Despite the great progress made during this century in the development and operation of particle accelerators, we are, at the moment, facing severe limitations which impede the attainment of very cold and dense beams of charged particles. These limitations are due to the interparticle Coulomb interactions: intrabeam scattering and space-charge effects.
Recently, there has been interest in the feasibility of producing a crystalline beam. This is a spatially ordered ensemble of circulating particles having very small velocity fluctuations relative to each other. Such a state may be obtainable from an ordinary warm beam through the application of intense and continuous phase-space cooling (e.g. stochastic, electron, laser).
Crystalline beams represent the ultimate in the control of space-charge effects. The study, and eventual attainment, of crystalline beams may lead to a variety of other applications, but will certainly provide a deeper insight into the fundamental limitations of storage rings and particle colliders.