Abstract

This paper presents the method and performance of the photoacoustic resonant cell remodified from a Helmholtz cavity that can be used to improve excitation of acoustical signal of the photoacoustic cell by photoacoustic effect. The other advantages of this method are that it can be used to detect flowing trace gases and it has small volume. In our experiments, the conventional nonresonant cell, the original Helmholtz resonant cell, and the remodified Helmholtz resonant cell were designed and tested respectively, based on the measurement of the ${\mathrm{CO}}_2$ contribution of the photoacoustic signal. The nonresonance test of the trace gas analyte ${\mathrm{CO}}_2$ conducted at $125\mathrm{Hz}$ demonstrated signal about $4\mathrm{mV}$ for ${\mathrm{CO}}_2$ concentrations at $300\mathrm{ppm}$ and signal-to-noise (S/N) value ($\sim 32:1$). The original Helmholtz resonant test of the same analyte gas conducted at its resonant frequency demonstrated signal about $43\mathrm{mV}$ and S/N value ($\sim 340:1$). The remodified Helmholtz resonant test of the same analyte gas conducted at its resonant frequency demonstrated large signal about $67\mathrm{mV}$ and high S/N value ($\sim 536:1$). The test results show that the remodified Helmholtz photoacoustic resonant cell has a more outstanding measuring performance and more sensitivity compared to the two others.

© 2011 Optical Society of America

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