Modelling of microdischarge devices: plasma and gas dynamics

Microdischarge devices (MDs) share many properties with their macroscopic counterparts while having unique features resulting from their ability to sustain large current densities and power depositions on a continuous basis at pressures approaching atmospheric. The dynamics of cylindrical, metal–dielectric–metal sandwich MDs sustained in Ar having characteristic sizes of a few hundred micrometres have been computationally investigated using a plasma-transport model which includes gas dynamics. We found that these devices closely resemble negative glow discharges, as they are sustained by, and particularly sensitive to, ionization resulting from secondary electron emission from the cathode. Since these MDs operate on a cw basis with large current densities and power deposition, gas heating and flow dynamics are important considerations in optimizing their electrical and kinetic properties. For example, the formation of excimer species is particularly sensitive to gas heating and rarefaction due to their dependence on three-body formation processes. Scalings of MDs with pressure, current and secondary emission coefficient are discussed.