New Directional and Energy Focusing Time of Flight Mass Spectrometers for Special Tasks in Vacuum and Surface Physics

Abstract

This paper describes a variety of new directionally focusing TOFMS with equal momentum or equal energy acceleration and with no first order dependence on ion velocity in time of flight. This is achieved by combining linear drift spaces with magnetic or electrostatic sector fields. Mathematical expressions for velocity focusing are presented together with the requirements for directional focusing, and the characteristic values of a number of geometries which afford stigmatic imaging are given. With special configurations it is further possible to avoid any first order dependence of resolution on slit width. Finally, the resolution is also strongly influenced by the different means of ion production and acceleration. TOFMS with magnetic sector fields and equal momentum acceleration seem well suited for gas analysis together with the coincidence method, while the combination of a sputteringion source with an electrostatic instrument is particularly promising for the analysis of solids and surfaces.