Reports until 16:57, Friday 17 February 2012
LHO VE
kyle.ryan@LIGO.ORG - posted 16:57, Friday 17 February 2012 - last comment - 13:35, Wednesday 22 February 2012(2268)
Found main leak on YBM 
Kyle, Gerardo, John  

Found gross leak on dual 3-pin actuator power feed-through on BSC8 (NW) -> Vented YBM, replaced leaker with one that was bench tested and found not to leak.  As found, in-vacuum cables connectors were not screwed to feed-through connectors -> NOTE: flange-to-flange gap is uniform but conflat joint is not "metal-to-metal".  Seems as if flange bolts are bottomed out in blind holes, tapped holes may be too shallow on this one flange(?) -> Pumping YBM overnight with purge/vent valve "cracked" open.
Comments related to this report
gerardo.moreno@LIGO.ORG - 13:35, Wednesday 22 February 2012 (2282)
Link 

Results of inspecting the leaky feedthrough.
It appears that the feedthrough was hit with enough force on the air side to break the weld on the vacuum side.
Photos attached.
Images attached to this comment