Abstract: A plasma jet CVD system includes gas injectors and a stand-off ring. The gas injectors have outlet holes preferably flared to approach the expansion angle of the injected jet, thereby keeping the holes substantially free from entrained atomic hydrogen. The injectors are arranged counter-rotational to the swirl of the primary jet, providing a more uniform mixture of hydrocarbons and atomic hydrogen. The stand-off ring provides vents for cooler gases to enter the nozzle, thereby decreasing the overall temperature of the injectors and decreasing the temperature gradient experienced by the injectors, thereby preventing injector cracking. In addition the vents reduce shear, thereby increasing jet velocity and increasing the deposition rate for the coating.

Abstract: A gas injection disc is provided which includes an outer ring and a tubular modular insert which slips into the outer ring. The outer ring is provided with an inner bore, a ring-shaped plenum located around the inner bore, an outer gas sealing surface around the plenum, and two gas feed paths extending from the periphery of the outer ring to the plenum. The gas feed paths are each provided with a gas feed attachment for coupling gas supply tubes thereto. The insert is provided with a plurality of radially aligned injectant holes, an inner gas sealing surface, and an axial bore. The insert is seated in the inner bore of the outer ring such that the inner and outer gas sealing surface face each other with a small gap provided therebetween which enables the insertion of the insert into the inner bore. The insert thereby substantially encloses the plenum, and the injectant holes are aligned with the plenum to receive injectant gases and direct the injectant gases into the axial bore of the insert.