Late entry from yesterday (7-16): The Kobelco (corner station purge air supply) was switched on at 4 pm. It needs to run at least 12 hrs before vent Today's activities: - The purge air dew point was measured: Right tower (11 am) -42.1 deg C; left tower (11 am) -43.4 deg C; the dew point at the purge port before venting (4:10 pm) -42.2 deg C - Particle counts of the purge air before venting (4 pm; 3 l/min flow rate): 0 pcs. of 5 um or larger particles - The following GVs were closed: GV1, GV2, RV-1, RV-2, FCV-1, FCV-2, FCV-3, FCV-4, and GV5 soft closed (see explanation below) - All the adjacent Ion pumps (IP1, IP2, IP3, IP4, IP14) were valved out - The OMC RGA was valved out, and now is being pumped by an aux cart - The Y-manifold Turbo was switched on and valved in, in order to hold the pressure between GV1 and GV5 - The vent started at 16:15, and lasted until 19:30. This means an overall ~3.9 Torr/min pressure rise, which is a nice slow vent. We hit some ~8 Torr overpressure, and then blew the volume down The reason behind the soft close of GV5: because CP1 is most likely saturated, or at least only has some reduced pumping performance, after closing GV1 and GV2, the pressure of the Y-arm started to rise (notice, that after the close of these 2 GVs, the X-arm CPs were not able to aid the Y-arm CPs). Therefore, the pressure in the Y-manifold started to drop, and the pressure at CP1 (PT-114, PT124) started to raise: this phenomenon would have gone until equilibrium. To avoid the pressure rise of the Y-arm, we soft-closed GV5, and valved in the Y-manifold turbo. This helped, as the pressures are stabilizing now at all areas. This also shows now undeniably, that the pumping performance of CP1 is seriously reduced, and definitely needs regeneration. And, this also explains the relatively high pressures at LHO's corner (notice, that before the vent it was in the low E-8s, while at LLO it is in the mid-low E-9s). Tomorrow, some graphs will be added as a comment in this topic. The pressures: - Corner: atmosphere - Y-manifold: 2.9E-8 Torr - CP1: 4E-9 Torr - CP2: 5.4E-9