Electron density measurement for microwave-induced atmospheric pressure plasmas using laser deflection method

Summary form only given. A laser beam passing through plasma deflects due to a change in the line-integrated refractive index, which is attributed to an electron density gradient along the chord. By measuring the deflection angle of the laser beam, the electron density was obtained for an atmospheric pressure microwave-induced torch plasma generated in the ambient air. The diagnostic set-up, consisting of a low power He-Ne laser, a four channel segmented position-sensitive photodiode detector, and some relevant optical components, demands modest requirements of laser quality and optics alignments. The measured electron density was compared with that obtained by optical emission spectroscopy based on the measured Stark broadening width of the Balmer H-beta line emitted from the plasma. Both the multi channel deflection method and the optical emission method showed the same order of magnitude (~10¹⁵ cm^-3) electron density values. Comparison of the detailed results will be presented.