An exact solution of the moving boundary problem for the expansion of a plasma cylinder in a magnetic field

An exact analytic solution has been obtained for a uniformly expanding, neutral, infinitely conducting plasma cylinder in an external uniform and constant magnetic field. The electrodynamical aspects related to the emission and transformation of energy have been considered as well. The results obtained can be used in analysing the recent experimental and simulation data.Comment: 5 pages, 1 figur

Cooling force on ions in a magnetized electron plasma

Electron cooling is a well-established method to improve the phase space quality of ion beams in storage rings. In the common rest frame of the ion and the electron beam the ion is subjected to a drag force and it experiences a loss or a gain of energy which eventually reduces the energy spread of the ion beam. A calculation of this process is complicated as the electron velocity distribution is anisotropic and the cooling process takes place in a magnetic field which guides the electrons. In this paper the cooling force is calculated in a model of binary collisions (BC) between ions and magnetized electrons, in which the Coulomb interaction is treated up to second-order as a perturbation to the helical motion of the electrons. The calculations are done with the help of an improved BC theory which is uniformly valid for any strength of the magnetic field and where the second-order two-body forces are treated in the interaction in Fourier space without specifying the interaction potential. The cooling force is explicitly calculated for a regularized and screened potential which is both of finite range and less singular than the Coulomb interaction at the origin. Closed expressions are derived for monochromatic electron beams, which are folded with the velocity distributions of the electrons and ions. The resulting cooling force is evaluated for anisotropic Maxwell velocity distributions of the electrons and ions.Comment: 22 pages, 10 figure

On some generalized stopping power sum rules

The Lindhard-Winther (LW) equipartition sum rule shows that within the linear response theory, the stopping power of an energetic point-charge projectile in a degenerate electron gas medium, receives equal contributions from single-particle and collective excitations in the medium. In this paper we show that the LW sum rule does not necessarily hold for an extended projectile ion and for ion-clusters moving in a fully degenerate electron gas. We have derived a generalized equipartition sum rule and some related sum rules for this type of projectiles. We also present numerical plots for He$^{+}$ ion and He$^{+}$ ion-clusters.Comment: 2 figures, LaTe