Experimental characterization of a compact microwave plasma source employing three different coupling geometries

Summary form only given, as follows. The recent applications for ECR microwave ion and plasma sources has put demands on their size, low-power and high-density operation. This paper makes an attempt to supplement the past research at MSU concerned with the compact (5-9 cm discharge diameter) ECR ion and plasma sources by experimentally evaluating the output performance of a 7 cm; discharge diameter plasma source operating under three different microwave excitation structures. The plasma source investigated in this paper comprises three sub-assemblies: cylindrical cavity applicator and matching network, quartz discharge chamber, and ECR magnets. The three microwave excitation structures are: 1) side feed probe, 2) end feed loop, and 3) end feed probe. The side feed and the end feed cavity applicator shells are brass and stainless steel with 8.9 cm and 9.8 cm inner diameter respectively. The sliding short end plate and the excitation antenna provide two degrees of freedom in internal tuning for discharge matching and electromagnetic mode selection. The three microwave coupling geometries are able to excite five different electromagnetic coupling modes. Among them are TE/sub 111/, TM/sub 01/ and TEM excitations. A 7 cm diameter and 5.6 cm high cylindrical quartz chamber contains the plasma discharge. An eight pole, arc shaped, permanent magnet array provides the impressed static magnetic field.