Development of rf plasma generators for neutral beams

The development of low frequency (1–2 MHz) rf plasma generators for high power neutral beam applications is summarized. Immersed couplers from one to three turns were used. Acceptable plasma profiles, ≤15% max/min, were obtained in a variety of field‐free, magnetic bucket and magnetic filter‐bucket sources, with 10×10 or 10×40 cm extraction areas. Hydrogen beam properties were measured with a 7×10 cm accelerator operated at 80 kV. Atomic fraction and power efficiency were at least as high as with arc plasmas in similar chambers. The potential advantages of an rf plasma source are: ease of operation; reliability; and extended service lifetime.