Non-Monotonic Electron Temperature Variation in Coaxial Dielectric Barrier Discharge: Combined Simulation and Experimental Study

Experimental measurements and two-dimensional axisymmetric fluid simulations are performed to study coaxial argon dielectric barrier discharge. Oscilloscope measurements capture voltage–charge waveforms and Lissajous figures to resolve cycle-integrated electrical characteristics. Continuous-integration optical emission spectroscopy without phase resolution is used to qualitatively verify metastable argon. As peak voltage rises from 5 kV to 13 kV, the simulated volume-averaged electron temperature displays a pronounced N-shaped trend: it peaks at 9 kV, falls abnormally between 10 kV and 11 kV, and recovers at higher voltages. This non-monotonic variation arises from intra-cycle self-shielding by dielectric surface charges together with power-broadening driven by discharge spatial expansion. Monotonically increasing equivalent capacitance confirms continuous surface charge accumulation, and the simulated inward shift of the high-electron-temperature region validates the emergence of surface-charge-induced reverse electric fields. The discharge maintains a steady filamentary regime across all tested conditions. Because microdischarge filaments occupy only a small portion of the gap, the volume-averaged electron density from simulations is far lower than the peak density within individual streamers. This work elucidates the mechanism underlying the anomalous electron temperature drop at moderate voltages and offers guidance for controlling atmospheric-pressure filamentary DBD.