Abstract: An apparatus for generating large arrays of directed beams containing thermally excited, electrically neutral gas species, including vibrationally excited molecules, free radicals, and atoms, is disclosed. A heated plate in which a designed array of long, narrow channels are formed serves both to activate and collimate the gas species, and separates a high pressure reservoir of reactive gas from an evacuated region which serves as the material processing chamber. Selection of the appropriate reservoir pressure and channel geometry facilitates the thermal excitation of the reactive gas through collisions with hot channel walls, and the formation of directed non-collisional beams which may be readily transported through the evacuated chamber. The heated channel array plate is designed to allow good gas flux uniformity over a large target area by appropriately setting the pitch spacing and aspect ratio of the channels.