Charged Particle Optics of Systems with Narrow Gaps: A Perturbation Theory Approach

Abstract

Publisher Summary This chapter presents a wide variety of problems of electron- and ion-optical systems with narrow gaps, based on a perturbation theory approach. A design of any charged particle optical system (electron or ion microscope, energy or mass analyzer, mass separator, particle accelerator, etc.) is always based on simulation of electron or ion trajectories through an electromagnetic field created by a certain set of electrodes, currents, or magnetic pole faces. The analytical calculation of the electromagnetic field disturbance and its influence on charged particle beam distortions in sector field analyzers and Wien filters is presented in the chapter. The method employed in the chapter is based on the idea of the substitution of the Taylor expansion for the field potential written on the optic axis to the boundary conditions defined at distorted electrode or magnet pole surfaces. The chapter describes an extension of the fringing field integral method for sector fields and quadrupole lenses to the case of closely packed arrays of such elements where the fringing fields of the adjacent elements overlap. The chapter also presents an original and elegant analytical method for calculation and synthesis of the electrostatic field distribution with the aid of the multiply divided terminating electrodes in sector analyzers and Wien filters.