The multipole resonance probe: Realization of an optimized radio-frequency plasma probe based on active plasma resonance spectroscopy

A diagnostic concept is presented which enables the simultaneous determination of plasma density, electron temperature, and collision rate in low-pressure gas discharges. The proposed method utilizes a radio-frequency driven probe of particular spherical design which is immersed in the plasma to excite a family of spatially bounded surface resonances. An analysis of the measured absorption spectrum S(ω) of the probe provides information on the distribution of the plasma in its vicinity, from which the values of the plasma parameters can be inferred. In its simplest realization, the probe consists of two dielectrically shielded, conducting hemispheres, which are symmetrically driven by a radio-frequency source, and the excited resonances can be classified as multipole fields, which allows an analytical evaluation of the measured signal. A comparison of the analytical results, 3D-field simulations, and first measurements of a prototype show the functionality of the presented probe concept.