Kinetic modeling and experiments of a pulsed-bias plasma in a multipole plasma chamber

Abstract

A pulse of electron timescale applied to a planar electrode immersed in a homogeneous plasma in a multipole plasma chamber (MPC) is modeled using a fully kinetic particle-in-cell (PIC) approach. In the time-explicit PIC simulations, we observed that the ion-sheath expansion is accompanied by electron timescale harmonic plasma oscillations at the sheath edge that decay after applying the pulse. First, we validate our PIC approach by comparing it with previous analytical and semi-empirical sheath expansion studies. Then, we compare our PIC results with experiments conducted in the MPC where similar electron frequency oscillations were excited when an electron timescale pulse was applied to a flat-conductor plate. In both PIC simulations and experiments, we find that the shape of the applied pulse dictates the amplitude of the sheath edge oscillations. In the PIC simulations, we observe that Landau damping has no discernible effect on these oscillations. However, in the experiments, the presence of a hot electron population results in a higher damping of electron oscillations. In both PIC simulations and experiments, the amplitude of the electron frequency oscillations decreases with the applied pulse width and these oscillations disappear for a linear pulse of a longer timescale of tpulse=1 μs (ωpetpulse=178), in the PIC simulations.