CHARACTERIZATION OF PLASMA IN AN INDUCTIVELY-COUPLED HIGH-DENSE PLASMA SOURCE

An inductively coupled radio-frequency plasma source was characterized by optical emission spectroscopy, microwave interferometry and electr ical measurements. The plasma source works like a transformer. The pla sma acts as a single-turn secondary winding of a transformer. The prim ary current produces a magnetic flow in the transformer core resulting in a closed-path axial electrical held in the toroidal discharge tube . The source was found to be capable of generating high plasma densiti es. Electron densities were measured by microwave interferometry. Maxi mal mean electron densities of 4.2 x 10(18) m(-3) in helium at 600 mTo rr and 3.6 x 10(18) m(-3) in oxygen discharges at 400 mTorr were detec ted. Mean collision frequencies of electrons were determined by electr ical measurements. Optical emission spectra showed strong radial varia tions in electron density in both discharges. In oxygen discharges the radial variation of the extent of dissociation was small compared to the variation of the electron density.