Multipole resonance probe measurement in plasma

Abstract

Active plasma resonance spectroscopy (APRS) is one of the interesting methods which could avoid plasma contamination problem occurs in a conventional Langmuir probe measurement. It is because the probe conductors are covered by a dielectric material. The APRS probe can be of any shape. A multipole resonance probe is a hemisphere APRS probe since a sphere imposes the simplest way to find an analytical solution by solving the Laplace equation in the spherical coordinates with the azimuthal symmetry. In this study, the APRS probes in the hemisphere, microstrip, and parallel rod shapes were constructed. Plasma density was obtained by using the probe that is connected with a network analyzer to locate the match frequencies in the reflection coefficient spectrum. The match frequencies of different probe shapes were then calibrated with the plasma density obtained by Langmuir probe measurement. Our experiments showed that the constructed probes respond with the change in plasma. For the hemisphere probe, the results of the calibrated and the mathematically analyzed results were compared. Our study showed that the plasma density from the mathematical model is approximately the second order of magnitude away from that of the Langmuir probe.