Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research

Abstract

A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (∼1 ns FWHM) with the intensity of 1.1 × 10 15 W/cm 2. The measured angles and transmissions were processed to construct spatial profiles of electron density (n e) and temperature (T e) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 10 21 cm -3 with the density scale length of 120 μm along the plasma symmetry axis. The resulting n e and T e profiles are verified to be self-consistent with the measured quantities of the refracted probe light.