Cascaded parametric amplification of lower hybrid waves using electron Bernstein waves

Abstract We propose a novel method for generating high-harmonic ion Bernstein waves in the lower hybrid (LH) range of frequencies—here referred to as LH waves—in the confined region of magnetized plasmas. The method relies on stimulating a cascaded parametric down-conversion of electron Bernstein waves (EBWs). In addition to a primary microwave source (such as a gyrotron), cascaded parametric amplification (CPA) of LH waves requires either a low-power EBW or a low-power LH wave for seeding. The CPA mechanism is demonstrated with a 1D Wentzel-Kramers-Brillouin (WKB) model, which is benchmarked against a fully kinetic particle-in-cell simulation, showing quantitative agreement. Our calculations predict attainable conversion efficiencies to LH waves around 10% in steady state, exceeding the Manley–Rowe limit more than tenfold. The CPA mechanism could provide a path for LH wave generation in magnetic confinement fusion reactors that rely on microwaves in the electron cyclotron range of frequencies for plasma heating.