Abstract

A cavity-enhanced Thomson scattering (CETS) diagnostic has been developed to perform electron density and temperature measurements in low-density weakly ionized discharges. The diagnostic approach is based on generating a high-power beam in an optical build-up cavity and using the beam as a light source for Thomson scattering from plasma housed within the cavity. In our setup, a high-power ($\sim 5\mathrm{W}$) fiber laser at 1064 nm allows an intra-cavity power of 11.7 kW in a two-mirror cavity for measurements in the plume of a BaO hollow cathode discharge. A study of plasma density and temperature was performed at various operating conditions. Electron densities and temperatures in the range of $\sim {10}^{12}{\mathrm{cm}}^{-3}$ and $\sim 3\mathrm{eV}$ were measured, respectively. The high signal-to-noise ratio (SNR) of the present measurements ($\mathrm{SNR}=1100$) suggests the ability to measure significantly lower density plasmas in the range of $\sim 3\times {10}^9$ to $3\times {10}^{10}{\mathrm{cm}}^{-3}$, thereby extending current laser Thomson scattering diagnostic capabilities.

© 2018 Optical Society of America

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