Star cluster dynamics in a laboratory: electrons in an ultracold plasma

Abstract

Electrons in a spherical ultracold quasineutral plasma at temperature in the\nKelvin range can be created by laser excitation of an ultra-cold laser cooled\natomic cloud. The dynamical behavior of the electrons is similar to the one\ndescribed by conventional models of stars clusters dynamics. The single mass\ncomponent, the spherical symmetry and no stars evolution are here accurate\nassumptions. The analog of binary stars formations in the cluster case is\nthree-body recombination in Rydberg atoms in the plasma case with the same\nHeggie's law: soft binaries get softer and hard binaries get harder. We\ndemonstrate that the evolution of such an ultracold plasma is dominated by\nFokker-Planck kinetics equations formally identical to the ones controlling the\nevolution of a stars cluster. The Virial theorem leads to a link between the\nplasma temperature and the ions and electrons numbers. The Fokker-Planck\nequation is approximate using gaseous and fluid models. We found that the\nelectrons are in a Kramers-Michie-King's type quasi-equilibrium distribution as\nstars in clusters. Knowing the electron distribution and using forced fast\nelectron extraction we are able to determine the plasma temperature knowing the\ntrapping potential depth.\n