Fractional Resonances in Ion Bernstein Wave Heating in a Helicon Plasma Discharge

This work concerns a novel magneto-plasmonic propulsion system. It generates thrust by ejecting magnetically confined, RF heated ions through a magnetic nozzle. Ions are heated through Ion Bernstein Wave Heating (IBWH). We studied IBW heating properties by developing two computational models: firstly, a 3D particle mover, which, with reasonable computational effort, can simulate the behavior of $\sim $10$^{4}$ particles in a field configuration consisting of a uniform background magnetic field and the electrostatic IBW; secondly, a 2D particle-in-cell (PIC) simulation, capable of modeling $\sim $10$^{6}$ particles including their electrostatic and magnetostatic interactions in the corresponding 2D field configuration. While the 3D particle mover predicts heating resonances at all harmonics of the ion cyclotron frequency $\omega _{ci}$, the PIC simulation shows damping and distortion of the full harmonics of $\omega _{ci}$, rendering them impractical for ion heating. The particle mover also predicts heating at 4/3 and 3/2 of $\omega _{ci}$, as anticipated theoretically and reported experimentally. The simulations thus reveal these fractional harmonic resonances as potential candidates for IBWH.