An Efficient Atmospheric Pressure Resonant Microwave Plasma Line

Atmospheric plasma jets have garnered considerable attention for their diverse applications across fields such as material processing, food, and manufacturing. However, existing plasma jet devices encounter limitations such as bulky design, inefficient power transfer, and jet profile. To address these challenges, microwave resonators, known for their ability to store and focus microwave power, can be employed to facilitate gas breakdown and generate plasma discharge. In particular, an evanescent-mode (EVA) cavity resonator plasma jet has been reported to achieve a power efficiency exceeding 80% with electron density in the range of 10¹⁵ (cm^-3) [1]. These resonators prove instrumental in enhancing the overall performance of plasma jets while enabling more efficient use of power and reducing the physical footprint of the device.

This study introduces a resonant microwave plasma line based on EVA cavity resonator technology. The resonator structure was designed to resonate at a frequency of 2.45 GHz, and when subjected to an input power of 1 Watt, it generates a uniform |E|-field on the order of 10⁵ V/m. To ensure consistent gas flow, the gas flow line is carefully designed by dividing a large inflow into multiple smaller outflows, and optimization techniques are employed to achieve a uniform flow at the output. For precise construction of the resonator, the fabrication process involves CNC machining. Experimental investigations use helium gas flow rates ranging from 1 to 7 slpm and input power levels ranging from 1 to 10 Watts. These experimental parameters provide a comprehensive understanding of the performance and behavior of the resonant microwave plasma line.

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[1] Semnani, A, Kabir, KS 2022 ‘A highly efficient microwave plasma jet based on evanescent mode cavity-resonator technology’, IEEE Trans. Plasma Sci., vol. 50, no. 10, pp 3516-3524.