Modeling vacuum and gaseous breakdown in dielectric-loaded systems

Summary form only given. Particle-in-cell (PIC) tools and analysis techniques are developed and used to study contributions to breakdown in vacuum through atmospheric pressure for various gases in DC systems loaded with angled dielectrics. Gaseous species include, separately, stationary H₂, Ar, and air. Weakly collisional discharges from vacuum through low pressure have similar behavior as a function of pressure and are well-characterized by distribution metrics for secondaries, e.g. average emission coefficient and emission-energy mode. Higher pressures will be shown to exhibit coupling effects from volume and surface-charge buildup at boundaries. Outgassed species are included for select simulations and penetrate deeply into the system via diffusion, particularly at lower pressures, leading to earlier onset and enhancement of space-charge effects, primarily through enhanced ionization.The effect of seed-currents will also be discussed. It will be shown that the conditions necessary for breakdown are independent of the seed characteristics; however, the temporal evolution of breakdown can be markedly affected by the seed conditions. Beam-like sources, unaffected by local potentials, are used as benchmark seeds that allow unambiguous characterization of either multiplicative or dark-current regimes. Distributed, self-consistent sources provide additional upstream quenching mechanisms; a seed model is developed from [1] as a characteristic example. A novel extension of the work done in [2] covering susceptibility of dielectric-loaded discharges is applied to the DC discharges studied here. Limits for susceptibility are developed from considerations of multiplicative characteristics in DC by applying the theory in [3] to simplified dynamics via low-order expansions of particle lifetime and range for near-surface particles when appropriate.