Two-Streaming Cyclotron Instability

A new electrostatic instability of counterstreaming ions occurring at cyclotron frequency is exhibited and discussed. It is conjectured that this instability may provide the mechanism for the enhanced trapping of the injected ion beam in DCX‐II. Stability criteria are developed and in the limit of high anisotropy of the ions and not‐too‐cold electrons, the criterion becomes approximately $\frac{1}{2}{\mathrm{M\hspace{0.17em}}}_i{v}_s^2{\mathrm{<\kappa T}}_e\text{/4}$ (unstable), where M_i is the ion mass, ±v_s are the counterstreaming velocities, and T_e is the electron temperature.