Chandra, Gerardo, Kyle 

We would like the option of removing GV12's external gate annulus piping so as to relieve a potential interference with the to-be-installed bake enclosure that will encompass GV12, CP4 and GV11.  This enclosure will allow the bake-out of CP4 as part of its decommissioning.  Removing this external piping requires venting the annulus volume for a long enough duration as to remove the piping, blank-off one of two ports and then install a valve on the unblanked port which would allow the re-evacuation of the vented volume.  Unfortunately, as was the case with GV11, GV12's gate annulus O-rings leak into the adjacent vacuum volumes (Y2 beam tube module and CP4) and thus limit how much time we could tolerate the annulus volume being vented.  We recently demonstrated this by admitting UHP N2 into GV12's gate annulus and then observing the pressure response in the adjacent vacuum volumes.  

Today, in an effort to reduce or eliminate GV12's poor sealing gate, we "slow" opened it by letting the variable speed electric actuation motor ramp up from 0 rpm up to 1000 rpm and then pausing for 30 seconds to allow the "sticky" O-rings to pull away from sealing surface.  This gets repeated a few times until the adjacent volume's pressure gauges confirm that the gate is no longer in contact with the sealing surface.  Once the gate is freed, we then "hard closed" GV12.  Next, we administered ~ 1 LPM of UHP N2 into the entirety (combined) annulus volume for 3 minutes before aborting the gas admission and evacuating.