Advances in Thomson scattering diagnostics of plasmas used for chemical analysis

Abstract

The use of plasmas for chemical analysis is prevalent and new sorts are continually being explored for potential applications in this field. However, the underlying mechanisms of characteristic processes that occur in plasmas are not completely understood. Free electrons drive chemical reactions, are essential to many plasma inherent processes, and are responsible for sustaining the discharge while governing the kinetic energy transfer between other species. Thomson scattering (TS) is a powerful plasma diagnostic technique for elucidating the fundamental electron parameters of number density, kinetic temperature, and energy distribution function. TS advantages include providing the direct, radially and temporally resolved probing of free electrons, with little-to-no perturbation of the plasma, with no prior assumptions of local thermodynamic equilibrium conditions, and simultaneous electron density/temperature measurements. The aim of this review is to provide a brief explanation of the TS theory and the experimental requirements, as well as highlight selected novel instrumentation advances and insights about chemical analysis plasmas discovered in the most recent TS publications, not previously covered in other reviews.