This study investigates structured light beams and wavelength modulation spectroscopy for advanced plasma diagnostics. Structured light, with its spatial and spatiotemporal structures, enables enhanced signal-to-noise ratios and high-resolution measurements of plasma velocity distribution functions, especially in devices with limited access. The research introduces a confocal Laser-Induced Fluorescence setup using a Laguerre-Gaussian annular laser beam, achieving a spatial resolution of approximately 5 mm at a 300 mm focal distance, with potential to reach up to 1 mm. This advancement could broaden the scope of applications to other diagnostic methods in industrial plasma sources and electric propulsion systems. Additionally, WM spectroscopy, effective in complex plasma environments, measures spectral line profile derivatives, improving spectral resolution and reducing background noise. Findings from confocal measurements with structured light and WM-LIF in an industrial plasma device show that these techniques can provide insights into plasma dynamics not accessible through conventional diagnostics, indicating significant potential for plasma diagnostics applications.
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