Some properties of ion trajectories in the radial plane of an axially symmetric ion trap.

In this article we analyse the trajectories of externally generated ions injected in the radial plane into the ion trap. The shape of the envelope curves for two-dimensional (2D) ion trajectories is determined. Conditions under which these envelope curves can be transformed into circles are found. We show that the amplitude of ion oscillations is a minimum in this case and that this mode corresponds to optimised ion trapping conditions. Also we discuss a ring-shaped ion trap mass spectrometer electrode system which consists of two ring electrodes, and which utilises ion trajectories with circular envelope curves. Copyright 2002 John Wiley & Sons, Ltd.