COLLISION AND INTERPENETRATION OF PLASMAS CREATED BY LASER-ILLUMINATED DISKS

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-mu-m laser at an intensity of 10(14) 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 10(20) cm-3. Spectroscopic measurements suggest a coronal electron temperature of approximately 800 eV and an ion temperature of approximately 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.