Diagnostics of plasma-liquids systems: challenges and their mitigation

Non-equilibrium, low-temperature plasma is gaining a steady and dedicated following in the bustling inter-disciplinary community interested in plasma science and technology. Small scale, uncomplicated ways of plasma generation in ambient atmosphere and high plasma-induced chemical reactivity make low-temperature plasma very attractive for a wide variety of applications in biomedicine, environmental remediation, and agriculture, prompting new avenues for studying plasma in rich chemical environments and plasma interaction with liquids. Often, these environments pose new challenges for plasma investigation, application of diagnostic methods and interpretation of results.

At this talk I will briefly review the different diagnostics methods for characterization of low-temperature plasma and plasma induced species. I will describe the caveats that are encountered when measuring inherently unstable systems, such as plasma interacting with liquid. Specific example is the correlation of plasma channel dynamics and Thomson scattering measurements. Thomson scattering (TS) technique emerges as popular in the low-temperature plasma community. Thomson scattering is advantageous as its a direct measurement of plasma density and temperature and is routinely used to study low-temperature plasma sources. The TS method has an intrinsic superiority to alternative emission spectroscopy, which constitutes its immediate non-disturbing, widely used optical approach. The detection threshold for TS is lower and it measures electron temperature directly, while analysis of emission lines is related to excitation temperature. In many plasmas TS scattering is the sole possible method capable of plasma characterization. Therefore, the identification of the TS shortcomings is necessary as are approaches to mediate them.