HIGH-POWER OXYGEN INDUCTIVELY COUPLED PLASMA DISCHARGE FOR SPECTROCHEMICAL ANALYSIS

The diagnostics of a high-power (4.2 and 3.2 kW) atmospheric-pressure oxygen inductively coupled plasma (at 27 MHz) reveals spatial temperature fields corresponding to a hot plasma discharge reaching 10200 K surrounded by a relatively low (> 4000 K) but uniform temperature zone. The electron number density is 1014 to 1016cm-3 in a zone above the induction coil. Steep thermal gradients exist at a radius of about 3.6mm corresponding to the edge of the luminous discharge. Measured radial temperature distributions from the absolute 0 I 715.7 nm and 615.8 nm line intensities are compared with theoretically calculated distributions. The plasma temperature field is shaped by the oxygen transport properties. The calculated equilibrium oxygen plasma composition indicates high (1018 cm-3) atomic oxygen concentrations, although the analytical performance should not be limited by oxide formation in the regions of the discharge above 6000 K. Nebulization of water into the oxygen discharge increases the temperature of oxygen plasma and the oxygen emission intensities. © 1990.