APPLICATION OF DIAGNOSTICS TO CHALLENGING DISCHARGE ENVIRONMENTS We have hosted collaborators to utilize laser-collision induced fluorescence (LCIF) diagnostics developed through PSC support. Neil Arthur (John Foster): Biased cusps for plasma flow modification. Amanda Lietz (Mark Kushner): Atmospheric pressure plasma jets in humid environments. LCIF Diagnostic Multi-cusp plasma Plasma jets 2.3% H2O shroud Pure He ne (Peak: ~ 1013 e/cm3) LIF Measured electron densities  Collaborative interactions leverage unique capabilities to address challenges. DOE Plasma Science Center Control of Plasma Kinetics HIGHLIGHT June 2018 1

GAS TEMPERATURES AND ELECTRON DENSITIES IN 13 MHz Ar AND He ATMOSPHERIC PRESSURE PLASMA JETS (APPJs) Ar or He flow through a quartz tube with a 13 MHz powered needle electrode, grounded outer ring electrode (Bruggeman design). Tgas measured by fitting a model to N2 (CB) emission from background air (top figure). ne measured by Stark broadening of H emission from trace added H2. Measurements along jet axis as a function of distance from the nozzle, bounded by a substrate or no substrate. Tg is higher for He than for Ar, and nearly independent of distance (bottom figure). ne, cm-3(not shown) = 1-5x1013 (Ar); 5x1012 (He). Figure: (top) N2 (CB) optical emission bands (solid points) in Ar and He APPJs, and model fits with adjustable parameter Trot(C) = Tg; (bottom) Tgas vs distance from nozzle with quartz substrate present (Ar, He), or not present (He). DOE Plasma Science Center Control of Plasma Kinetics HIGHLIGHT June 2018 2