Abstract
Pulsed cavity ringdown spectroscopy (CRDS) is used to develop a novel, ultra-fast, high-sensitivity diagnostic for measuring species concentrations in shock tube experiments. The diagnostic is demonstrated by monitoring trace concentrations of ethylene in the mid-IR region near 949.47 cm(-1). Each ringdown measurement is completed in less than 1 mu s and the time period between successive pulses is 10 mu s. The high sensitivity diagnostic has a noise-equivalent detection limit of 1.08 x 10(-5) cm(-1) which enables detection of 15 ppm ethylene at fuel pyrolysis conditions (1845 K and 2 bar) and 294 ppb ethylene under ambient conditions (297 K and 1 bar). To our knowledge, this is the first successful application of the cavity ringdown method to the measurement of species time-histories in a shock tube. (C)2015 Optical Society of America