Electromagnetic modeling of a plasma-filled resonator for diagnostics

Cold plasmas with temperatures of less than 1000 K are essential to experiments on laser cooling and magneto-optical trapping [1]. Particularly, Cs and Rb plasmas inside microwave cavity resonators are of interest to the experimenters. Analytical perturbative solutions [1] can provide information about the shifts in resonant frequencies in relation to electron concentrations inside a resonator, thus making first-order plasma diagnostics possible.  In this work, the author presents an approach to numerical simulations of plasmas in microwave resonators, including the effects of photo-ionization and multiple resonant modes, as they develop in time. Time-domain electromagnetic (EM) [2] and particle-in-cell (PIC) methods enable more detailed analysis of  plasma evolution in a resonator. Short-time Fourier transform analysis is applied to the simulated electromagnetic fields. The results show how multimodal cavity resonances are affected by the electron concentrations.  The described model may be useful to explain experimental data in laser beam interactions with cold plasmas.

1. M.A.W. van Ninhuijs, Rev. Sci. Instrum., 92, 013506, 2021.

2. A. Semychayevskyy,, PIER M, 73, 197-203, 2018.