[Arnab, Chandra, Kyle, Rakesh]

We spent a good part of today setting up for and diagnosing an unidentified known leak (e-7 Torr-L/s range) between GV 5 & 6, where cryopump #1 (CP1) and spool are (corner station, y-arm side). First we checked for inner o-ring leaks by connecting aux turbo cart to GV annuli and pumping and pressurizing (to about 1 Torr) with bottled dry N2 using a control needle valve. Then we soft closed GV6 (with GV5 hard closed) and shortly after valved in the newly installed 55 l/s ion pump (IP) connected to bottom of CP1. Then we walked over to the 10" CETEC GV on CP1 spool to start removing the ISO flange to connect 500 l/s turbo for He leak checking. Kyle checked the CETEC valve to verify it was closed and was able to tighten by a good half turn. We see two pressure bumps that correlate with these activities. We think we fixed the leak by tightening that CETEC valve (and suspect the ISO side is up to air), but won't know for sure until we open GV6 and trend the adjacent gauge (PT-124b), which rises when exposed to CP1 volume (because of leak) and falls when GV6 is closed.

After the pressure at CP1 (PT-114b) started to plateau just above 1e-8 Torr, we valved out the 55 l/s IP for about 10 minutes (without compressing Cu gasket on right angle valve) and valved back in to check response. We are leaving it in this configuration over the weekend - with GV6 soft closed and 55 l/s IP valved in. Dave Barker set a text alert for PT-114b to alarm for pressures above 2e-7 Torr in case the IP turns off.

Note that this volume has been He leak checked in the past by John & Kyle and remained inconclusive after spraying He and seeing no signal on leak checker.