High-precision detection of acetylene using photoacoustic spectroscopy with a three-step cylindrical cell

High-precision photoacoustic spectroscopy (PAS) with a three-step cylindrical photoacoustic cell (TSC-PAC) was developed for acetylene (C2H2) detection. Finite element analysis was used to investigate the acoustic properties of the proposed TSC-PAC and conventional H-type cylindrical photoacoustic cell (HTC-PAC). Simulation results showed that acoustic pressure signal of the TSC-PAC was higher than that of HTC-PAC with the same dimension. Resonance frequency of the TSC-PAC was identified at 984 Hz. In experimental studies, a plane mirror was used to reflect the incident light and increase the optical length in the PAC. A silicon-cantilever-based fiber-optic sensor was positioned at the terminal point of the TSC-PAC, where the maximum photoacoustic (PA) signal was located. With C2H2 concentration of 100 ppm, the 2f signal of TSC-PAC was 1.43 times that of HTC-PAC. When the integration time was 100 s, the linear fitting (R2) and minimum detection limit (MDL) of C2H2 measured by TSC-PAC at the atmospheric pressure were 0.996 and 13.74 ppb, respectively. The normalized noise equivalent absorption (NNEA) coefficient was 8.18×10-8cm-1·W·Hz-1/2. Both simulation and experimental results proved that the developed TSC-PAC enhanced the performance of the PAS and it had certain application potential in the PAS.