Modeling of gas breakdown and early transients of plasma evolution in cylindrical all-dielectric resonators

Abstract

We report on the computational modeling of gas break down and evolution of plasma in an all-dielectric resonator structure. Two cylindrical dielectric resonators (DR) of diameter 25 mm with material relative permittivity of 172.5 separated by a 1 mm gap are observed to resonate in a strong constructive interference mode (CIM) at 1.47 GHz. The electric fields in the gap between the DRs are amplified to about 30 times the incident wave strength which leads to gas breakdown in argon at 10 Torr. The species densities in the bulk of plasma rise primarily due to the wave power addition into the plasma. As the species densities rise above 1017 m−3, the bulk plasma acts as a lossy material and the wave experiences significant damping through collisional losses. As plasma densities in the bulk rise to around 1018 m−3, the wave is damped significantly in the bulk, and a surface plasmon polariton (SPP) wave mode develops at the interface of plasma sheath and the DR surfaces. These surface waves are initiated due to a thin negative permittivity region of the plasma in the vicinity of the DR surface. The quasi-steady state operation of the resonator system depends on the propagation of the damped CIM in the bulk regions of the plasma, the SPP waves in the sheath region and the slower ambipolar diffusion process in plasma. Gas temperature rise in plasma is found to be small throughout the time scales considered and electrostatic fields are found to play an equally important role for large plasma densities in the sheath regions.