One-Dimensional Resonantly Ionized Photoelectron Thermometry Measurements in Supersonic Flow Around a Cylinder

Abstract

In this work, one-dimensional (1D) Oxygen-based Resonantly Ionized Photoelectron Thermometry (O2 RIPT) technique is used for temperature measurements in a M∞ = 4 flow. O2 RIPT resonantly ionizes O2 molecules via (2+1) Resonant Enhanced Multiphoton Ionization (REMPI) process; subsequent ionization via electron-impacted avalanche ionization of molecular nitrogen produces fluorescence emissions from the first negative band of N2 through photoemission deexcitation. The fluorescence emissions of the N2 first negative band occur at Δv0, 390nm; Δv2, 425nm; Δv1, 430nm and are captured by a gated intensified scientific and used for temperature determination via a Boltzmann plot based on the direct relationship with the two-photon line strength. O2 RIPT is used to characterize the free stream static temperature across a 50.8 mm (2”) line, which is compared to isentropic calculations for the Mach 4 flow. Additionally, the thermal field associated with strong compression through a normal shock generated by a blunt 25.4 mm (1”) diameter cylinder is measured.