Time-resolved gas thermometry by laser-induced grating spectroscopy with a high-repetition rate laser system

Thermometry using laser-induced grating spectroscopy (LIGS) is reported using a high-repetition rate laser system, extending the technique to allow time-resolved measurements of gas dynamics. LIGS signals were generated using the second harmonic output at 532nm of a commercially available high-repetition rate Nd:YAG laser with nitrogen dioxide as molecular seed. Measurements at rates up to 10kHz were demonstrated under static cell conditions. Transient temperature changes of the same gas contained in a cell subjected to rapid compression by injection of gas were recorded at 1kHz to derive the temperature evolution of the compressed gas showing temperature changes of 50K on a time-scale of 0.1s with a measurement precision of 1.4%. The data showed good agreement with an analytical thermodynamic model of the compression process