One-dimensional air temperature measurements by air resonance enhanced multiphoton Ionization thermometry (ART)

Posted on 12.05.2022 - 21:55
In this work, a detailed calibration study is performed to establish non-intrusive one-dimensional (1D) rovibrational temperature measurements in unseeded air, based on Air Resonance enhanced multiphoton ionization Thermometry (ART). ART is generated by REMPI (Resonance Enhanced Multi-Photon Ionization) of molecular oxygen and subsequent avalanche ionization of molecular nitrogen in a single laser pulse. ART signal, the fluorescence from the first negative band of molecular nitrogen, is directly proportional to the 2-photon transition of molecular oxygen C³Π (v=2) ← X³Σ (v’=0), which is used to determine temperature. Experimentally, hyperfine structures of the O₂ rotational branches with high temperature sensitivity are selectively excited through a frequency-doubled dye laser. Electron-avalanche ionization of N₂ results in the fluorescence emissions from the first negative bands of N₂+ near 390, 425, and 430nm, which are captured as a 1D line by a gated intensified camera. Post processing of the N₂+ fluorescence yields a 1D thermometry line that is representative of the air temperature. It is demonstrated that the technique provides ART fluorescence of ~5cm in length in the unseeded air, presenting an attractive thermometry solution for high-speed wind tunnels and other ground test facilities.

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McCord, Walker; Clark, Aleksander; Zhang, Zhili (2022): One-dimensional air temperature measurements by air resonance enhanced multiphoton Ionization thermometry (ART). Optica Publishing Group. Collection. https://doi.org/10.6084/m9.figshare.c.5967768.v2
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