Arcjet flow properties determined from laser-induced fluorescence of atomic nitrogen.

Flow property measurements that were recently acquired in the Ames Research Center Aerodynamic Heating Facility arcjet using two-photon laser-induced fluorescence (LIF) of atomic nitrogen (N) are reported. The flow properties, which include velocity, translational temperature, and N concentration, were measured simultaneously over a range of facility operating conditions for N(2)-argon test gas flows in the 30-cm-diameter nozzle. A recent measurement of the two-photon excitation cross section for the 3p(4)D degrees <-- 2p(4)S degrees transition of atomic nitrogen is used to convert the relative nitrogen concentration measurements to absolute values, and a nitrogen flow reactor is used to provide a room-temperature, reference-wavelength calibration of the translational temperature and velocity measurements. When combined with information from facility measurements, an analysis of the flow properties obtained using two-photon LIF of N yields the total free-stream flow enthalpy.