QEPAS spectrophones: design, optimization, and performance
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The impact of design parameters of a spectrophone for quartz-enhanced photoacoustic spectroscopy on its performance was investigated. The microresonator of spectrophone is optimized based on an experimental study. The results show that a 4.4 mm-long tube with 0.6 mm inner diameter yields the highest signal-to-noise ratio, which is ∼30 times higher than that of a bare QTF at gas pressures between 400 and 800 Torr. The optimized configuration demonstrates a normalized noise-equivalent absorption coefficient (1σ) of 3.3×10−9 cm−1W/Hz1/2 for C2H2 detection at atmospheric pressure. The effect of the changing carrier gas composition is studied. A side-by-side sensitivity comparison between QEPAS and conventional photoacoustic spectroscopy technique is reported.
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