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Description
Non-thermal atmospheric pressure plasma jets (APPJs) driven by noble gases are investigated for plasma medicine due to their ability to generate reactive species at near-ambient temperatures. However, achieving stable operation while maximizing reactive species production requires understanding breakdown dynamics, discharge stability, power coupling, and plasma–air interaction mechanisms.
This work presents the design, multiphysics modelling, and experimental validation of a coaxial Dielectric Barrier Discharge (DBD) reactor operating with argon at atmospheric pressure. A one-dimensional axisymmetric COMSOL model was developed to couple Poisson’s equation, electron transport equations (drift–diffusion approximation), heavy-species conservation, and laminar gas flow, incorporating argon excitation and ionization kinetics. This reduced-order approach enabled efficient computation of discharge structure and species evolution while preserving essential non-equilibrium physics.
Simulations predict a peak electron density of 1.4 × 10¹⁷ m⁻³ and an electron temperature of 3.7 eV, corresponding to a strongly non-equilibrium regime (Te ≫ Tg). The spatial distribution of electron density indicates sheath formation near the dielectric interface and a quasi-neutral plasma core, consistent with DBD glow characteristics. Power deposition analysis confirms efficient volumetric excitation without transition to filamentary or arc modes within the stable operating window.
Experimental characterization (4.0–5.0 kV, 1–10 kHz) demonstrates a broad glow-discharge stability region in argon. The discharge maintains laminar plume propagation up to 10 kHz before transitioning to thermal arcing due to increased current density and gas heating. Optical Emission Spectroscopy (OES) confirms dominant atomic argon lines at 696–811 nm, indicating strong excitation of 4p–4s transitions. Additionally, emission bands in the 308–410 nm region reveal secondary species formation via Penning ionization and excitation of ambient N₂ and H₂O, highlighting the role of plasma–air mixing in reactive oxygen and nitrogen species (RONS) generation.
An optimal condition was identified at 5 kHz and 4.5 kV, where maximum power coupling efficiency coincides with discharge stability. Under these conditions, the plasma plume extends 36 mm with gas temperature remaining below 50 °C, confirming preservation of non-thermal characteristics suitable for biomedical exposure.
This framework provides a physics-based method for defining the Safe Operating Area (SOA) of atmospheric DBD plasma jets and offers guidance for scaling APPJs for plasma-medicine applications.