Vacuum gauge system with a self-compensator for photoelectrons produced in the SPring-8 storage ring

Abstract

Some Bayard–Alpert gauges mounted on crotch chambers in the SPring-8 storage ring have indicated minus pressures or lower pressures due to influx of photoelectrons to their collectors. In order to measure the pressure correctly in such a vacuum environment, the authors proposed a vacuum gauge system 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 can show the real pressure by compensating the ion current measured at the collector of the gauge. The proposed gauge system was developed and tested in an environment of excess electrons using a heater and in an environment of excess ions using an electron gun. In the pressure of the range of 10−7–10−6 Pa, the gauge system showed the real pressure correctly by compensating for charged particles from the external vacuum environments at the SPring-8 storage ring.