SFB 1316 – Project A4

Process control in micro atmospheric pressure RF plasma jets by voltage waveform tailoring and customised boundary surfaces

Atmospheric pressure radio frequency microplasma jets (RF µ-APPJ) are frequently used as an efficient source of reactive species at low temperature for a variety of applications ranging from wound healing and sterilization to semiconductor manufacturing. In this project, a combined experimental and computational approach is used to explore the potential of i) voltage waveform tailoring (VWT) and ii) specifically designed boundary surfaces to customize the electron heating dynamics on a ns-timescale in RF µ-APPJs to control and optimize the generation of excited neutrals and reactive radicals. In the experiment, the µ-APPJ is primarily operated in helium with variable admixtures of O2 and/or N2 .

Phase Resolved Optical Emission Spectroscopy (PROES), electrical probes, Two Photon Absorption Laser Induced Fluorescence (TALIF), tunable diode-laser absorption spectroscopy (TDLAS), and other experimental techniques are used to study, e.g., the electron heating dynamics, measure current/voltage, the atomic oxygen density, the Helium metastable density space resolved between the electrodes, etc. The experiments are complemented by a Particle-In-Cell, a fluid-dynamic and a hybrid simulation approaches to provide the basis for a fundamental understanding of the experimental results. Measurements and simulations are performed under identical conditions as a function of the shape and amplitude of the driving voltage waveform, O2 / N2 admixture, electrode materials (including catalytic coatings), and electrode topologies. A4 reveals the basic physics of µ-APPJs driven by tailored voltage waveforms and operated based on customized electrodes.

The results of the project show that VWT provides new concepts to optimize the generation of various reactive species which are highly relevant for many medical and technological applications.