Abstract: A radiation and regeneratively cooled arc jet device includes improvements designed to provide higher gas enthalpy operation for thin diamond film deposition. A series of circumferentially and axially spaced gas injection holes are provided in the cylindrical inner walls of the arc chamber between a cathode and anode. This arc chamber wall is fabricated from a material having a high thermal shock parameter. The ratio of the spacing of the injection holes within each row as compared to the chamber diameter is set within a specific range. In the circumferential direction, a multiplicity of axial rows of holes are provided and spaced equally about the circumference of the chamber. The annular anode is isolated at the open end of the arc chamber by an insulator having a high thermal shock parameter, to conduct anticipated heat loads without mechanical failure.