Relaxation oscillations of low-frequency Ar/SF₆inductive plasma discharges

A new class of relaxation oscillations has been observed in some inductive plasma discharges operated with low-pressure argon and SF 6 gas mixtures. Some plasma instability seems to develop periodically in the downstream plasma. The nonlinear evolution and the two-dimensional spatial structure of the instabilities are detailed with Langmuir probe arrays and fast video imaging. The measurements show that the instabilities grow in a quasi-spherical downstream layer. The upstream plasma is slightly compressed, while large rarefactions are observed downstream. The upstream plasma then moves slowly downward until the initial plasma profiles are recovered. This article features multimedia enhancements