| Status | Run 76 ending |
| Setup | DCRC33(2)→HV control, NaI trigger signal → DCRCX(4) |
| | Warming up. Turbopumping IVC overnight (for more leak checks). Mixture in dump. Warm LN2 Trap 1 clean. NaI array removed and stored in LIGO lab. Lead/poly shield removed. |
| 1147 | Turn on leak detecter to warm up |
| 1156 | Turbo on IVC = 46 nbar. With Turbo valved out for a minute IVC = 1.0 ubar. |
| 1212 | Start leak detector with turbo still pumping, LD on IVC = 17 pbarL/s with IVC = 0.14 ubar. |
| 1213 | Valve out turbo, leak checker settles to LD on IVC = 66 pbarL/s with IVC = 1.6 ubar. |
| 1335 | Use needle to blow small amount of He at stripline elbow joint. Leak increases 66→70, 75-84, etc. - around 5-10 pbarL/s increase. Try raising stripline elbow and putting more vacuum grease in gap between compression rings, pushing up with wood coffee stirrer to try to get to o-ring seal. Does not improve leak. Lower elbow again, push excess grease into gap between rings trying to complete seal. Doesn't improve leak. Blow bigger blast of He at elbow: leak 71→100 pbarL/s, similar increase to yesterday. |
| 1400 | Start removing screws to lower main bath. Loosen medium screws at bottom, two large screws at top, then remove all small screws at top. The shortened 5/16 Allen key that's necessary to remove two screws that are located under fridge insert brackets is kept in the plastic box with the Dewar screws. |
| 1418 | Started lowering the main bath and realized that the hose to the cryostat vacuum jacket is still connected. We go ahead and remove that hose from the main bath and then started lowering it down. |
| | We did some leak checks around the IVC joints, didn't see any leaks. There only seems to be a leak at the stripline elbow. |
| 1530 | Erect clean tent at bottom of fridge around IVC |
| 1530 | Start slowly letting N2 gas into IVC |
| 1545 | IVC is up to 1atm of N2. MC = 283.3 K. |
| | Looked up o-ring sizes, considering whether a tighter o-ring would be better for the stripline elbow. We are using size 222 o-ring. The diagram below shows the cross-section of this and other sizes and how they line up with the OD of the stripline tube, which we measured at 1.507 inches: |
| |  |
| | The 221 size is the same thickness but smaller OD and ID. Looks like it would be much tighter and with a smaller OD it wouldn't be as centered by the ring in the compression clamp. The 324 has a much greater thickness but about the same OD, looks like it would also be even tighter. Probably the best would be something custom - on the bottom is the same OD as the 222 but thicker, 0.15“ rather than 0.139”, therefore a smaller ID. |
| 1720 | Pump out IVC again. We can always refill it tomorrow. I may want to screw around more first with the stripline elbow and leak checks. |