Chandra R., Gerardo M., Kyle R.

Today we removed the existing (iLIGO, circa 1998) 2500 l/s ion pump and replaced it with another iLIGO one which had been rebuilt.  GV14 and GV15 were hard-closed throughout the day to facilitate this.

This exercise provided an interesting data point.  The pristinely baked, dry etc... new ion pump internals/interior, though having been vented with dry N2 this morning to prepare it for installation, was, in fact, exposed to the higher-than-normal moist air (raining today) for a few hours while the pump exchanging was taking place.  This exposing is required and purging while being exposed for this short time frame isn't typically needed.  However, today, upon pumping back down, starting the pump and combining it with the X-mid volume, I was surprised at how "wet" the resulting pump had become as a result of this brief room-air exposure.  The resulting pressure was abnormally high and I was hesitant to expose X1 and X2 to this water load.  The interesting part is how rapidly this "water source" was depleted.  What this shows is that the water accumulation on the vacuum baked surfaces while exposed to the wet room air hadn't had enough time to permeate deeply into the surface and was, thus, easily and mostly removed in a short time period upon re-exposure to vacuum - fascinating!