We finally got a chance to test a new "high vacuum" style 1600 l/s NEG pump, installed at only EY, on BSC6, at relatively high pressures after the BSC10 vent. At around 3e-5 Torr, I valved in the HV1600 (turned its built-in 10 l/s IP off first), shortly after having spun up the main 2000 l/s turbo pump. After three hours of pumping, I cycled valves in time series below, all while running the RGA in faraday mode. Times are local.

(turbo pump valved in at start)

1. 2:45p:  pressure = 3.4e-6 Torr; valved out NEG
2. 3:00p:  pressure = 3.6e-6 Torr; valved in NEG
3. 3:05p:  pressure = 3.4e-6 Torr; valved out turbo
4. 3:11p:  pressure = 6.9e-6 Torr; valved out NEG (both NEG & turbo valved out here)
5. 3:18p:  pressure = 1.0e-5 Torr; valved in NEG
6. 3:48p:  pressure = 1.2e-5 Torr: valved in turbo

Annotated pressure plots attached.

• PT-410 is cold cathode gauge
• PT-425 is hot cathode wide-range gauge*
• PT-428 is hot cathode wide-range gauge* on NEG housing

*these hot cathode wide-range gauges have a large offset and don't follow pressure readings from cold cathode gauges until it changes emission current at 5.6e-6 Torr

By itself, this NEG pump is not able to maintain the gas load, but does contribute to pumping in high vacuum region.

I haven't had a chance to look at partial pressures yet, but RGA scan is attached.