Effect of mass spectrometric sampling interface on the fundamental parameters of an inductively coupled plasma as a function of its operating conditions: Part II. Central-gas flow rate and sampling depth

The fundamental parameters of an inductively coupled plasma (ICP) were measured by means of Thomson and Rayleigh scattering to study the changes induced by the presence of a mass spectrometer (MS) sampling cone. The electron number density (ne), electron temperature (Te), and gas-kinetic temperature (Tg) upstream from the mass spectrometer sampler were followed while the central-gas flow rate and MS interface sampling depth were varied. The gas-kinetic temperature was found to decline at greater central-gas flow rates, an effect that was elevated in the presence of the MS interface. As the MS interface was brought closer to the ICP load coil, decreases in upstream plasma Tg ensued. Overall, changes in the upstream fundamental parameters caused by the presence of the MS interface were found to depend on operating conditions.