The spatial structure of a low-frequency atmospheric-pressure glow discharge was studied experimentally. The radial current distribution and discharge light emission were simultaneously measured at different phases during the ac voltage cycle. The glow discharge is formed by a radially propagating ionization wave. We also observed discharge regimes with several current pulses per half cycle corresponding to the successive, spatially separated breakdowns.

Langmuir probe measurements of the temporal behavior of the electron distribution function in a low-pressure inductive discharge are presented. The structure of the measured distribution functions suggests that the loss of high energetic electrons to the wall of the discharge chamber is the main energy loss mechanism. Electron-heavy-particle collisions play only a secondary role for the energy loss. The rapid loss of energetic electrons--while low energy electrons remain confined in the space charge potential field--leads to a fast cooling of the electron distribution function. We also present a simple model to describe the evolution of the mean kinetic energy and plasma potential on the basis of a distribution function that is cutoff at energies above the potential electron energy at the wall.

A self-consistent model of capacitively coupled low-pressure rf discharge is formulated. The non-local mechanism of electron heating is considered under simple assumption about the plasma density profile. The transition of electron heating from the plasma body to electrode sheaths is observed. The criterion of a heating mode transition is formulated and expressed in terms of external discharge parameters. The asymptotic solutions for low-and high-current regimes are obtained. The comparison of calculation results with experimental data demonstrates the validity of the proposed model for a wide range of discharge conditions.

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