Observation of Nonquasistatic Plasma Surface Waves

Abstract

Surface waves have been launched from a waveguide onto a glass‐clad plasma column of moderate size (2πR≈λ₀) in order to test the validity of quasistatic analysis when the small‐column condition (2πR≈λ₀) is not satisfied. Resonances were observed in an open microwave cavity, and dispersion of both the circularly symmetric surface wave and the dipole surface wave has been determined from experimental data. The two waves exhibit regions of backward‐wave and forward‐wave propagation. The observed positive slope of the dipole mode dispersion curve near ω/k_z=c is contrary to the predictions of quasistatic analysis and is shown to agree quantitatively with the results of a more rigorous analysis.