Kyle, John 
Plumbed helium into HAM2 annulus pump port via NW40-1/4 swagelok adapter -> Removed O-ring gasket from HAM1 pump port but left NW40 blank in place -> Pressurized annulus volume with helium @ 10 psi (~45 seconds) and confirmed exhaust flow @ HAM1 pump port (NW40 blank "fluttering" as displaced air/helium exited annulus volume -> dialed helium back to < 5 psi for ~90 seconds -> Removed helium connection and purged annulus volume with instrument air 

Note:  Can't ascertain effectiveness of helium getting to "low" portion of septum annulus due to external piping being located at the top of HAM1 and HAM2 septum flanges -> Experience, however, gives me some confidence that a "largish" leak could not go undetected following the above effort. 

Detector baseline reading ~1 x 10-9 torr*L/sec or less during testing -> no response during testing -> no calibration or demonstration of ability to detect helium -> detector behavior typical otherwise