2021/06/29 (Tuesday)
- Lab in-personnel: Matt
| Status | Run 74 in progress. First cooldown after IVC rebuild. |
|---|---|
| Tower thermometer is reading high, probably this is a thermometer problem and the actual temperature is much lower. High noise in some of the charge channels. | |
| Setup: DIB1/2+acc → SL 41/43 → 3.2 MHz filters → cables 2/3 → nothing/Source_mover_board+HV_diverter_board → DCRC50(3)/55(1). Kepco 40V supplye → HV BNC. No lead/poly shield. (actually currently DCRC55(1) is disconnected. DIB2+acc→SL43→filter→cable3→Source_mover_board) | |
| 1150 | Tower/MC/Coldplate = 85.0/31.5/191 mK, Still = 1.37 K / 0.080 mbar / 0 mW, G1/G2= 207/188 mbar, 1K Pot = 1.63 K / 22±2 mbar. MB = 24.0% |
| 1155 | Fill LN2 cold trap bath |
| Yesterday I convinced myself that the source was at the far endstop, based on lower temperature spikes after the source carriage was stopped by the endstop. I did not see a connection between endstop and ground, suggesting that the endstop wiring is wrong. We started moving the source back toward the center. Plan is to try moving it to the near endstop. We'll try doing -64-step moves with 5 minute wait time between. | |
| Currently the estimated position of the source is y = -32.38 mm, 8.97 mm away from the far endstop. The near endstop is at y = +13.12 mm. | |
| 1159 | Do mvNwait -64steps×41times (stopped after 17, see below), 5 minute wait, with dwell = 40 and power = 7.2 V. First Tower peak @ 3.49 K, minimum 1.49 K |
| This should move the source to y = 10.88 mm, 2.25 mm short of the near endstop. | |
| 1210 | Second move: Tower peak 3.54 K, minimum 1.63 K |
| 1230 | Six moves completed. The temperature spikes are all between 3.48 and 3.56 K. The minima have been increasing: 1.49, 1.63, 1.68, 1.74, 1.82 K. Condenser pressure is climbing. It was 207 mbar this morning, now up to 285 mbar. Still has climbed from 0.080 mbar to 0.150 mbar. |
| 1240 | Nine moves completed. The Tower minimum between moves has crept up to 2.37 K, and the peaks are getting higher too, last one was 3.82 K. Condenser has risen to 301 mbar but seems to be starting to level out. Still = 0.160 mbar. |
| 1320 | 16 moves completed. Last Tower minimum between moves: 2.90 K, last peak: 4.06 K. Condenser has risen to 350 mbar, now rising linearly. Still = 0.180 mbar. |
| Waveforms have changed. They started out about the same as yesterday: V_trimpot = 6.8 V peak-to-peak, Vpower = 8.2 Vpp. Now it's V_trimpot = 5.0 V peak-to-peak, Vpower = 9.2 Vpp. Strange. | |
| 1325 | Stop mvNwait after 17 moves. I hit “disconnect” on the Arduino editor and turned off the driver power output. We'll let it cool down more. |
| 1355 | Cooling slowly. Tower = 1.63 K. Condenser = 327 mbar and falling. Still = 0.130 mbar. |
| 1425 | Cooling slowly. Tower = 1.15 K. Condenser = 288 mbar and falling. Still = 0.110 mbar. |
| 1437 | Start LHe transfer @ MB = 19.5% |
| 1425 | Cooling slowly. Tower = 0.95 K. Condenser = 271 mbar and falling. Still = 0.095 mbar. |
| Let's try a single -64-step move, see if the voltage and current are back to normal. | |
| 1446 | Do mv -64, with dwell = 40 and power = 7.2 V. V_trimpot = 5.1 V peak-to-peak, Vpower = 8.8 Vpp. So this just seems to have changed, not related to temperature Tower peaks @ 3.40 K. Lower than first one during the previous sequence. |
| Suppose we want to target 10mm/hour. Then at 64-step moves you'd want to repeat them every 6min20sec. Or maybe we could try 32-step moves repeated every 3min10sec? | |
| 1453 | At 6min20sec after the move, Tower has cooled to 1.75 K. Is that low enough? It's not quite as cool as after the first move in the mvNwait sequence. |
| 1516 | End LHe transfer @ MB = 91.0% |
| 1548 | Do mvNwait -32steps×6times, 200 second wait, with dwell = 40 and power = 7.2 V. (Around 9.5 mm/hour) First move: V_trimpot = 5.6 V peak-to-peak, Vpower = 8.6 Vpp First Tower peak @ 2.70 K, minimum 1.58 K |
| 1600 | After 5th move: V_trimpot = 4.9 V peak-to-peak, Vpower = 8.8 Vpp, a little different. Tower peak @ 3.15 K, minimum 2.26 K. Condenser has increased from 250→270 mbar, Still 0.080→0.120 mbar. |
| OK let's set up a mvNwait sequence to go for a while after I've left the lab, make it pretty slow. | |
| 1624 | Tower has cooled to 1.45 K. Condenser recently peaked @ 308 mbar, now coming down. |
| 1628 | Do mvNwait -32steps×25times, 10 minute wait, with dwell = 40 and power = 7.2 V. (Around 3.2 mm/hour.) Should finish at 8:38 pm. First move: V_trimpot = 4.9 V peak-to-peak, Vpower = 8.8 Vpp First Tower peak @ 2.75 K, minimum 1.46 K |
| 2135 | This mode was much more stable cryogenically speaking. All 25 Tower temperature peaks were around 2.8 K, with minima around 1.5 K. Condenser pressure rose from around 250 mbar to around 305 mbar and stayed pretty flat during the sequence, then came down again at the end. Still pressure was around 0.135 mbar throughout the sequence. |
| Also of note: at some point the Arduino Editor lost contact with the Arduino, but the sequence continued. I guess the firmware just runs it without needing continued communication with the interface (the update messages are probably sent to the computer from the Arduino, and simply aren't received after the connection is broken). | |
| 2140 | Tower = 0.6 K and cooling |
| 2025 | Tower = 0.2 K and cooling (about 2 hours after the end of the move). This is close to “base” since Tower thermometer flattened out at 186 mK and stayed there overnight. |