Isolated EX RGA that is bolted to BSC5 empty chamber and observed the main volume pressure immediately decrease. I was monitoring PT-510; starting pressure was 1.97x10^-9 Torr and fell to 1.68x10^-9 Torr several minutes later. Then we mysteriously lost EX vacuum channels and could not read out several pressure gauges including PT-510 (see Gerardo's aLOG 55654). A trend of PT-523 on other side of CP8 is attached, along with the hot cathode wide-range PT-525 gauge on BSC5 (still waiting for PT-510 to recover). 

I connected the leak checker to RGA pump port, removed foil/tape from each conflat joint, one-by-one, while spraying He. The highest signal read from a couple of flanges was 3x10^-9 Torr-L/s of He (background 1x10^-12 Torr-L/s). Next week I'd like to revisit this to pin point the leaky joint(s). We are expecting a much bigger leak in e-7 Torr-L/s range. 

Kyle came by (while honoring social distancing) and cycled the N2 calibration bottle valve in case that was the cause of bigger leak. Next week I will valve RGA back into main volume to measure new pressure. 

RGA is OFF and valved out of main volume. Leak detector is still connected, but valved out of RGA manifold.