ABSTRACT
The realm of particle accelerators is effectively that of electromagnetism, where we have also to include aspects of the theory of special relativity since in most cases our particles are moving at some significant fraction of the speed of light. In the earliest accelerators a static DC potential difference was used, but today the predominant method is to utilise time-varying, oscillatory voltages created in resonant cavities; the requirement for particles to pass at the right time to be in phase with this oscillatory voltage is why most accelerators deliver bunched beams of particles. Electromagnetism, meaning the motion and dynamics of charges and currents, is governed in the most general way by Maxwell's equations. The chapter discusses the effect of externally-applied electric and magnetic fields upon charged particles, and also discusses when relativistic effects are important. It examines the exchange of energy between the electromagnetic field and a set of particles, including the exchange of energy with electromagnetic radiation.
