| Status | Run 74 in progress. Warmed up to fix IVC leak. Cryostat vacuum jacket pumping overnight. N2 in IVC. |
| 0930 | MC(Cernox) = 277.6 K (40 F). With CVJ pumped out it's rising much more slowly, 0.14 K/hour. Suggests tau_warming of 130 hours, around 5X larger than when there's gas in the CVJ. |
| 1030 | Matt enters lab |
| 1030 | Turbo on CVJ = 19 nbar. With Turbo valved out for 1 minute, CVJ = 190 nbar. |
| 1040 | IVC = 0.55 bar. Start gently pumping out IVC with Scroll Pump |
| 1050 | Start pumping IVC with Turbo Pump |
| 1100 | Remove all small, medium, and large Main Bath bolts |
| 1110 | Remove covers from main bath pit |
| 1120 | Lower Main Bath into pit |
| | oops - the string holding the fastener at the end of one of the cables broke, and I dropped the fastener into the pit. This will be a fun retrieval project… |
| 1130 | OK got the fastener out. Ball of paper towel duct taped to the end of the broomstick, then an inside out layer of duct tape over the end. |
| 1135 | Replace covers on main bath pit |
| 1140 | Pump IVC with Leak Detector and valve out Turbo. Signal settles around 27.0 pbarL/s. |
| 1145 | Squirting helium around the indium seal at the base of the stripline tube causes an increase in signal, but I think it's just drifting up to the stripline elbow. I can get just as much or more increase in signal by squirting way up above the indium. Repeat with indium seal at top of IVC, also no significant signal. So these semi-permanent seals don't seem to have suddenly gone bad. |
| 1150 | Squirt helium around the lower IVC seal, doing 1/8 of the circumference at a time then looking at the LD. Never goes up more than 2 pbarL/s. Guess we can't see the leak when warm. |
| 1155 | Begin slowly filling IVC with N2 |
| 1205 | Erect clean tent, start HEPA fan, clean inside with methanol |
| 1215 | Remove all but two IVC bolts. IVC is now at 1 atm. I'll take a break before opening it. |
| 1250 | Remove IVC bottom |
| 1300 | Examine bottom rim of IVC. Couldn't see any scratches. Polished the surface a bit with Scotch Brite along the entire circumference, taking care to polish in the tangential direction. Noticed grease on the surface of the bottom piece under the indium, likely used more grease than necessary last time. I'll use less this time. |
| 1325 | Put new indium o-ring on bottom of IVC. Less grease - put a little on a wipe, then ran the indium through it, then ran the indium through a dry wipe to remove any excess. |
| 1335 | Attach IVC bottom, inserting several bolts and tightening until the indium is just touching but not compressing it yet. We'll do a quick electrical check to make sure everything is ok. |
| 1345 | Quick electrical check on DIB1/2 (Cable 2/3), all looks good, consistent with 2021 April 13. |
| 1355 | IVC bolts all partially tightened. Start gently pumping out IVC with Scroll Pump |
| 1410 | IVC < 0.1 mbar, switch to pumping with Turbo Pump. Continuing to tighten IVC bolts. |
| 1425 | Turbo on IVC = 0.63 μbar. Bots are pretty tight now. |
| 1430 | Pump on IVC with Leak Detector and valve out Turbo. Signal settle around 21 pbarL/s. A little lower than earlier today, that's promising. |
| 1435 | Squirt helium around bottom IVC seal. No increase in leak signal, good. |
| 1440 | Remove clean tent and store it in pump alley |
| 1445 | Squirt helium near stripline elbow. Leak signal spikes to 200 pbarL/s. |
| 1450 | Put a ring of Q-compound on the bottom side of the fridge insert top plate, around the stripline tube where it goes through the top plate. This probably won't help with the leak, and the Q-compound won't work well when it gets cold, but what the heck, I haven't tried this before. |
| 1455 | Put duct tape around the stripline elbow, except in the front where the bolthole is - can finish it up after raising the main bath. |
| 1505 | Tighten IVC bolts a few more times. |
| 1515 | Put fill funnel back on fridge, then remove covers from pit. |
| 1530 | Raise Main Bath |
| 1530 | Put covers back on pit |
| 1550 | Insert medium (bottom) and large (top) bolts attaching MB to fridge stand. Again, the small bolts which attach the fridge insert to the MB aren't aligned well. I'll try loosening the three brackets again to line up the holes better. |
| 1605 | After loosening everything a little, finally able to get the small bolts started |
| 1625 | OK, finally got everything tightened. |
| 1630 | Finish putting duct tape around stripline elbow |
| 1640 | Turbo on IVC = 100 nbar |
| 1640 | Matt exits lab |