MEASUREMENTS OF INVERSE BREMSSTRAHLUNG ABSORPTION AND NON-MAXWELLIAN ELECTRON VELOCITY DISTRIBUTIONS

Non-Maxwellian (flattopped) electron velocity distributions resulting from inverse bremsstrahlung of intense microwaves are measured directl y for the first time in experiments performed on the UCD AURORA II dev ice. The experiments are performed in the afterglow of a pulsed discha rge plasma that is moderately collisional and sufficiently ionized (ap proximately 1%) that Coulomb collisions are dominant. Langmuir probe m easurements indicate that the isotropic component of the electron velo city distribution is non-Maxwellian in very good agreement with electr on kinetic (Fokker-Planck) simulations.