Effect of frequency on microplasmas driven by microwave excitation

Abstract

The effect of excitation frequency on the breakdown voltage of a microwave (mw) microdischarge and its steady-state plasma parameters is studied by the self-consistent one-dimensional Particle-in-Cell Monte Carlo collisions model. It is found that for microdischarges in which the electron wall losses are significant, an increase in the mw frequency results in a decrease in the breakdown voltage. For conditions in which the electron wall losses become negligible, an increase in the frequency does not influence significantly the breakdown voltage. At the same time, for both regimes, the increase in the frequency results in an increase in the steady-state plasma density. The analysis of the steady-state plasma parameters have shown that the dominant electron heating mechanism is the Joule heating while the stochastic heating is negligible. Also, it is found that the electron energy distribution function consists of two electron groups, namely, slow and fast electrons. The presence of fast electrons in the plasma bulk indicates the non-local nature of microwave excited microdischarges.

Plasma generation by dielectric resonator arrays

“…The computed peak electric field at breakdown as a function pd is shown in figure 3(b). The breakdown field is the order of 10 4 V m −1 which is consistent with the microwave breakdown determined in a carefully controlled parallel plate geometry [17] and recent simulations in microgaps at high pressure [18]. Finally, we calculate the magnitude of the microwave breakdown voltage by integrating the breakdown electric field along the shortest line between the two resonators.…”

Microplasma thruster powered by X-band microwaves

“…X-band microwaves have been employed to generate highdensity, high-temperature plasmas under electron cyclotron resonance conditions at low pressures (∼10 −5 -10 −4 Pa) for use of highly charged ion and short wavelength radiation sources; [72][73][74] and a few studies have been concerned with plasma discharges at higher and atmospheric pressures (∼1-50 kPa) where the plasma is highly collisional. 75 Microwave frequency effects on plasma discharges have recently attracted much attention to generate higher density nonthermal microplasmas at atmospheric pressures, [76][77][78][79][80] from the viewpoint of a fundamental interest in plasma physics/ chemistry as well as their applications such as materials FIG. 1.…”

“…processing, chemical synthesis, and plasma medicine. However, these studies of microplasmas driven by X-band and much higher frequency microwaves have focused on microstrip-based implementations with interelectrode gaps, [76][77][78][79][80] where electrons and ions are assumed to be confined in the gap by oscillating electric fields, which results in particle losses to the walls to become negligible, and thus leads to an increase in plasma density. 79 Little research has been conducted on surface waveexcited microplasmas as well as SWPs of conventional scale driven by X-band microwaves.…”

Characteristic plume morphologies of atmospheric Ar and He plasma jets excited by a pulsed microwave hairpin resonator

“…A more sophisticated simulation model is still in training and reorganizing from our previous models. Maybe a self-consistent fluid model [31,32,[44][45][46][47][48][49] or a particle-in-cell model plus Monte Carlo calculator (PIC/MCC) [22,[50][51][52][53][54][55][56] could indicate much more physical information for hairpin resonators.…”