2021/06/25 (Friday)
- Lab in-personnel: Matt, Scott, Gabe
| 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) | |
| 1155 | Tower/MC/Coldplate = 83.0/30.1/169 mK, Still = 1.07 K / 0.080 mbar / 0 mW, G1/G2= 199/188 mbar, 1K Pot = 1.64 K / 24±2 mbar. MB= 30.4% |
| Coldplate and Still thermometers are in their “low mode” today, they we in “high mode” yesterday. | |
| We have been moving the source mover. Presumably we are moving toward the far endstop (with + moves). Currently assuming it's working right we have 5.31 mm to go before contacting the far endstop. | |
| Motor driver bias = 8.0 V on the GwINSTEK power supply. | |
| 1155 | Arduino connection is gone so again we'll turn off the driver power output, then reload the Editor page, select COM4, select Monitor, then turn the driver power back on. And then remember to reset Dwell to 40. |
| 1158 | Do mv +128 with dwell = 40. MC rises quickly above 200 mK, then keeps rising. Waveforms start out with V_trimpot = 8V peak-to-peak, stay at that level till near the end of the pulse train - at the end they fall to 6.1 Vpp. Vpower = 10.0 Vpp |
| 1200 | MC peaks at 495 mK. Tower = 2.22 K and falling. |
| Check endstop-to-chassis, still reading <0.2 nS for both near- and far-endstops. | |
| 1230 | Reduce motor driver bias to 7.2 V on the GwINSTEK power supply. |
| 1234 | MC = 36.8 mK and cooling. Tower = 0.27 K and cooling. |
| Double check my spreadsheet keeping track of the moves so far. Looks like I accidentally included an extra +64-step move in the spreadsheet that wasn't actually done. So we are now 4.26 mm away from the far endstop, rather than 3.20 mm. | |
| 1243 | Do mv +128 with dwell = 40. MC rises quickly above 200 mK, then keeps rising. Waveforms start out with V_trimpot = 7.0 Vpp and stay there for the entire pulse train. Vpower = 8.4 Vpp |
| 1245 | MC peaks at 285 mK. Tower = 1.94 K and falling. |
| it certainly looks like 7.2 V is “better” than 8.0 V. Less heating, and for whatever reason it seems like the change we see in coil current over a long pulse train doesn't occur at 7.2 V. | |
| Let's do a +100-step move next. That should move the source 1.65 mm, and bring it to 0.50 mm from the far endstop. | |
| 1307 | MC = 48 mK and cooling. Tower = 0.36 K and cooling. |
| 1310 | Do mv +100 with dwell = 40. MC rises quickly above 150 mK, then keeps rising. Waveforms start out with V_trimpot = 6.9 Vpp and stay there for the entire pulse train. |
| 1311 | MC peaks at 262 mK. Tower = 2.01 K and falling. |
| 1315 | Fill LN2 cold trap bath |
| Check endstop-to-chassis, still reading <0.2 nS for both near- and far-endstops. | |
| 1325 | MC = 85 mK and cooling. Tower = 0.54 K and cooling. |
| 1329 | Do mv +20 with dwell = 40. MC rises quickly above 100 mK, peaks quickly. Waveforms start out with V_trimpot = 6.9 Vpp and stay there for the entire pulse train. |
| 1330 | MC peaks at 118 mK. Tower = 1.18 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.17 mm away from the far endstop. | |
| 1340 | MC = 57 mK and cooling. Tower = 0.43 K and cooling. |
| 1341 | Do mv +4 with dwell = 40. MC rises to 69 mK then falls. V_trimpot = 6.9 Vpp |
| 1342 | MC peaks at 69 mK. Tower = 0.64 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.10 mm away from the far endstop. | |
| 1346 | MC = 52 mK and cooling. Tower = 0.46 K and cooling. |
| 1347 | Do mv +4 with dwell = 40. MC rises to 66 mK then falls. V_trimpot = 6.9 Vpp |
| 1347 | MC peaks at 66 mK. Tower = 0.64 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.04 mm away from the far endstop. | |
| 1351 | MC = 51 mK and cooling. Tower = 0.48 K and cooling. |
| 1353 | Do mv +4 with dwell = 40. MC rises to 66 mK then falls. V_trimpot = 6.9 Vpp |
| 1353 | MC peaks at 64 mK. Tower = 0.62 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.03 mm past the far endstop. | |
| 1357 | MC = 49 mK and cooling. Tower = 0.47 K and cooling. |
| 1402 | Do mv +4 with dwell = 40. MC rises to 62 mK then falls. V_trimpot = 6.9 Vpp |
| 1402 | MC peaks at 62 mK. Tower = 0.64 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.09 mm past the far endstop. | |
| 1405 | MC = 48 mK and cooling. Tower = 0.50 K and cooling. |
| 1407 | Do mv +4 with dwell = 40. MC rises to ?? mK then falls. V_trimpot = 6.9 Vpp |
| 1407 | MC peaks at ?? mK. Tower = 0.67 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.16 mm past the far endstop. | |
| 1411 | MC = 47 mK and cooling. Tower = 0.47 K and cooling. |
| 1412 | Do mv +8 with dwell = 40. MC rises to 81 mK then falls. V_trimpot = 6.9 Vpp |
| 1412 | MC peaks at 81 mK. Tower = 0.87 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.29 mm past the far endstop. | |
| 1417 | MC = 52 mK and cooling. Tower = 0.50 K and cooling. |
| 1418 | Do mv +8 with dwell = 40. MC rises to 83 mK then falls. V_trimpot = 6.9 Vpp |
| 1418 | MC peaks at 83 mK. Tower = 0.88 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.42 mm past the far endstop. | |
| 1423 | MC = 56 mK and cooling. Tower = 0.55 K and cooling. |
| 1424 | Do mv +12 with dwell = 40. MC rises to 95 mK then falls. V_trimpot = 6.9 Vpp |
| 1424 | MC peaks at 95 mK. Tower = 1.05 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.62 mm past the far endstop. | |
| 1446 | Start LHe transfer @ MB = 26.5% |
| 1508 | MC = 31.8 mK. Tower = 0.17 K and cooling. |
| 1514 | Do mv +12 with dwell = 40. MC rises to 87 mK then falls. V_trimpot = 6.9 Vpp |
| 1514 | MC peaks at 87 mK. Tower = 0.96 K and falling. |
| Check endstops-to-chassis, still open. We should now be 0.82 mm past the far endstop. | |
| 1524 | End LHe transfer @ MB = 80.9% |
| 1544 | MC = 32.7 mK and cooling. Tower = 0.18 K and cooling. |
| 1546 | Do mv +12 with dwell = 40. MC rises to 87 mK then falls. V_trimpot = 6.9 Vpp |
| 1546 | MC peaks at 87 mK. Tower = 0.97 K and falling. |
| Check endstops-to-chassis, still open. We should now be 1.02 mm past the far endstop. | |
| 1553 | MC = 50 mK and cooling. Tower = 0.46 K and cooling. |
| 1554 | Do mv +32 with dwell = 40. MC rises above 100 mK and continues to rise. V_trimpot = 6.9 Vpp |
| 1555 | MC peaks at 135 mK. Tower = 1.37 K and falling. |
| Check endstops-to-chassis, still open. We should now be 1.54 mm past the far endstop. | |
| Nick had adjusted the trim pots in series with the coils to get the total resistance close to 120 Ω, to roughly match an unmodified motor at room temperature. Let's check these again and adjust them. | |
| 1605 | Look at purple-gray coil+trim pot: 125.9 Ω. Adjust trim pot to get this to 120.0 Ω Look at black-white coil+trim pot: 129.3 Ω. Adjust trim pot to get this to 120.0 Ω These were pretty close, I don't expect this adjustment to change things much. I also checked the room temperature spare motor, both coils are around 126 Ω. |
| 1613 | MC = 45 mK and cooling. Tower = 0.30 K and cooling. |
| 1614 | Do mv +32 with dwell = 40. MC rises above 100 mK and continues to rise. V_trimpot = 6.8 Vpp. A little surprising that this didn't increase a little with the lowered resistances. |
| 1615 | MC peaks at 139 mK. Tower = 1.34 K and falling. |
| Check endstops-to-chassis, still open. We should now be 2.07 mm past the far endstop. | |
| well this is annoying. We really should be hitting the endstop now. So, still no way to know that it's moving. Or it could be moving inefficiently, skipping steps. Maybe I should try sending the driver signal to only one coil, disconnect the other one. We think that the motor won't move in that case. Then, if most of the heating is due to friction, we should see very little heating. OTOH if most of the heating is due to eddy currents or Joule heating, maybe you'll get about half as much heating. |
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| 1625 | Experiment with the spare motor. Surprisingly, if you disconnect one coil it still moves! It seems to move just as well with only 1 coil as it does with both. |
| 1634 | MC = 45 mK and cooling. Tower = 0.30 K and cooling. |
| 1636 | Do mv +32 with dwell = 40. MC rises above 100 mK and continues to rise. V_trimpot = 6.8 Vpp. |
| 1637 | MC peaks at 138 mK. Tower = 1.46 K and falling. |
| Check endstops-to-chassis, still open. We should now be 2.60 mm past the far endstop. | |
| 1645 | MC = 72 mK and cooling. Tower = 0.53 K and cooling. |
| 1647 | Do mv +32 with dwell = 40. MC rises above 100 mK and continues to rise. V_trimpot = 6.8 Vpp. |
| 1648 | MC peaks at 147 mK. Tower = 1.47 K and falling. |
| Check endstops-to-chassis, still open. We should now be 3.13 mm past the far endstop. | |
| Looking back at 2019 Nov 20 during Run 71 when we jammed the source mover against an endstop. 12 steps after hitting the endstop the temperature increases for each 4-step move after that were lower. We continued to move the source for 11 +4-step moves after it got jammed, like 0.7 mm. | |
| 1724 | MC = 33.4 mK and cooling. Tower = 0.21 K and cooling. |
| 1726 | Do mv +32 with dwell = 40. MC rises above 100 mK and continues to rise. V_trimpot = 6.8 Vpp. |
| 1727 | MC peaks at 134 mK. Tower = 1.49 K and falling. |
| Check endstops-to-chassis, still open. We should now be 3.65 mm past the far endstop. |