An introduction to ion optics for the mass spectrograph

A mass spectrograph is an instrument that separates and simultaneously focuses ions, along a focal plane, of different mass/charge ratios that are diverging in direction and that have a variable velocity. With these instruments and a spatially sensitive ion detector, simultaneous detection can be employed, which has been shown to improve precision and throughput (as compared to a mass spectrometer that can only detect one mass at a time). Knowing how an ion beam focuses throughout the mass spectrograph and onto the focal plane is crucial. We present here rudimentary ion optics of the mass spectrograph in a simple yet useable manner. From there, we investigate the direction and energy focal lines of some mass-spectrograph geometries, using the ion optics presented. Lastly, other mass spectrograph geometries that fall outside the field of knowledge of the ion optics covered are discussed. With this review, we hope to provide an understandable and universal ion optic theory that encompasses a wide range of mass spectrographs and that is palatable to the novice as well as the expert. © 1997 John Wiley & Sons, Inc.