Ion stopping in a magnetized anisotropic electron plasma

Electron cooling is a well-established method to improve the phase space quality of ion in traps and storage rings. A calculation of this process is complicated as the electron velocity distribution is often anisotropic and the cooling process takes place in a magnetic field which guides the electrons. In this paper the drag force and the energy loss are calculated in a model of binary collisions 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. Three kinetical regimes can be identified, depending on the relative magnitude of the distance of closest approach, the cyclotron radius and the pitch of the helical motion. The influence of the magnetic field is ambiguous. The energy loss is reduced if the ion moves parallel to the field, while it is enhanced if the ion velocity has a component transversal to the field. This enhancement is not as large as in the dielectric theory and in previous kinematic models. (C) 2003 Elsevier Science B.V. All rights reserved.