2022/08/19 (Friday)
- Lab in-personnel: Giulia, 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 West side of lead/poly shield. |
| 1100 | MC/Coldplate = 28.4/149 mK, Still = 1.12 K / 0.120 mbar / 0 mW, G1/G2 = 150/149 mbar, 1K Pot = 50° / 1.62 K / 19±1 mbar, MB = 39.7% |
| 1112 | Fill LN2 cold trap bath |
| Recent data looks pretty bad. Comparing 0V data from before the recooling to recent, amplitudes seem suppressed and resolution is much worse. I suspect there's a film of helium on the detector. (This may also explain why the QET bias needs to be set higher than before - not because the detector is colder, but because the helium film is increasing the thermal conductance between TES and substrate.) | |
| We'll try warming up enough to boil the helium and pump it out… | |
| 1345 | Close V6 to stop circulation |
| 1350 | Still → 1.25 K / 6 mbar and rising, Condenser (G1) → 100 mbar and falling, MC → 300 mK and rising |
| 1350 | IVC = 19 nbar, no change. |
| 1405 | Still → 1.56 K / 150 mbar and rising, Condenser (G1) → 42 mbar and falling, MC → 530 mK and rising |
| 1405 | Close 1K Pot needle valve |
| 1410 | Sudden jump in MC temperature and huge increase in IVC pressure. MC → 2.1 K, IVC → 2.5 ubar. |
| 1410 | Close 1K Pot speedivalve |
| 1410 | Condenser fell to 40 mbar but now increasing quickly, → 110 mbar. Open V3 to connect Still and Condenser. G1 increases → 240 mbar and rising. |
| 1415 | MC → 3.0 K, IVC → 3.0 ubar. 1K Pot temperature rising, → 2.9 K |
| Notice that during the initial LHe transfer the IVC pressure started to rise during the transfer, climbing to 100 ubar when the MC had cooled to 19 K. (Shubham and Giulia finished the transfer so I missed that this happened.) This is reminiscent of the problems in Run 74, repeated cooldown attempts kept showing rising IVC pressure - this was fixed by complete disassembly and redoing the stripline elbow seal. | |
| 1415 | MC → 3.8 K and flattening, IVC → 3.4 ubar. 1K Pot → 3.9 K and flattening. G1(fridge) → 750 mbar and flattening. Still reads 5.8 K, probably no longer accurate. |
| 1445 | MC = 3.9 K, IVC = 4.0 ubar. 1K Pot = 4.1 K. G1(fridge) = 815 mbar. |
| 1445 | Turn on MC and Still heaters to 20 uW each. G1 and MC start rising a little faster |
| 1505 | MC = 4.4 K, IVC = 4.6 ubar. 1K Pot = 4.3 K. G1(fridge) = 940 mbar. |
| 1505 | Open V9 and V14 to release fridge pressure into dump. This causes a bit of cooling in the MC. Close valves again after a minute. G1 → 544 mbar. |
| 1525 | MC = 4.66 K and flat, IVC = 4.6 ubar. 1K Pot = 4.32 K and flat. G1(fridge) = 600 mbar. |
| ok let's try pumping out the IVC | |
| 1525 | Open Turbo pump valve to start pumping out IVC. Turbo on IVC → 0.12 ubar. No obvious cooling effect, MC and 1K Pot temperatures still flat. |
| 1530 | Turbo on IVC = 74 nbar |
| There may be a slight sign of cooling from pumping: the fridge pressure was increasing steadily before the pumping, now it's plateaued. | |
| 1535 | Turbo on IVC = 30 nbar. With Turbo valve out for 1 minute, IVC = 0.30 ubar. We'll leave the valve closed for a while and see what happens. |
| 1545 | MC(H35) = 4.81 K and flat, IVC = 0.30 ubar. 1K Pot = 4.32 K and flat. G1(fridge) = 605 mbar and pretty flat. |
| so with the Turbo valve closed, the IVC pressure is stable. The fridge pressure is plateaued rather than rising as it was when there was still 4.6 ubar. Not sure exactly what that means… but it does look like we've removed a significant amount of helium. | |
| 1550 | Open Turbo valve to continue pumping out IVC. |
| 1605 | MC(H35) = 5.22 K and rising, Turbo on IVC = 6.3 nbar. 1K Pot = 4.34 K and flat. G1(fridge) = 613 mbar and rising slowly. With Turbo valve out for 1 minute, IVC = 0.12 ubar. Open valve again to continue pumping. |
| 1610 | Begin LHe transfer @ MB = 32.6% |
| Transfer is causing a drop in fridge pressure and somewhat lower 1K Pot temperature, but MC temperature continues to rise. | |
| 1640 | MC(H35) = 6.30 K and rising, Turbo on IVC = 3.0 nbar. 1K Pot = 4.33 K and flat. G1(fridge) = 383 mbar. |
| 1645 | Turn off MC and Still heaters. MC temperature drops. |
| 1658 | End LHe transfer @ MB = 94.7% |
| 1725 | MC(H35) = 5.07 K and falling a little, Turbo on IVC = 1.2 nbar. 1K Pot = 4.24 K and flat. G1(fridge) = 527 mbar. |
| 1800 | MC(H35) = 4.89 K and relaxing, Turbo on IVC = 1.4 nbar. 1K Pot = 4.24 K and flat. G1(fridge) = 551 mbar. With Turbo valve out for 1 minute, IVC = 12 nbar - low!. Open valve again to continue pumping. |