Using lasers to understand properties of plasmas out of thermal equilibrium

What is it about?

Thomson scattering refers to a plasma diagnostic in which a laser beam is used to probe a plasma and infer its properties. Most existing methods of analyzing Thomson scattering data assume that the plasma is in thermal equilibrium; however, many interesting laboratory plasmas relevant to astrophysical systems and fusion devices are significantly out of thermal equilibrium, limiting the ability of traditional Thomson scattering techniques to fully understand their behavior. In this paper, we discuss the difficulties involved in using Thomson scattering to infer properties of plasmas out of thermal equilibrium, and present a set of numerical tools which can be used to do this analysis.

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Why is it important?

Improved plasma diagnostics will help us analyze and interpret data in future plasma experiments, which is especially important now given recent advances in nuclear fusion and laboratory astrophysics. Although Thomson scattering is a widely used diagnostic and some past publications have discussed the problem of Thomson scattering from non-thermal plasmas, our work is the first we know of to present the full process, challenges, and requisite numerical tools to enable analysis of this data.