Current-voltage characteristic of the contact of a plasma with an electrode with a thin dielectric film on the surface

Post-mortem analyses of gap facing surfaces of tungsten tiles of T-10 ring limiter

“…One can hardly expect that particles from plasma may penetrate so deep into so narrow gaps. For explanation of this observation, we suggest a mechanism associated with auto-oscillating discharges, which was proposed in [24][25][26]. These discharges arise between two surfaces (for example the external surface of a W tile and the wall of the tokamak) connected by the magnetic field.…”

“…The condition for the discharge is a high secondary electron-electron emission from one of the surfaces. Enhanced electron emission is typical for thin dielectric films on the surface, and the auto-oscillating discharges were observed on W with a thin oxide film on the surface [26].…”

“…Deposition of carbon films was detected through the entire depth of the gaps including those that were as narrow as 0.1 mm. The effect was explained by auto-oscillating discharges formed on surfaces of the plates, which were analyzed in [26]. This paper is devoted to analysis of gap facing surfaces of two W tiles of the ring limiter of tokamak T-10, which form a gap, where heavy deposits were observed on its entire surface.…”