Absorption Spectrum of a Magnetoplasma Dielectric in a Resonant Cavity

Abstract

A simple theory based on plane waves in a cold magnetoplasma is proposed to account for experimentally observed absorption bands for transverse electric waves impinging on a microwave cavity. When the cyclotron frequency is equal to the resonant frequency of the TE111 mode of a cylindrical cavity, the data show a three-fold split of the resonance. The outer frequencies are separated by the plasma frequency, and their geometric mean is the cyclotron frequency. The third resonance is shifted by an amount proportional to the square of the plasma frequency, and it occurs only when the cyclotron frequency is very nearly equal to the empty cavity resonance. The simple theory accounts quantitatively for these three absorption bands, and it is in qualitative agreement with other observations. The experiments were performed on a microwave discharge in argon at a pressure of 150 μ and for a range of plasma frequencies from 1.00 to 2.25 GHz.