A carbon monoxide and thermometry sensor based on mid-IR quantum-cascade laser wavelength-modulation absorption spectroscopy

Abstract

A mid-infrared wavelength modulation spectroscopy (WMS) absorption sensor utilizing a quantum cascade laser (QCL) source for carbon monoxide detection at 4.6 μm and high-temperature thermometry has been developed and demonstrated. Measurements are made in a room-temperature gas cell and in high-temperature reflected-shock-heated gases. Room-temperature results demonstrate a minimum CO detectivity of 0.03 ppm per meter of absorption path length at a 1-kHz detection bandwidth, representing an order-of-magnitude increased sensitivity compared to scanned-wavelength direct absorption. High-temperature shock tube measurements demonstrate sensitive thermometry from 850 to 3500 K for pressures near 1 atm at detection bandwidths of 500 Hz and 1 kHz. Sensor determined temperatures agree with the post-reflected-shock conditions within ±1.9% (1σ deviation). To our knowledge, the thermometry measurements presented here represent the first WMS high-temperature thermometry measurements made using a QCL.