Collisionless expansion of pulsed rf plasmas

This paper presents experimental results of the quasi isothermal expansion of a pulsed rf argon plasma (P_rf ≈ 300 W) into a vacuum like environment. A fast (τ_open < 200 μs) gas puffing system prevents significant ionization by energetic electron in the expansion region. Thus, the expansion is dominantly determined by ion dynamics. The spatio-temporal measurement of the ion saturation current indicates a preceding ion front entangled with a strong potential drop. This is in qualitatively good agreement with the predictions by Widner et al and Crow et al. Additionally, there is evidence for a supersonic ion population formed by acceleration of the background plasma by the by-passing ion front.