A. Alquaity, E. Essebbar, A. Farooq
Optics Express, Issue 23, 7217-7226, (2015)
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 µs and the time period between successive pulses is 10 µs.
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.