Burst-mode 100 kHz N2 ps-CARS flame thermometry with concurrent nonresonant background referencing.

ABSTRACT

A burst-mode nitrogen (N2) picosecond vibrational coherent anti-Stokes Raman scattering (ps-VCARS) system is presented for accurate flame thermometry at 100 kHz repetition rate. A frequency-tripled ps burst-mode laser is used to pump a custom optical parametric generator/amplifier to produce 607 nm broadband Stokes pulses with 120cm-1 bandwidth, along with a narrowband 532 nm pump/probe beam. A simultaneous shot-to-shot nonresonant background (NRB) measurement is implemented to account for Stokes spectral profile and beam overlap fluctuations. The 100 kHz ps-VCARS data are benchmarked in a near-adiabatic CH4/air Hencken calibration flame with an accuracy of 1.5% and precision of 4.7% up to peak flame temperatures. The use of N2 VCARS and simultaneous NRB measurements enables high-speed thermometry for a wide range of fuels and combustion applications.