Vacuum gauge self-compensating external environment in the SPring-8 storage ring

Abstract

Some Bayard–Alpert gauges mounted on crotch chambers in the SPring-8 storage ring have indicated negative pressures at stored electron beam currents more than 5 mA. Simple measurements have shown that the negative pressure indications of these vacuum gauges are caused by influx of photoelectrons to their collectors. In order to measure the pressure in such a vacuum environment, the authors propose a vacuum gauge which self-compensates for photoelectrons from the external vacuum environment. The gauge has an added correcting electrode which detects the photoelectron current, only from the external environment, and then compensates to show the real pressure from the measured ion current of the gauge collector.