Analytic Investigation of the Resonance Frequencies of the Curling Probe
Ali Arshadi, Ralf Peter Brinkmann
DPG Frühjahrstagung 2015, Bochum, Germany, 2-5 March (talk)
The term active plasma resonance spectroscopy (APRS) denotes a class of plasma diagnostic methods which utilizes the natural ability of plasmas to resonate on or near the electron plasma frequency: An electrical radio frequent signal (in the GHz range) is coupled into the chamber via an antenna or probe, the spectral response is recorded, and a mathematical model is used to determine plasma parameters such as the plasma density or the electron temperature. The curling probe, is a novel realization of APRS which has many practical advantages. Especially, it can be miniaturized and flatly embedded into the wall of a plasma reactor. Physically, the curling probe can be understood as a ”curled” form of the hairpin probe. Assuming that the spiralization has little electrical effect, this presentation investigates the characteristics of a ”straightened” curling probe by modeling it as an infinite slot-type resonator which is in direct contact with the plasma. The diffraction of an incident plane wave at the slot is calculated by solving the cold plasma model and Maxwell’s equations simultaneously. The resonance frequencies of the probe are derived and good agreement with the numerical results of the probe inventors is demonstrated.