High-Power Plasma Flows Generated by Nanosecond Vacuum Surface Flashover of Polymeric Materials at 80 kV

Abstract

In this paper, we studied the process of vacuum surface flashover of several polymeric materials initiated by 80-kV, 15-ns pulses with peak discharge current 3 kA. We measured breakdown propagation speed, energy input to the discharge, full ion charge and directional pattern of the plasma flow, the full energy of the particle flow, propellant mass loss, and thrust for polytetrafluorethylene (PTFE), polyethylene (PE), and polymethyl metacrylate (PMMA). In the case of PTFE, we obtained the maximum absolute values of thrust ( $4.7~\mu \text{N}\cdot \text{s}$ ) and the full energy (66 mJ). The values of average mass velocity for all materials lie in the range of 3–7 km/s; values of the average velocity of ions lie in the range of 60–85 km/s. Directional patterns of charge and mass are similar and have distinct symmetry in equatorial and meridional planes. We estimated the temperature of the dielectric surface within a model of energy transfer from the discharge channel to the surface due to thermal conductivity. We showed that at this power level ( $\sim 10^{7}$ W) and short duration of high-current stage of the discharge ( $\sim 10^{-8}$ s), the propellant is consumed mainly during the stage of plasma channel formation.