A cutoff probe for the measurement of high density plasma

A cutoff probe is a diagnostic method to find the absolute plasma density through simple means. However, when the cutoff probe is used in the high density plasma diagnostics, the probe can be faced with measurement problems because the high influx energy from the plasma can damage the probe tips, especially for the dielectric material in the vicinity of the probe tips. Because this damage cannot only cause an error in the measurement of electron density but also acts as a contamination source in the plasma, a solution for the cutoff probe damage induced by high influx of ions and electrons is needed for the reliable measurement of the cutoff probe in high density plasma. To solve this problem, we proposed a cutoff probe shielded by the ceramic tube. In this paper, the authors addressed numerous aspects of the Ceramic Shielded Cutoff probe: the problems of the normal cutoff probe for the high density plasma measurement, the validity for the application of probe system to high density plasma measurement, the transmission spectrum characteristics of the cutoff probe, and the experimental/simulation results.

► A cutoff probe shielded by the ceramic tube is proposed.
► The installed ceramic tube helps to reduce the thermal damage of the probe.
► The cutoff frequency is hardly changed by ceramic tube installation.