Ion Microprobe Mass Analyzer

Abstract

This paper describes the development of an instrument which is analogous to an electron microprobe x‐ray analyzer, whereby the electron microprobe is replaced by an ion microprobe, and the x‐ray spectrometer by a mass spectrometer. A duoplasmatron is the primary ion source. The primary ion beam is mass separated to eliminate impurity ions. A probe diameter of less than 2 μ at 2×10⁻¹⁰ A is realized for 12‐kV Ar⁺ ions. A new mass spectrometer was developed with the emphasis on high transmission, yet simple construction. It is stigmatic imaging, double focusing, has a mass‐resolving power of 300 with a solid acceptance angle of 1.5×10⁻² sr (4° half‐angle) and a transmitted‐energy bandwidth of 10%. It consists of an axially symmetrical electrostatic Einzel lens, a 45° spherical condenser sector, and a magnetic field with plane but inclined pole faces, which deflects the beam by 90°. No entrance slit is used. Experimental results are presented.