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

Summary form only given: Wave-cutoff method using microwave provides capabilities for diagnostics of various processing plasmas, and can give the precise absolute electron densities. In this study, pressure limitation of electron density measurement using a wave- cutoff method is presented. As gas pressure increases, the wave-cutoff signal disappears. The disappearance of signal happens when the electron-neutral collision frequency is over the plasma frequency. At that time, the electron motion cannot catch up to the movement of the electromagnetic wave, and the electromagnetic waves begin to penetrate into plasma. In result, the wave-cutoff signal disappears. In this work, the pressure limitation of wave-cutoff method is shown by using an impedance analysis of the probe system, and using commercial microwave simulator, CST Micro-Wave Studio.