Göttingen 2025 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 4: Low Pressure Plasmas and their Applications I

P 4.3: Hauptvortrag

Montag, 31. März 2025, 17:00–17:30, ZHG006

Force profile and charge estimation of a single particle in the sheath of a dual-frequency CCP — •Jessica Niemann, Viktor Schneider, and Holger Kersten — Institute of Experimental and Applied Physics, Christian-Albrechts-University, Kiel, Germany

Optically trapped microparticles have emerged as valuable non-invasive probes for exploring plasma environments. Using optical tweezers, particle probes can be positioned in regions such as the sheath, which are often inaccessible by conventional diagnostics, enabling precise investigations of local plasma properties. In this study, force profiles acting on trapped microparticles are measured in the sheath of a dual-frequency capacitively coupled plasma (CCP). The discharge is generated by the superposition of two harmonics (13.56 MHz and 27.12 MHz) with a variable phase angle between them. By systematically varying the phase angle, parameters such as the sheath edge position, the maximum electric field force, and the evolution of the particle charge are determined. Additionally, the averaged particle charge is independently estimated by calculating the mechanical work required to move the particle through the sheath, providing a benchmark for evaluating electric field models. Comparisons with models, including matrix sheath theory and Child-Langmuir law, as well as simulation results, reveal good agreement and validate the potential of this approach as suitable diagnostic.

Keywords: Optical Tweezer; Sheath; Microparticle; Dual Frequency Plasma; Particle Charge