  This manuscript presents an ultrafast-laser-absorption-spectroscopy (ULAS)
diagnostic capable of providing calibration-free, single-shot measurements of
temperature and CO at 5 kHz in combustion gases at low and high pressures. A
detailed description of the spectral-fitting routine, data-processing
procedures, determination of the instrument response function, and practical
considerations for imaging ultrashort pulses in the mid-infrared are presented.
The accuracy of the diagnostic was validated at 1000 K and pressures up to 40
bar in a heated-gas cell before being applied to characterize the
spatiotemporal evolution of temperature and CO in AP-HTPB and AP-HTPB-aluminum
propellant flames at pressures between 1 and 40 bar. The results presented here
demonstrate that ULAS in the mid-IR can provide high-fidelity, calibration-free
measurements of gas properties with sub-nanosecond time resolution in harsh,
high-pressure combustion environments representative of rocket motors.

Applied Physics