Characterization of Nanosecond Repetitively Pulsed Discharges by Infra-Red Laser Absorption Spectroscopy

Nanosecond repetitively pulsed discharges (NRPD) have received great attention for their potential in new industrial applications such as plasma-assisted combustion. It has been shown that NRPD can stabilize and improve the efficiency of turbulent lean flames. In this work, we present time-resolved in-situ laser absorption spectroscopy (LAS) measurements in a pin-to-pin reactor containing methane-air mixtures. NRPD (with a frequency in the range 1-30 kHz) are operated in the spark regime. A Quantum Cascade Laser and a tunable Differential Frequency Generator system are used to perform infra-red absorption with a time resolution of a few tens of nanoseconds. The production of nitrogen oxides and the decomposition of methane are monitored during a single pulse. The gas temperature increase is determined by comparing experimental absorption spectra with HITRAN simulations.