Photoacoustic spectroscopy for detection of trace C2H2 using ellipsoidal photoacoustic cell

Abstract

In this paper, a new type of ellipsoid photoacoustic cell was designed to enhance the photoacoustic effect for the first time. The COMSOL Multiphysics software was used to stimulate the acoustic characteristics of the traditional cylindrical photoacoustic (PA) cell and the ellipsoid PA cell. The resonance frequency, acoustic pressure distribution and acoustic pressure level size in the resonant cavity of the novel PA cell and traditional cylindrical PA cell were analyzed. The novel PA cell was used to detect the concentration of acetylene. In the experiment, the 1532.83 nm absorption spectral line was selected as the measurement spectral line, and the tunable Distributed Feedback (DFB) semiconductor laser was finally selected as the light source. Fabry–Perot (F-P) fiber optic acoustic sensor which has been reported in other paper was used to collect the sound pressure signal. The signal-to-noise (SNR) of the cylindrical photoacoustic spectral system for the detection of acetylene gas was 23 dB, and the detection limit sensitivity was 2.17 ppb. The SNR of the ellipsoid photoacoustic spectral system for the detection of acetylene gas was 34 dB, and the detection limit sensitivity was 1.47 ppb. The performance of the ellipsoidal photoacoustic cell is better than that of the cylindrical photoacoustic cell. The results shown that the novel PA cell can improve the PA effect significantly.