2022/02/23 (Wednesday)
- Lab in-personnel: Matt, Shubham, Scott
| Status | Run 75 finished. All mixture in dump. LHe Trap and LN2 Trap 1 still have contaminants. Cryostat Vacuum Jacket pumped out. Began deinstallation yesterday, 100mK stage removed. |
|---|---|
| 1340 | Do some electrical checks on the tower while it's still in the fridge. Check continuity of bad Side1pF: 495 Ohm. Check continuity between this and a few other channels: 1-2 kOhm or so. |
| 1400 | Do a more permanent connection between the opposite-side ground planes on the Side2-readout HV board. I had used copper tape and a piece of stranded wire to connect these during the run which improved noise. Now we have thicker wire soldered between them. |
| 1400 | Unplug Tower thermometer to do some measurements of resistance between the individual fridge thermometer wires, testing the hypothesis that these wires aren't well insulated from each other and that that's what's been causing the problems with the Tower thermometer. |
| 1415 | Check for leakage between the fridge thermometer wires by measuring between them at the thermometer breakout board pins. This is the Dsub on the right with the switch set to U02844. Pinout is on a label taped to the box showing V-, I-, V+, I+. All connections between these wires read <0.1 nS, so no shorts seen. As a reality check, plug the thermometer back in and measure between these pins. Between V- and I- and between V+ and I+, see ~ 300 Ohm - this is the lead resistance. Between any other two see ~ 1300 Ohm as expected, because Tower thermometer is 1000 Ohm at RT. |
| 1700 | Finish removing tower: Remove all but 4 screws attaching tower to MC can, and remove spool cap from bottom of tower Attach fridge stand ring to IVC, raise fridge stand to support tower and insert threaded rods Remove remaining tower adapter screws so tower is supported by fridge stand Place scissor jack on red drill case and extend it to support tower stand Begin lowering tower with scissor jack being careful no to snag wires, 600mK rod, striplines Collapse scissor jack to near minimum, tighten threaded rods to support tower, then remove red case and extend jack to support stand Continue lowering tower till jack is at minimum height Remove threaded rods and detach ring from IVC, lower ring to bottom of tower stand rods Pull tower stand on scissor jack out from beneath fridge, pulling rods apart enough to clear IVC Double-bag tower on tower stand and carry stand with tower into cleanroom anteroom. |