THE RESPONSE OF THE INDUCTIVELY-COUPLED ARGON PLASMA TO SOLVENT PLASMA LOAD - SPATIALLY-RESOLVED MAPS OF ELECTRON-DENSITY OBTAINED FROM THEINTENSITY OF ONE ARGON LINE

A survey of spatially resolved electron number density (n(e)) in the t ail cone of the inductively coupled argon plasma (ICAP) is presented: all of the results of the survey have been radially inverted by numeri cal, asymmetric Abel inversion. The survey extends over the entire vol ume of the plasma beyond the exit of the ICAP torch; It extends over d istances of z = 5-25 mm downstream from the induction coil, and over r adial distances of +/- 8 mm from the discharge axis. The survey also e xplores a range of inner argon flow rates (Q(IN)), solvent plasma load (Q(SPL)) and r.f. power: moreover, it explores loading by water, meth anol and chloroform. Throughout the survey, n(e) was determined from t he intensity of one, optically thin argon line, by a method which assu mes that the atomic state distribution function (ASDF) for argon lies close to local thermal equilibrium (LTE). The validity of this assumpt ion is reviewed. Also examined are the discrepancies between n(e) from this method and n(e) from Stark broadening measurements. With the err or taken into account, the results of the survey reveal how time avera ged values of n(e) in the ICAP respond over an extensive, previously u nexplored range of experimental parameters. Moreover, the spatial info rmation lends insight into how the thermal conditions and the transpor t of energy respond. Overall, the response may be described in terms o f energy consumption along the axial channel and thermal pinch within the induction region. The predominating effect depends on the solvent plasma load, the solvent composition, the robustness of the discharge, and the distribution of solvent material over the argon stream.