2022/07/26 (Tuesday)
- 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 West side of lead/poly shield. |
| Fridge failure yesterday, looks like an impedance blockage. V6 closed, no circulation. DCRC 1&3 off. | |
| 1110 | MC/Coldplate = 1.77/2.15 K, Still = 1.75 K / pressure offscale / 0 mW, G1/G2 = 264/242 mbar and slowly falling, 1K Pot = 70° / 1.55 K / 8.5±0.5 mbar, MB = 77.4% |
| 1115 | Fill LN2 cold trap bath |
| 1120 | Try pumping mixture to dump to try a throughput test. V13a closed, pumping both sides of fridge through V3 and V5. Still temperature falls to 1.64 K, MC falls a little to 1.68 K. Dump pressure → 65 mbar, rising slowly. |
| Throughput test procedure, Cold Trap 1: |
- All mixture in dump, LN2 trap 1 cold, condenser & still valves open (3He pump on - optional)
- Open V9, V13a, V12a+speedivalve, V3. Wait for G1 to be close to G2.
- Close V12a+speedivalve and V3, open V1
- monitor G1
| 1125 | Perform mixture throughput test at MC = 1.65 K using above procedure with 3He pump on. Let G1 rise to 28 mbar before Step 3, then it falls to 11.7 mbar but doesn't rise. Throughput = 0.8 mbar/min, very low. Although I don't have a very good reference at these low temps - mixture is mostly condensed. |
|---|---|
| 1145 | Pump mixture out of cold LN2 Trap 1 to dump. (Closed off fridge first: V1, Still Gate, Condenser Speedi- valves all closed, so I can pump through V3 and V6. |
| planning to switch to Trap 2. But if I want to pump out Trap 2 I'll need to stop pumping on the 1K Pot, so we can switch the line to the Scroll pump for pumpout. I'll check Trap 2, maybe it's still low. | |
| 1210 | Stop pumping out cold LN2 Trap 1. Check warm LN2 Trap 2: about 10 mbar. Should pump this out. |
| 1210 | Close 1K Pot speedivalve and V4a. Pump out warm LN2 Trap 2 using 4He pump. |
| 1220 | Stop pumping out warm LN2 Trap 2. Start pumping out 1K Pot again, opening 1K Pot speedivalve then opening and closing V4a repeatedly, keeping P2 pressure below about 30 mbar. 1K Pot settles to 1.53 K / 7.0 mbar |
| 1220 | Remove Trap 1 from LN2 trap bath. Put Trap 2 into LN2 trap bath. |
| 1225 | Open Dump to cold LN2 Trap 2 and open V1, V3, Still gate valve, Condenser speedivalve. Fridge open to dump and Trap 2. |
| We'll try circulating, see what happens. | |
| 1415 | Close V3 and V9, leaving 27 mbar (G2) in the dump |
| 1420 | MC = 1.73 K, 1K Pot = 1.56 K / 8.5±0.5 mbar |
| 1420 | Start circulation through Trap 2. V6 → 12.6%. |
| 1430 | Condenser = 333 mbar, hasn't quite peaked yet. MC(H35) → 1.39 K. P1 (still) → 7.5 mbar. |
| 1445 | Condenser = 340 mbar, still rising slowly. MC = 1.34 K and falling. P1 = 5.0 mbar. |
| 1445 | V6 → 13.0%. Condenser(G1) → 408 mbar, rising a little faster. MC(H35) → 1.33 K. Still(P1) → 3.4 mbar. |
| the fact that the condenser pressure never falls doesn't look good. | |
| 1450 | V6 → 13.4%. |
| 1520 | Condenser = 550 mbar, still rising slowly. MC = 1.04 K, oscillating a bit. P1 = 0.40 mbar. |
| 1525 | V6 → 13.8%. |
| 1545 | Condenser = 615 mbar, still rising steadily. MC = 0.96 K and falling. P1 = 0.240 mbar. |
| definitely looks like Still pressure is smaller than normal for this V6 state and MC temperature. | |
| 1545 | V6 → 14.5%. |
| 1600 | Condenser = 655 mbar, still rising steadily. MC = 0.90 K and falling. P1 = 0.440 mbar. |
| 1600 | V6 → 15.0%. |
| gonna have to release the condenser pressure soon, we can just let some into the dump. See how well we can do in one-shot mode, why not. | |
| MC is not as cold as normal by this point, not sure why. That was a symptom of the initial problem too, and not an obvious symptom of a blockage. I don't really know though, likely it's just complicated and not a sign of a separate issue. | |
| 1600 | Still = 0.100 mbar. Turn on Still Heater → 2.0 mW, see what happens. Still pressure → 0.20 mbar. Condenser rises faster, and MC temperature not falling. I think it was doing something like that yesterday too. |
| 1610 | Turn off Still Heater. |
| 1620 | Condenser peaked at 730 mbar but then started falling, interesting. |
| 1630 | Condenser = 702 mbar, no longer falling. Nothing else seems to be changing. MC stuck at 0.90 K, has risen slightly. (Coldplate = 1.08 K) |
| 1635 | V6 → 100%. |
| 1650 | Condenser = 710 mbar rising slowly. MC = 0.87 K, fell a little but pretty flat now. Still → 0.032 mbar, very low. |
| 1650 | Open V9 to release pressure to dump. Condenser falls to 168 mbar. |