Computer simulation of ion clouds in a Penning trap

Motivated by recent experiments, a series of molecular-dynamics simulations of ions confined in a Penning trap have been performed. The temperature T and the density ${\mathrm{n}}_0$ are such that the correlation parameter Γ is large (Γ=${\mathrm{e}}^2$/akT, where 4π${\mathrm{a}}^3$/3=${\mathrm{n}}_0$). However, because of the relatively small size of the ion cloud, results differ considerably from previous studies of unbounded systems. The ions form concentric spheroidal shells, but diffuse freely on the shells. As Γ increases, diffusion decreases and a distorted 2D hexagonal lattice forms on the outer shells.