The Crystalline State of Ions

John Schiffer, ANL/PHY

Charged particles under external confinement will form an ordered state if the kinetic energy in their relative motion is small compared to the Coulomb repulsion between them. Such a state has been observed in ion traps and may perhaps be achieved in beams in storage rings. The nature of the ordering is very much influenced by the finiteness of the systems and the boundary conditions. The results of simulations will be discussed in the context of experimental results. Phenomena such as the quasi-crystalline ordering, dimensional phase transitions and normal modes will be discussed, as well as the problems associated with storage rings. Recent work on the role of an effective 'temperature' in a dynamically confined rf-quadrupole ion trap will be shown and results on the coupling between periodic motion and random temperature.