Effect of detector nonlinearity and image persistence on CARS derived temperatures

The image persistence of self-scanning photodiode arrays (IPDA) incorporating P-20 phosphor-based intensifiers is shown to make them unsuitable for single-pulse CARS temperature measurements in turbulent combustion. Correcting CARS flame spectra for the nonlinear response of the IPDA detectors increases CARS-derived temperatures by about 3-6 percent. This error is partially offset by correcting for the perturbations in the N2 vibrational population resulting from stimulated Raman pumping. The effect of these population perturbations on CARS-derived temperatures is determined. CARS flame spectra obtained with uncorrelated pump beams that are corrected for IPDA nonlinearity and stimulated Raman pumping are shown to give temperatures in good agreement with combined thermocouple/sodium line-reversal measurements.