Diagnostics of Plasma Processes based on Parallelized Spatially Resolved In-Situ Reflection Measurements
Christian Schulz,Jan Runkel, Moritz Oberberg,Peter Awakowicz, Ilona Rolfes
IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES
Vol. 64 Iss. 2
pp. 616 - 623
3D electromagnetic simulations, feedback control, multipole resonance probe, plasma diagnostics
A parallelized in-situ plasma measurement setup, consisting of two Multipole Resonance Probes (MRP), a passive signal divider, and two coaxial cables with different lengths, is presented in this contribution. The combined reflection coefficient of the applied probes is measured, separated in time domain, and evaluated. Here, each MRP is able to measure the spatially resolved plasma electron density via its resonance behavior precisely and quasi-simultaneously. Furthermore, the return loss changes with the collision frequency, which can be detected for each probe. The parallelization and the applied signal processing are confirmed by simulations and combined measurements in CST Schematic as well as by in-situ measurements in an argon plasma. The resulting error is below 1% for the resonance frequency and below 8% for the corresponding return loss. Hence, the input power and gas pressure of a plasma process can be controlled effectively.
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