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 configuratio n. The electron density measured by a 6 mm microwave interferometer re ached 2 x 10(12) cm(-3), which corresponds to 30 times the cutoff dens ity for the 2.45 GHz RF source. On the basis of the spatial distributi ons of electron density, electron temperature and space potential meas ured with Langmuir and emissive probes, the mechanism of overdense pla sma production is discussed. Consideration is also given to steady ope ration of this configuration, which is essential for practical plasma process applications.