Chapter 4 Transporting Charged Particles in Radiofrequency Fields

Abstract

Publisher Summary Transporting charged particles in static electromagnetic fields is efficient at moderate or high particle kinetic energies. At very low energies (units of electron-volts) retaining the stability of motion requires decreasing focusing fields to the level at which parasitic factors, such as contamination of electrode surfaces, contact potentials, parasitic magnetic fields, or just the space charge created by particles, become noticeable and can destroy the particle beam. The alternative to focusing in static fields is charged particle confinement in Radiofrequency (RF) fields that generally possess the property of repelling particles from regions of high field amplitudes into regions of smaller fields. This chapter discusses RF guides operated in vacuum or in a buffer gas at pressures up to several torr. Numerical simulation based on the models of the ion-molecule collisions presented in this chapter presents that at high gas pressures the ion motion in a quadrupole RF field is stable for all ion masses larger than the mass M of the buffer gas molecules.