Determination of electron density distribution using microwave cavities

A microwave cavity resonator oscillating at two modes with different radial electric field distributions (TM020 and TE011) was used for measurements of the radial density profile of the early afterglow period of a neon glow discharge. The ratio of measured frequency shifts of the two resonant frequencies was compared with that calculated for various radial distributions of the plasma density. The effects of the entrance holes and the tube glass walls were excluded by calibration measurements with plasma-simulating dielectric rods. Finally, the time dependence of the radial density profile of the neon afterglow was shown. (J.U.)