Helicon-Drift-Current Interaction in a Solid-State Plasma Waveguide

Abstract

Theoretical predictions indicate that a drift current in a single-component plasma should produce a Doppler-type shift in the helicon-wave velocity. In this paper we report the observation of such an interaction between a traveling helicon wave in a solid-state plasma waveguide and a drift current in the same plasma. The wave-current interaction was observed for frequencies in the low megacycle range. The plasma waveguide was a bar of $n$-type PbTe at 1.8\ifmmode^\circ\else\textdegree\fi{}K through which dc drift-current densities up to 2500 A/${\mathrm{cm}}^{2}$ were passed. The observed interaction is in reasonably good agreement with theory, provided waveguide and damping effects are taken into account. Waveguide effects are shown to reduce the magnitude of the interaction. Collision damping of the helicons complicates the interpretation of the data by introducing an apparent asymmetry into the measured effect of the drift current for directions parallel and antiparallel to the helicon propagation direction.