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Supersonic, counterstreaming plasmas were produced by ablating plasma from the inside surfaces of two parallel disks made of aluminum and magnesium, respectively, with a 0.53 pm laser at an intensity of lOi W/cm2 for 1.3 nsec. Diagnostics included holographic interferometry, a time-integrated x-ray pinhole camera and a gated x-ray crystal spectrograph with imaging slits. The plasmas interpenetrate for the first half of the laser pulse but stagnate once the electron density exceeds 5 X 102' cmF3. Spectroscopic measurements suggest a coronal electron temperature of -800 eV and an ion temperature of -15 keV in the stagnated plasma. The observations are in good agreement with a two ion fluid model of interpenetrating plasmas in which the dominant slowing down process is ion-ion collisions.

Laser-plasma interaction experiments have been performed with both 1.05-and 0.53-jLim-wavelength light incident on spherical glass targets. Comparisons of hard x-rayspectra and fast-ion energy imply a substantial reduction of hot-electron levels at the shorter wavelength. Increased absorbed energy fractions at the shorter wavelength are in agreement with the expected scaling of inverse bremsstrahlung absorption.

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