The relation between internal and external parameters of a spectrochemical inductively coupled plasma

The excitation kinetics in a spectrochemical plasma are governed by the electron density n_e, electron temperature T_e, and heavy particle (gas) temperature T_h. Therefore, knowledge of these ‘internal’ plasma parameters is important for an understanding of the relation between the sample concentration in the plasma and light emission. Because of the small size of the plasma, the internal plasma parameters are related rather directly to the ‘external’ operational parameters of the plasma, such as the plasma dimensions, power density, and pressure. This relation is established by the various particle and energy balances, and can be used to estimate the internal plasma parameters and predict trends for a change in the operational parameters. In the present work, this approach was applied to spectrochemical inductively coupled plasmas under various gas-flow, gas-composition, and plasma-power conditions, and validated by Thomson scattering experiments. The measured values and trends of the internal plasma parameters are in close agreement with those expected on the basis of the operational parameters of the plasma.