Spectroscopic characterization of a two-dimensional array of microwave-generated microplasmas

Summary form only given. We present spatially-resolved spectroscopic measurements of a two-dimensional array of microplasmas operating in atmospheric-pressure argon. Each microplasma is generated on the end of a microwave-frequency resonator consisting of a quarter-wavelength long stripline-like transmission line. The resonator array is powered from a single amplifier. Improvements to the previous array design¹, including embedding reference electrodes into the array structure and reducing the spacing between rows of resonators, allow for robust and efficient operation in rare gases at pressures up to atmospheric. Power efficiencies exceed those for similar linear arrays and single resonators, likely due to coupling between nearby microplasmas. We estimate neutral gas temperatures in the produced microplasmas by fitting theoretical molecular spectra to observed emission from impurity species. Typical results range from room temperature up to 800 K. These temperatures are used to estimate electron densities via determination of Stark broadening of the H_β line at 486 nm. Electron densities typically exceed 10¹⁴ cm^-3 in argon. Limitations of emission spectroscopy techniques on highly non-uniform filamentary discharges are discussed.