The maximum energy of 3He ions accelerated by current-driven instabilities

Nonlinear development of strong current-driven instabilities can cause selective acceleration of 3He ions through H cyclotron waves with frequencies ω≅2Ω3He (Ω3He is the cyclotron frequency of 3He). Energies of these ions are studied theoretically and numerically. Theoretical expressions for the wave numbers, kparallel and kperpendicular, of the H cyclotron waves with ω≅2Ω3He and for the maximum energy of 3He ions are presented. As initial electron drift speed vd increases, the value of kperpendicular decreases; which leads to the increase in the maximum 3He energy. Simulation results for the wave numbers and for the maximum 3He energy obtained by a two-dimensional, electrostatic, particle code are quantitatively in good agreement with the theory. It is also shown that when the initial electron drift energy is of the order of 10 keV, many 3He ions can be accelerated to energies of the order of MeV/n