On the uniformity of an inductively coupled, cylindrical discharge of hydrogen

Summary form only given, as follows. In an RF inductively coupled discharge, the axial extent of the plasma is known to vary with the applied power, the oscillator frequency, and the neutral gas pressure. Applications of such plasmas to materials processing and lighting require a uniform plasma to optimize throughput efficiency and power coupling. To investigate these plasma phenomena, NRL has developed a cylindrical plasma chamber which is transformer coupled to a 13.6 MHz, 10 kW oscillator through a single turn copper strap. The double walled quartz chamber contains axial rods as a capacitive shield to ensure pure inductive coupling. The chamber, which was designed with optical access for plasma/chemistry diagnostics, will be described and initial experiments reported on. The research program also involves 2-D (r-z) numerical simulations of an H/sub 2/ plasma discharge at several Torr pressure. In the models the electromagnetic fields are solved self-consistently with the steady state gas dynamics. A plasma chemistry for the neutral and ionic species H, H/sub 2/, H/sup +/ and H/sub 3//sup +/, is included with multi-species diffusion for the neutral constituents and ambipolar diffusion for the charged components. Electron and neutral temperature equations account for the transfer of energy from the electrons to the neutrals, and finally to the walls. Predictions of the plasma uniformity, magnetic field strengths, and hydrogen Balmer emissions will be presented for various experimental parameters such as power, pressure, inner wall coating, as well as coupling circuit parameters. A simple expression for the axial plasma extent versus these quantities will be presented.