Evidence for the modification of half-harmonic spectral shifts by plasma flow

Abstract

The (3)/(2) ω0 harmonic emission has been observed from a laser-produced plasma using exploding foil targets illuminated by 1.053 μm laser light with a 300 psec square pulse. The shift of the measured wavelength from (2)/(3) λ0 is found to depend markedly on the target thickness. Variation of the flow velocity and thus the Doppler shifts of the wave frequency with target thickness is found to be more important than variation of the electron temperature. Adjusting the measured wavelength by Doppler shifts calculated with flow velocities from simulations brings the measurements from different target thicknesses into agreement. These results indicate that previous predictions of electron temperatures from analyses of half-harmonic spectra from inertial confinement fusion plasmas are up to a factor of 2 too small.