And it's still falling. |
| 1740 | Dial HV up to -150.0V nominal, -147.8V actual. |
| 1741 | HV = -147.8 V, Vtest = -135.4 mV, Ileak = -148.9 uA, Vdet = -88.2 V (60%). And it's flat there. That's bad. |
| 1742 | Dial HV down to -120.0V nominal, -118.0V actual. |
| 1744 | HV = -118 V, Vtest = -66 mV, Ileak = -72.6 uA, Vdet = -88.9 V (75%). Also flat, if not rising slightly. Surprisingly it did not spike up above 0, rather it just tracked the HV with no delay…. |
| 1745 | Dial HV down to -100.0V nominal, -97.7V actual. |
| 1747 | HV = -97.7 V, Vtest = -17.3 mV, Ileak = -19.1 uA, Vdet = -90.1 V (92%). A bit worse than earlier, and the leakage isn't falling. |
| 1750 | Dial HV down to 0V. This causes Vtest to spike well above 0 (to about 160 mV), then relax exponentially. Normal behavior. |
| 1750 | Helium cylinder pressure has dropped from 1220 PSI to 420 PSI since I started dribbling it into the bag at the stripline elbow earlier. Not good! Close the He cylinder valves, stop the flow. |