Near-surface nitric oxide concentration measurement in the LENS-XX expansion tunnel facility

A high-resolution tunable diode laser absorption spectrometer setup has been constructed and installed in the LENS-XX hypervelocity expansion tunnel at CUBRC. Previous studies in the literature indicate that the heterogeneous recombination of atomic nitrogen and oxygen into nitric oxide (NO) is an important catalytic pathway in hypervelocity flows. Concentration measurements of NO along the surface of a 4" long, 2" diameter stainless steel cylinder are made using the fundamental vibrational-rotational absorption feature in the mid IR region located at 1835.56 cm^-1. These near-surface measurements are used to describe the catalytic reactivity of the gas-surface interface. Data traces obtained using both a single-element and multi-element detector are discussed.