Pressure limitation of electron density measurement using a wave-cutoff method in weakly ionized plasmas

Abstract

Pressure limitation of electron density measurement is presented using a wave-cutoff method. As gas pressure builds up, the electron motion at omega=omega(p) is disturbed by an electron-neutral collision and cannot catch up to the movement of the electromagnetic wave. For this reason, electromagnetic waves begin to penetrate into plasma and the wave-cutoff signal disappears as the gas pressure increases. This was also confirmed by using an impedance analysis of the probe system. The results corresponded well with the measured wave transmission characteristics at the plasma frequency.