2022/03/11 (Friday)
- Lab in-personnel: Matt, Scott, Himangshu, Shubham
| Status | Run 76 prep. Cryostat Vacuum Jacket pumped out. Tower partially installed. Mixture cryocleaned once. |
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| 1105 | Check contents of warm LN2 Trap 1: G1 0.6→20.9 mbar. Pump out with Scroll Pump: G1 20.9→1.4 mbar |
| 1120 | Start cryocleaning mixture through LN2 Cold Trap 2, V6 = 12.4% |
| 1140 | Increase V6 → 12.6% to restart flow |
| 1210 | Increase V6 → 12.7% to speed up flow |
| 1230 | Stop cleaning through Trap 2 after 70 min. G2 flow pressure was 560-670 mbar. Pump mixture to dump. Removed 3.7(2.2) mbar. |
| 1300 | Start cryocleaning mixture through LN2 Cold Trap 1, V6 = 12.8% |
| 1410 | Stop cleaning through Trap 1 after 70 min. G2 flow pressure was 580-760 mbar. Pump mixture to dump. Removed 10.4(9.0) mbar. |
| 1450 | Check contents of warm LN2 Trap 2: G1 2.0→5.7 mbar. Pump out with Scroll Pump: G1 5.7→3.9 mbar |
| 1509 | Start cryocleaning mixture through LN2 Cold Trap 2, V6 = 12.5% |
| 1516 | Increase V6 → 12.6% to restart flow |
| 1547 | Increase V6 → 12.7% to speed up flow |
| 1606 | Stop cleaning through Trap 2 after 70 min. G2 flow pressure was 565-620 mbar. Pump mixture to dump. Removed 4.6(3.2) mbar. |
| 1130 | Plug in source mover controller power. Turn on controller software on laptop. Realize that when the software is turned on that the internal settings are X=0, Y=0, which is not the default physical position. Write a program Set Absolute Position.prg which should be run when the software is turned on. Assuming source is at X=0,Y=96 physically then this program should be run to set the internal coordinates. |
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| 1220 | Testing source mover. Did a few test moves and returned to 0/96. First tries seemed to work. But one trial failed: X=79/Y=34, which according to the spreadsheet calculator should have move the source close to the dib slot and still aligned on the axis pointing to the dib slot. But it didn't seem to do that - and when we reversed the move to get back to 0/96, there was a click and the x-shaft was no longer at its zero. |
| Scott points out that total coil resistance is now twice what it was on the bench (now around 200 Ohm). There are settable delays for how long the motor is powered after a move - these need to be long enough so that the motors have come to rest before you switch off the power. So he suggests trying to adjust the delays. On the bench he had minimized these to the smallest that would work, trying to minimize heating. But maybe they need to be longer now. | |
| 1225 | Reset delays in mover programs from 200 to 500 ms. |
| 1240 | Retry the test with X=79/Y=34. This time the initial move seemed to do the right thing: the collimator moved close to the dib slot. But moving it back to center didn't work: the X shaft does not go back to its zero position. |
| 1410 | More source mover tests. Scott changed settings: HSPD was 100, now 10. LSPD was 10, now 5. (These are “high speed” and “low speed”). Source mover now moves more slowly. Now it seems that the moves have been working correctly. However one should be careful about issuing legal moves. First, a simple mistake would be to enter degree settings into the program instead of microstep settings. We did that once, and the motor banged the side and lost calibration. Second, although the spreadsheet calculator will tell you what is a legal position, one should consider whether intermediate steps are legal. Safest possible thing would be to always move Y back to 96, then move X where you want it, then Y. |
| 1515 | Resume tower installation. Put some copper tape over the DIB slots on the source mover housing, and also at the 30mK base of the tower blocking the gaps at the hex faces. |
| 1525 | Raise tower with scissor jack to full extent, then attach threaded rods to fridge stand and tighten nuts. Collapse jack, put red drill box under stand, then continue to raise tower. |
| 1530 | With tower raised to ~1mm from bottom rim of 30mK can put in three bolts to hold it up, then remove fridge stand. |
| 1540 | Insert and torque all bolts at 30mK can |
| 1600 | Connect thermometer wire and check at LakeShore, looks good. Tape thermometer wire to outside of 30mK can. Screw on spool hole cover plate. |
| 1600 | Check for shorts from detector (phonon channels) to chassis. SHORT! |
| 1700 | Did a lot of troubleshooting looking for the short. We were seeing it when the tower was all the way up but not when it was lowered. Taped a wire to the 30mK can itself to check when the short appeared. We could make it come and go by moving the tower a little. Seemed like it should have been one of the pins at the DIBs hitting to the can but really didn't seem like it, and seems impossible because after then clear the lip at the bottom of the can there's plenty of clearance. Eventually we noticed that the short only appeared when the 60mK rod touched a certain part of the outside of the tower. We had already noticed that certain stages of the tower are electrically isolated from the others. Conclusion: one of the tower wires is shorted to one of the tower temperature stages, specifically one of the phonon wires in use, but not shorted to the 30mK stage. So we missed it during the cleanroom check. |
| 1730 | Remover tower and place in cleanroom anteroom. |
| 1750 | With tower in anteroom did a quick check to see that the 4K stage is electrically isolated from all the others, and that's the one that the detector is shorted to. Checking through each pin found the hard short at (I think) Face 5 pin 7, just 1.2 Ohm. But double checking I caused the short to disappear, then no shorts seen. Was it maybe just the socket touching, and I moved it slightly? Will need to investigate further. |
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