Plasma Profile Measurements for Laser Fusion Research with the Nike KrF Laser*

The grid image refractometer of the Nike laser facility (Nike-GIR) has demonstrated the capability of simultaneously measuring electron density ($n_e$) and temperature ($T_e$) profiles of coronal plasma.\footnote{J. Oh, et al, Rev. Sci. Instrum. 86 (2015) in press.} For laser plasma instability (LPI) research, the first Nike-GIR experiment successfully measured the plasma profiles in density regions up to $n_e \sim 4 \times 10^{21}$ cm$^{-3}$ (22\% of the critical density for 248 nm light of Nike) using an ultraviolet probe laser ($\lambda_p = 263$ nm). The probe laser has been recently replaced with a shorter wavelength laser ($\lambda_p = 213$ nm, a $5^{th}$ harmonic of the Nd:YAG laser) to diagnose a higher density region. The Nike-GIR system is being further extended to measure plasma profiles in the on-going experiment using 135$^\circ$-separated Nike beam arrays for the cross-beam energy transfer (CBET) studies.\footnote{J. Weaver, et al, Anomalous Absorption Conference, Ventura, CA, June 14-19, 2015.} We present an overview of the extended Nike-GIR arrangements and a new numerical algorithm to extract self-consistant plasma profiles with the measured quantities.