Chapter 1 Charged Particles in Electromagnetic Fields

Abstract

Publisher Summary Electromagnetic fields used in charged particle optics devices are quasistatic. This means that these fields change relatively slowly so that at each time moment they can be considered as static ones. In particular, quasistatic electric and magnetic fields do not influence each other. Although the variety of electrostatic field configurations used in charged particle optical devices is wide, some general types of electrostatic field distributions merit separate mention. A detailed description of the structure and properties of electromagnetic fields can be found in classical monographs. This chapter discusses an important symplectic law relating parameters of motion of single charged particles or their clouds in electromagnetic fields. Two methods are used to create magnetic fields in charged particle optical devices. The first is using permanent magnets. These magnets are formed from very rigid ferromagnetic materials in which the residual magnetization is high enough. Permanent magnets allow manufacturing small magnetic devices. However, the use of permanent magnets is restricted by limited field flux densities produced by such magnets, difficulties of shaping, and by inconvenient lack of the tuning option.