Two-plasmon decay of microwaves in low temperature magnetized laboratory plasmas

Abstract

Observations from magnetically confined fusion experiments have in the past decades revealed instances of two-plasmon decay instabilities (TPDIs) between injected 2nd harmonic X-mode waves and trapped upper hybrid (UH) waves near half frequency of the injected wave. We present and compare growth rates of TPDIs computed from reduced analytical models and particle-in-cell (PIC) simulations in low-temperature plasmas, emulating conditions found in more accessible controllable laboratory devices. The growth rates obtained from simulations agree with our modeling, confirming that we can model TPDIs using both analytical models and PIC simulations in low-temperature plasmas. Furthermore, the growth rates are on the order of 0.01 ns−1 to 0.1 ns−1 for injected waves with intensity of 103 W/cm2, which indicates that we can expect to see signals of TPDIs in controllable laboratory plasma devices.