gerardo.moreno@LIGO.ORG - posted 17:21, Wednesday 10 January 2018 - last comment - 17:33, Wednesday 10 January 2018(40091)
GV11/12 Hard Closed and CP4 Coupled to Local Ion Pump
(Chandra, Gerardo)
Hard closed GV11 and GV12, this was done in preparation for CP4 bake, at 23:03 utc a small 75 l/s ion pump was coupled to CP4 vacuum volume to remove H2.
Something to note, during the closing of the gate valves, GV11 made a loud noise, visible on some of the local seismometers, also the annulus system for this gate valve responded by going up on current, went from 1 light to 6 lights. GV12 did not make any noise and its annulus system did not show any changes.
To couple the new ion pump to CP4 we followed the steps listed on WP#7270.
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We suspect the sharp step in pressure is from a voltage change in CC gauge when disengaging switches at valve gate pins (for LOTO).