OVERDENSE PLASMAS PRODUCED BY ELECTRON-CYCLOTRON HEATING IN A LINEAR MULTIPOLE

A report is given of characteristics of a plasma produced by electron cyclotron heating (ECH) in a linear multipole (LMP) field configuration. The electron density measured by a 6 mm microwave interferometer reached 2 x 10(12) cm(-3), which corresponds to 30 times the cutoff density for the 2.45 GHz RF source. On the basis of the spatial distributions of electron density, electron temperature and space potential measured with Langmuir and emissive probes, the mechanism of overdense plasma production is discussed. Consideration is also given to steady operation of this configuration, which is essential for practical plasma process applications.