Bremen 2017 – scientific programme

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P: Fachverband Plasmaphysik

P 1: Plasma Diagnostics I

P 1.6: Talk

Monday, March 13, 2017, 10:00–10:15, HS 2010

A simple equation for curling probe plasma diagnostics — •Ali Arshadi and Ralf Peter Brinkmann — Institute of Theoretical Electrical Engineering, Ruhr University Bochum, Germany

The recently invented plasma diagnostic device, curling probe (CP) is an innovative realization of `Active plasma resonance spectroscopy'. The CP is a spiral slot-type antenna. It has been used for accurate measurement of the electron density in low pressure plasmas for materials processing. Because of its planar and spiral structure, the CP is flatly embedded into the chamber wall that minimizes the perturbation. Since a thin layer of Quartz or Kapton covers the CP's metal front, no metal impurity is released during the plasma processing. The CP excites the plasma by a weak RF signal and a network analyzer is used to monitor the power reflection coefficient. Two resonant microwave absorption are observed at specific frequencies between 2 and 5 GHz which are strongly dependent on the electron density and the spiral length. Neglecting the little spiralization effect, this work presents a mathematical model for a `straightened' CP enabling us to determine the electron density for low and high pressure plasmas. A simple and very practical expression for the probe resonance is obtained considering the resonance of a half-wavelength standing wave along the probe length. Good agreement between our computations and the FDTD simulation is shown.