RGA scans were collected before and after venting the corner station in October. All scans are in SEM mode and attached with notes below.

• Oct. 7:  pre-vent scan represents vertex only with four large ion pumps and three capacitorr NEG pumps valved into main volume of total pressure ~5e-9 Torr. Filament was energized for only 45 minutes.
• Several post-vent scans were collected and attached to this aLOG with total pressure ranging from 5e-8 Torr to 8e-9 Torr:
  • Oct. 23:  post-vent scan of vertex + XBM + YBM with four IPs and three newly regenerated NEGs valved into main volume. Outgassing levels of unwanted HC gases were higher than we had hoped to see. Note that the RGA filament was energized for only 45 minutes to mimic pre-vent conditions. We opened to arms late in the day on Oct. 23.
  • Oct. 24:  post-vent scan of corner & arms (IPs, NEGs, CPs) showing significantly reduced levels of outgassing rates one day after opening BT GVs (see also aLOG 52688)
  • Oct. 29:  post-vent scan of corner & arms (IPs, NEGs, CPs)
  • Oct. 29:  post-vent scan of vertex-only (four IPs, three NEGs) many days after opening BT gate valves. No elevated levels of contaminates when isolating this volume
  • Oct. 29:  post-vent scan of vertex + XBM (i.e. new BSC7 plate). No elevated levels of contaminates when isolating this volume to RGA
  • Oct. 29:  post-vent scan of vertex + XBM + YBM (i.e. new BSC 7/8 plates). No elevated levels of contaminates when isolating this volume to RGA
  • Nov. 27, 2018:  for comparison - post-vent of vertex-only from Nov. 2018 vent (four IPs, three NEGs)

I was concerned about the HC signature shown in Oct. 23 post-vent scan, so today I cycled GV 1,2,5,7 to isolate a potential problem; all scans look satisfactory compared to Oct. 23. The BSC 7,8 doors were cleaned on site, air baked and FTIR sampled. Today we received the pre-bake, post-clean FTIR results from JPL (E1900244) showing some low level residue, but mostly within the LIGO spec of 0.02 microgram/cm^2. The non-vacuum threaded holes used for rigging are extremely contaminated even after Kyle and Chris' best attempt at cleaning them with wand, due to vendor accidentally using silver anti-seize grease. Note that the serial numbers of plates were accidentally stamped on vacuum side. SN001 is on BSC8 and SN002 is on BSC7.

Both plates were sampled with FTIR kit after air baking at 150C for 48 hours; results from JPL were within LIGO specs (<0.02 microgram/cm^2) and received before installing plates (E1900248).

Based on pre and post vent RGA scans from October vent, I conclude that the two scans that look bad are because the filament was not fully warmed up. It should be energized for at least an hour before scanning.