Acetone PLIF, Acetone MTV, and FLEET Measurements of Highly Underexpanded Rarefied Jet Flows

Highly underexpanded jets are a critical part of high-intensity atomic and molecular beam systems that offer low temperatures and high particle flux at the centerline. This study presents a detailed characterization of such jets using a combination of optical diagnostics, and their application to atomic beam formation using a Campargue-type beam source. The diagnostics used to interrogate the flow are acetone Planar Laser-Induced Fluorescence (PLIF), acetone Molecular Tagging Velocimetry (MTV), and Femtosecond Laser Electronic Excitation Tagging (FLEET). Acetone PLIF, acetone MTV, and FLEET measurements of acetone-seeded nitrogen and argon jets confirm the theory and correlations presented in the literature regarding Mach disk location, barrel shock behavior, and centerline velocity profiles. This paper also briefly discusses the effect of acetone seeding on the flow, along with implications for the design of Campargue-type atomic beam sources.