Enhanced performance of atmospheric pressure plasma jets in a DBD by an internal floating electrode inducing optimal local electric field

Electric field strength is critical for generating atmospheric pressure plasma jets (APPJs). In this paper, a capillary copper tube served as an internal floating electrode (IFE) in a dielectric barrier discharge (DBD) with double-ring electrodes to achieve local electric field enhancement. comsol Multiphysics® pre-discharge simulations revealed that the strategic positioning of the IFE configuration—equidistant between the powered and grounded ring electrodes—was critical to achieving an optimal local electric field. This positioning yielded a 5.88-fold increase in the peak electric field strength along the centerline of the quartz tube compared to the conventional double-ring electrode (CDE) configuration. Systematic electrical and optical characterizations demonstrated significant performance improvements of APPJs in IFE-DBD: the number of discharge pulses, jet length, gas temperature, electron density, and spectral line intensities all increased compared to the CDE-DBD configuration, whereas the applied power and electron temperature decreased slightly. Furthermore, the synergistic mechanism between secondary electron emission and local electric field enhancement during APPJ formation was elucidated. This work validates a special electrode design that amplifies the local electric field strength for high-performance plasma generation while preventing continuity in the external electric field distribution to reduce short-circuit risks.