2020/02/19 (Wednesday)
| Status | Initial LHe transfer yesterday. Beginning Run 72 cooldown. |
|---|---|
| 0835 | MC(H35)/Sorb/1K Pot = 5.28/8.5/6.72 K. All creeping upward overnight. G1(fridge) = 537.3 mbar (3He pump off). |
| 0840 | Tower = 5.26 K. (Coldplate/Still = 17.4/11.4 K. These clearly don't have good calibrations here.) |
| 0840 | MB = 65.8% / 185 mbar |
| 0845 | Motor A/B = 33.0/24.9 Ω, superconducting. Screw terminal connection 29.4 Ω, also presumably the NbTi is now superconducting. |
| 0850 | Turbo on IVC = 4.0 nbar. With turbo valved out for a minute, IVC = 46 nbar. Open Turbo valve again, we'll keep pumping on IVC. |
| this is a little better than the last successful cooldown. | |
| 0850 | Fill LN2 cold trap bath from bomb Dewar. |
| 0855 | Pump out line leading to 1K Pot with scroll pump |
| 0900 | Switch over to 4He pump. Turn on 4He pump then change pump exhaust to recovery and open valve to recovery lines. |
| 0900 | Check pressure in 1K Pot by closing V4A and opening 1K Pot speedivalve: the mechanical gauge goes up about 0.33 bar. 1K Pot temp falls to 4.0 K. |
| 0910 | Pump out 1K Pot in steps, alternating between V4a and the 1K Pot speedivalve. After 8 iterations get pot down to around 0.13 bar. Then leave V4a open and open 1K Pot speedivalve gradually. Leave 4He pump pumping on pot continuously. |
| 0915 | Tower/MC(H35)/Sorb = 5.23/5.19/4.0 K. MC falling. G1(fridge) = 474.4 mbar, falling. |
| 0915 | 1K Pot = 3.06 K / 3.0 mbar. |
| 0920 | Open 1K Pot needle valve → 10°. 1K Pot → 2.6 K / 10 mbar. MC temperature starts falling much faster. Open 1K Pot needle valve → 20°. 1K Pot → 2.5 K / 16 mbar. MC(H35) = 3.33 K |
| 0925 | Open 1K Pot needle valve → 30°. 1K Pot → 2.5 K / 22 mbar. G1(fridge) = 393.3 mbar Open 1K Pot needle valve → 40°. 1K Pot → 2.5 K / 30 mbar. |
| 0935 | MC(H35) = 2.89 K, Fridge(G1) = 261 mbar. 1K Pot = 2.41 K / 30 mbar. |
| 0940 | 1K Pot pressure suddenly spikes up above 400 mbar, wavers between 200 and 400 mbar. MC(H35) = 2.69 K, Fridge(G1) = 204 mbar |
| 0945 | 1K Pot = 2.31 K / 300±50 mbar. |
| Last time the 1K Pot was colder at this point, below 2 K. But the MC is cooling more slowly too, maybe because of the heavier payload. So that may be a drag on the pot cooling. At least the 1K Pot temperature is falling, albeit slowly. | |
| 1000 | MC(H35) = 2.50 K, Fridge(G1) = 147 mbar. 1K Pot = 2.24 K / 350±30 mbar. |
| 1030 | MC(H35) = 2.47 K, Fridge(G1) = 139 mbar. 1K Pot = 2.20 K / 350±30 mbar. Everything seems to have flattened out, that's a little annoying. |
| we can compare to Run 70 which had the GeHV detector and the aluminum electrode. It was colder by this time. So not sure what the problem is here. | |
| I guess I'll try circulating. Note that currently 3He pump is off and and dump is open to cold LN2 Trap 1 and to fridge. | |
| 1040 | Close V3 and V9, leaving 104 mbar (G2) in the dump. Turn on 3He pump. G1/G2 settle at 145/114 mbar |
| 1040 | Start circulation through Trap 1. V6 → 12.8%. 1K Pot temp/press shoot up, MC temperature falls rapidly to 1.77 K (below lambda point). Condenser peaks at 435 mbar. 1K Pot peaked to 2.7 K / off-scale mbar, then starts to settle again. |
| 1045 | MC(H35) = 1.74 K, G1/G2 = 304/278 mbar and falling, 1K Pot = 2.45 K / 200±30 mbar. |
| 1050 | V6 → 13.0%. No impact on condenser (continues to fall) or 1K Pot |
| 1100 | MC(H35) = 1.78 K (rising), G1/G2 = 184/160 mbar and falling, 1K Pot = 2.28 K / 350±30 mbar. |
| 1105 | V6 → 13.3%. Condenser peaks at 265 mbar. 1K Pot pressure spikes and recovers. MC(H35) falls, → 1.61 K. |
| 1110 | MC(H35) = 1.59 K, G1/G2 = 258/232 mbar and falling, 1K Pot = 2.36 K / 300±30 mbar. |
| 1110 | V6 → 13.5%. Condenser peaks at 280 mbar. Still pressure (P1) now in range, → 200 mbar and falling. 1K Pot pressure spikes and recovers. MC(H35) falls, → 1.50 K. |
| 1115 | MC(H35)/Tower = 1.50/1.51 K, G1/G2 = 277/251 mbar, Still = 130 mbar, 1K Pot = 2.36 K / 260±30 mbar. |
| 1120 | V6 → 13.8%. Condenser peaks at 295 mbar. Still pressure (P1) falls → 24 mbar. 1K Pot rises a little. MC(H35) falls, → 1.39 K. |
| 1125 | MC(H35) = 1.38 K, G1/G2 = 288/260 mbar, Still = 22 mbar, 1K Pot = 2.34 K / 270±30 mbar. |
| 1130 | V6 → 14.2%. Condenser peaks at 310 mbar. Still pressure (P1) falls → 9 mbar. 1K Pot rises a little. MC(H35) falls, → 1.29 K. |
| so cooldown looks ok, but 1K Pot and circulation pressures much higher than usual. I suspect the warmer pot is leading to the higher mixture pressures. Why is the pot running so warm? We can try adjusting the needle valve later. | |
| 1135 | MC(H35) = 1.31 K, G1/G2 = 307/278 mbar, Still = 9 mbar, 1K Pot = 2.35 K / 300±20 mbar. |
| 1140 | V6 → 14.5%. Condenser peaks at 315 mbar. MC wavered around 1.28 K but then quickly fell to 1.15 K (below Al Tc it seems). That caused a second increase in Condenser pressure, from 312→316 mbar. |
| 1145 | MC(H35)/Tower/Coldplate/Still = 1.16/1.17/1.87/1.84 K, G1/G2 = 315/284 mbar, Still = 6 mbar, 1K Pot = 2.36 K / 300±20 mbar. |
| 1150 | Condenser pressure (318 mbar) and MC temperature (1.24 K) are both increasing slowly… |
| 1150 | Try closing 1K Pot needle valve → 30°. Pot T&P fall, → 2.33 K / 55 mbar. Condenser pressure starts falling, MC temperature rise slows down. |
| 1155 | MC(H35) = 1.25 K, G1/G2 = 312/281 mbar, Still = 6 mbar, 1K Pot = 2.32 K / 55 mbar. |
| 1155 | V6 → 14.8%. Condenser peaks at 315 mbar. MC spikes to 1.35 K, then bounces around 1.23 K, then falls below 1.1 K (maybe that was the final struggle to get Al electrode below Tc?). Condenser pressure oscillates a little between 315 and 318 mbar. |
| 1200 | MC(H35) = 0.98 K and falling, G1/G2 = 314/282 mbar, Still = 4.5 mbar, 1K Pot = 2.33 K / 55 mbar. |
| 1210 | MC(H35)/Tower/Coldplate/Still = 0.76/0.78/1.01/1.80 K, G1/G2 = 296/266 mbar and falling, Still = 4.5 mbar, 1K Pot = 2.31 K / 55 mbar. |
| 1215 | V6 → 15.1%. Condenser peaks at 297 mbar. MC falls more quickly, → 0.61 K. Still → 3.8 mbar. |
| 1220 | MC(H35) = 0.55 K, G1/G2 = 292/261 mbar, Still = 3.6 mbar, 1K Pot = 2.30 K / 55 mbar. |
| 1240 | MC(H35)/Tower/Coldplate/Still = 0.50/0.51/0.70/1.76 K, G1/G2 = 278/247 mbar, Still = 3.6 mbar, 1K Pot = 2.28 K / 55 mbar. |
| 1240 | V6 → 100%. Condenser peaks at 298 mbar. MC falls more quickly, → 0.30 K. Still → 0.4 mbar. 1K Pot temp rises a little. |
| 1250 | MC(H35) = 68 mK, G1/G2 = 233/206 mbar and falling, Still = 0.3 mbar, 1K Pot = 2.30 K / 50 mbar. |
| 1310 | MC(H35)/Tower/Coldplate = 34.8/84.2/194 mK, G1/G2 = 163/141 mbar, Still = 1.60 K / 0.24 mbar, 1K Pot = 2.23 K / 55 mbar. |
| 1320 | Tower = 78.0 mK, G1/G2 = 164/142 mbar, Still = 0.24 mbar, 1K Pot = 2.24 K / 55 mbar. |
| 1325 | Open V14 to let the remaining mix out of the dump and into circulation. P1(Still) rises off scale, falls again after a a minute. Condenser peaks at 355 mbar. Tower → 140 mK and rising. 1K Pot temp/press spike to 2.62 K / 250 mbar, pressure falls back to 50 mbar but temperature falls more slowly. |
| 1330 | Tower peaked at 155 mK then started falling again. Condenser pressure and 1K Pot temperature both falling. |
| 1350 | Tower = 77.8 mK, G1/G2 = 147/126 mbar, Still = 0.80 mbar, 1K Pot = 2.21 K / 55 mbar. |
| 1350 | Close V14 |
| 1435 | Screw terminal test. Set up circuit with DC supply, 200 Ω resistor, Fluke multimeter as ammeter, and screw terminal leads in breakout box. Increase power in steps, see if the tower temperature increases. We saw an increase at a few mA and above - generally T rose for a couple minutes then leveled out. |
| V_supply [V] | I_sc [mA] | Tower temp [mK] | wait time [min] |
|---|---|---|---|
| 0 | 0.0 | 74.9 | |
| 0.1 | 0.62 | 74.8 | |
| 0.8 | 3.77 | 75.7 | 2.5 |
| 1.5 | 6.74 | 77.8 | 2.0 |
| 1.5 | 6.77 | 78.9 | 6.0 |
| 2.3 | 10.32 | 83.8 | 2.0 |
| 3.4 | 15.12 | 98.3 | 4.0 |
| Compare with Run 71 test on motor coils. We can definitely apply more DC current to the screw terminal setup without much heating. | |
| 1500 | Work out connections for HV board. Looks like we have DIB 1/3/4 → Stripline 43/41/48 → Cable 3/2/1 → nothing/nothing/accessory_interposer → HV_Conn 1/3/2. This presents a bit of a problem because the accessory interposer board has an extension to the right, but HV Connector 2 is on the left, so the extension interferes with the middle connector. It looks like we can put a “blank” interposer between HV board and accessory interposer, and that will leave room for the other cable connections. |
| 1535 | Plug DCRCs into HV box: HV 1/2 → DCRCX(4)/DCRC55(1) |
| 1540 | Start MIDAS. Set up ODB. Set DCRC1 as master. |
| 1620 | After some fiddling, get MIDAS running and the ODB set up for data from both DCRCs. See some live channels and even a few pulses on DCRC1. |
| 1640 | Set phonon settings on both DCRCs to match an ODB file from Run 70. Check channels - a couple have sorta weak pulses (temperature is high), the rest are railed and far off on their offsets. |
| 1650 | Zap SQUIDS. The tool didn't work with DCRCs set to “1, 4” but I could ZAP them separately. |
| 1700 | Stop MIDAS programs and unplug DCRCs. |
| 1700 | Bent a pin on cable gender changer 3 when I connected cable 3. This probably was causing problems with DCRC4. Swapped with gender changer 4. |
| 1705 | Tower = 73.1 mK, G1/G2 = 145/125 mbar, Still = 0.24 mbar, 1K Pot = 2.21 K / 55 mbar. |
| 1705 | MB = 51.5% |
| 1705 | Fill LN2 cold trap bath from 25L bomb Dewar |
| 1710 | Tower = 72.1 mK. Cooling after disconnecting the DCRCs, was running around 75.5 before the zap, maybe 74 after. |