Pulsed microplasmas generated in truncated paraboloidal microcavities: simulations of particle densities and energy flow

Abstract

Microplasmas generated within cavities having the form of a truncated paraboloid, introduced by Kim et al (2009 Appl. Phys. Lett. 94 011503), have been simulated numerically with a two-dimensional, fluid computational model. Microcavities with parabolic sidewalls, fabricated in nanoporous alumina (Al2O3) and having upper (primary emitter) and lower apertures of 150 µm and 75 µm in diameter, respectively, are driven by a bipolar voltage waveform at a frequency of 200 kHz. For a Ne pressure of 500 Torr and 2 µs, 290 V pulses constituting each half-cycle of the driving voltage waveform, calculations predict that ∼10 nJ of energy is delivered to each parabolic cavity, of which 26–30% is consumed by the electrons. Once the cathode fall is formed, approximately 65% and 8% of the input energy is devoted to driving the atomic ion and dimer ion currents, respectively, and the peak electron density of ∼6 × 1012 cm−3 is attained ∼90 ns following the onset of the first half-cycle (positive) voltage pulse. Specific power loading of the microplasma reaches 150 kW cm−3 and the loss of power to the wall of the microcavity drops by as much as 24% when the excitation voltage is increased from 280 to 310 V. The diminished influence of diffusion with increasing pressure is responsible for wall losses at 600 Torr accounting for <20% of the total electron energy.

Investigation of surface boundary conditions for continuum modeling of RF plasmas

“…The detail of this derivation is given in Appendix A. Eq. ( 25) is identical to the SEE BC equation used in the previous works 24,42,43 .…”

“…This BC includes the effect of the SEE by ion impact. Here, the formulation given in the previous works 24,42,43 are used to apply this BC. The ion flux at the boundary is identical to Eq.…”

Review of numerical simulation of atmospheric-pressure non-equilibrium plasmas: streamer discharges and glow discharges

“…By a scheme similar to that of Hagelaar et al, 61) a boundary condition for the electron energy density flux was proposed by Lee et al 62) as follows:…”

Different ionization mechanisms in pulsed micro-DBD’s in argon at different pressures

“…Seo [22] et al utilized a two-dimensional fluid simulation of microplasma to investigate the temporal history of the spatially resolved electron and ion number densities in response to an ac-driven voltage waveform, and discovered the dependence of plasma development on the pd values. Lee [23] et al calculated the particle densities and energy flow in the microcavities with parabolic sidewalls that fabricated in nanoporous alumina. Some simulation works [24][25][26][27][28] have been carried out to investigate the mechanism of ionization wave propagation, however, few simulations are reported to investigate the ionization wave propagation in micro-discharge, especially at different circumstances, such as pressure dependent.…”