We started the venting process for the corner today, including the FCB1 section of the filter cavity attached to BSC3
GVs Closed:
GV2, GV5 (GV7 remains soft closed until repairs are done on the piston cylinder), RV1, FC1, 2, 4, 5.
Dry air dewpoint at vent port = -40.3C
We followed the venting procedure E2300169, until the small burp of dry air into the corner volume, during this "burp" we noticed a small pressure increase at PT114 (CP1 gauge on beamtube side of GV5). There was a clear pressure step from 2.02E-9 to 2.04E-9 Torr at the same time as the dry air burp, see attachment.
We waited for ~15 minutes and repeated the air burp into the corner, again we saw another pressure increase at PT114, though the pressure gauge on the opposite side of CP1 PT124 showed a small decrease at the same time as the pressure increases.
We paused the vent to investigate, PT120, PT114 and PT124 are all pirani/CC gauge pairs and we are investigating if there is any potential crosstalk at the vacuum rack that could be causing this.
More to come.
Corner Vent resumed today, we burped purge air one more time to ~1 torr no pressure step seen on the opposite side of the gate valves.
Continued procedure E2300169, dew point at the purge air point of entry was -44.0C
No further issues encountered, total vent time was ~4 hours, with PT110 up to ~770 torr (PT120 pirani needs atmosphere calibration currently reading ~900 torr).
XBM is currently isolated via GV2 and soft closed GV7, pressure is being maintaned by the XBM turbo station.
Closing WP13153
