Structure of direct-current microdischarge plasmas in helium

Abstract

A one-dimensional, self-consistent, continuum model is used to elucidate plasma phenomena in a parallel-plate dc microdischarge with a 250 μm gap at a pressure of 250 Torr. The microdischarge is found to have a bulk plasma region and a cathode sheath region with sizes that are comparable. Depending on the discharge current densities, peak electron densities of order up to 1014 cm−3 are predicted. Electron temperature of several eV are predicted within the cathode sheath while temperatures between 2 and 3 eV are observed in the bulk plasma. Gas temperatures of the order of 1000 K are predicted, emphasizing the importance of gas heating phenomena in dc microdischarges.

Electron and Ion Kinetics in a DC Microplasma at Atmospheric Pressure

“…While He + ions are dominant near the cathode, fluid models [2], [4] indicate that dimer ions (He 2 + ) are the dominant positively charged species near the anode. The shift of the total plasma density to a position that is close to the anode that is reported in [2], however, seems counterintuitive and has not always been observed [4]. Such a shift may be due to ion production from metastable states that are not considered in the PIC simulation.…”

Nanosecond, repetitively pulsed microdischarge vacuum ultraviolet source

“…[1][2][3][4][5][6][7][9][10][11][12][13][14][15][16]19,22 Microdischarges have been explored for micro-propulsion, 5 microfabrication, 6 micro chemical reactors, 7 along with many other applications. One unique characteristic of MDs is the shifted electron energy distribution function (EEDF), resulting in an increased population of higher energy electrons.…”

Self‐Consistent Simulations of Plasma and Gas Dynamics in Microplasmas with Metallic and Dielectric Electrodes

“…Furthermore, in small‐space discharges, the energy transfer to the neutral gas as a result of collisions between charged and neutral particles, induces energy gradients and can in turn induce a convective movement of neutral particles. The flow pattern and profile of the neutral gas were also shown to be significantly different in small geometries as compared to larger configurations 16–19. Interestingly enough, this gas heating and convective motion of neutrals8, 16–19 can initiate heterogeneity of the neutral density, N .…”