Estimation of Plasma Parameters using Radio-Frequency Resonance Technique

Abstract

Numerous workers have studied rf resonance probe under the condition ν m ≪ω ep , i.e. under collisionless condition, where ν m is angular collision frequency and ω ep is angular plasma frequency. In the present paper, the interaction of rf signal with a back diffusion type plasma has been studied without neglecting collision frequency. The problem has been discussed theoretically under this condition, and the derivation yields two expressions for which impedance is minimum. To verify the result experimentally, a rectangular plasma chamber is designed and fabricated, where electron density can be changed without changing the discharging potential and vacuum conditions. From the experiment two resonance peaks are obtained in the I – f 2 curve ( I : current and f : applied frequency) corresponding to the two minimum impedance conditions, from which plasma parameters like electron density, collision frequency and electron temperature have been estimated.