A linear time-of-flight mass spectrometer with relatively high resolution for diagnostic of high energy ion beam

Abstract

A special linear time-of-flight mass spectrometer, with relatively high mass resolution of 120 full width at half maximum (FWHM), for vacuum arc discharge ion source was developed. The instrument comprises a two-electrode ion extraction system, an ion gate, a drift tube, an einzel lens system and a micro channel plate (MCP) detector. Wire type ion gate is used for precise extraction of high energy (up to 40keV) ion beam, and the drift tube length is 1.5m. The extracted ion bunch is focused by the einzel lens system before it arrives the MCP detector, in order to improve the detection efficiency. The low mass ions in plasma extracted during the first few microseconds of discharge process are mainly O+ (m/z 16), C+ (m/z 12), O2+ (m/z 8) and C2+ (m/z 6). The instrument we have described can be a valuable diagnostic tool for high energy ion beam composition. It can be used both in fundamental research and in technological applications such as ion implantation.