PRODUCTION OF LARGE-DIAMETER PLASMA BY USING MULTI-ANNULAR ANTENNA FOR ELECTRON-CYCLOTRON-RESONANCE

A large diameter uniform plasma is produced by electron cyclotron reso nance using multi-annular antenna as a microwave launcher with permane nt magnets. The uniformity of the ion saturation current is +/-10% for 280 mm diameter at 100 mm from a single annular antenna, where the el ectron density of the uniform area exceeds the cut-off density for the microwave frequency. By using a threefold annular antenna consisting of four rings of magnets, an ion saturation current of more than 5 mA cm(-2) is obtained over an area almost 300 mm in diameter at 40 mm fro m the antenna. It is demonstrated by calculation that both the uniform ity and density can be improved by the control of microwave power dist ribution.