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.

Modeling of atmospheric gas-stream processing using a microwave excited all-dielectric resonant plasma discharge

“…Thus, the timescales of the evolution of electrostatic fields are comparable to the plasma generation timescales and hence this field is primarily responsible for transport of the electrons and charged species in the plasma. This approach, of decomposing the total electric field and its contributions based on evolution timescales has been used before for simulation of microwave driven plasmas [32] and capacitively coupled plasma (CCP) discharges [33] and is accurate for high frequency incident waves [22,24,34].…”

“…This work is motivated by the experiments of Dennison et al [17] where they studied a linear array of cylindrical all-DRs to generate an argon plasma breakdown by exploiting resonant modes in the microwave regime. We have previously modeled this system and studied the breakdown phenomena in the intercylinder gap and the early plasma development phase [22].…”

“…We have recently performed computational modeling studies of plasma generation in a variety of resonant microwave systems including two-cylinder DRs [22], split ring resonators [23], and corrugated metal-dielectric cavities [24]. However, these studies are mostly limited to simple gases at lowpressures with a focus on studying the initial breakdown phase of plasma formation.…”

“…However, these studies are mostly limited to simple gases at lowpressures with a focus on studying the initial breakdown phase of plasma formation. However, once the plasma is formed the electromagnetic characteristic of the system is altered and can cause a shift in the resonant frequencies [22,25]. The electromagnetic nature of the system with the plasma is therefore expected to be significantly different from that during the initial plasma breakdown phase.…”

Surface plasma discharge generated by spoof surface plasmon polariton excitation: a computational modeling study

“…Next the plasma model equations are solved simultaneously with the EM wave equations. Previous work by [34] have shown a successful implementation of the plasma-wave coupled model and illustrated the transients of micro-plasma generation by cylindrical alldielectric resonators. For this work, the EM wave module has been parallelized and solved with the plasma governing equations to study larger scale problems.…”