~1625 - 1630 hrs. local -> Kyle in and out of LVEA Shut down rotating shaft vacuum pumps which had been pumping PT180 (BSC8) for the past 8 days. Also, removed ladder which had been leaning against BSC8. We should now have enough data to compare and contrast PT180's behavior between when it is exposed/pumped by the YBM to that of when exposed/pumped by a locally mounted turbo. Recall that the post-detect era installed Bayard-Alpert gauges PT170, PT180 and PT140 all exhibit a slow upward drift that the iLIGO era Cold Cathode gauges (sampling same vacuum volume) do not. Understanding/believing our gauges is critical. We will decouple the vacuum pumps from PT180 on the next maintenance day.
Pressure reading from PT180 is once again rising after being valved into main volume. We suspect the water load is causing this. End stations show no sign but also get 2.5x more pumping speed from cyropumps due to smaller volume.
PT140 pressure reading on diagonal volume (no crypopump) started dropping this week after a three month incline. These changes are due to LVEA temperature fluctuations.
Correction: water pumping speed is more like 1.8x more at end stations.
Corner volume = 445,000 liters
End volume = 88,000 liters
Corner cyropumping = [100,000 - 3,000] x 2 (L/s)
End cryopuming = 100,000 - 30,000 (L/s)