{Kyle, Chandra}

This morning we soft closed GV 1,2,5,7 to isolate the vertex, x-beam manifold, and y-beam manifold and connected different calibrated leak checkers to the back end of the main turbo pumps in order to leak check each section separately. We were looking for a big leak based on historical corner pressures (mid -9 Torr range) compared to now (mid -8 Torr range). In short, we found no leaks from spraying helium in a "fire hose" fashion. Note we have leak checked all new joints previously.

First we leak checked the YBM, suspecting IP5 isolation gate valve based IP5's relatively high current. We sprayed all conflats, viewports, purge ports, feedthroughs, large GVs, and some welds and saw no rise in the background of 2.4e-9 mbar-l/s of He.

Then we moved on to the vertex:  started at BSC 1,2,3 and worked our way down to HAM 2 and then down to HAM 5. The He background was quite high:  1.8e-8 Torr-l/s and over the course of 1.5 hrs of spraying large amounts of He gas, the signal gradually rose to 3e-7 Torr-l/s. We did observe a notable rise at the RGA, but after extensive spraying and cycling its isolation valve, conclude there is no major leak at the RGA (above -7 Torr-l/s background, that is). Note that the RGA is close to the leak checker and He could have migrated to its exhaust.

We didn't have time to leak check the XBM, but based on pressure trends (attached), the problem lies within the vertex. We think we're dealing with the aftermath of being up-to-air for three months with nine chamber doors off, in addition to adding spongy materials such as viton, kapton, peek in the main vacuum volume.

AMU 28 is the dominant peak in today's RGA scan.

Corner is being pumped by six large ion pumps (five rebuilt and two with chevron baffles).

The three NEGs were regenerated today and were left valved out for now. Turbos were valved out and spun down at lunch.