Multi-pass Differential Photoacoustic Sensor for Real-Time Measurement of SF₆Decomposition Component H₂S at the ppb Level

Abstract

We designed and implemented a photoacoustic (PA) sensor for H 2 S detection in SF 6 background gas based on a multi-pass differential photoacoustic cell (MDPC) and a near-infrared distributed feedback (DFB) laser. In the MDPC apparatus, two resonators with identical geometric parameters were vertically and symmetrically embedded. The differential processing algorithm of two phase-reversed signals realized the effective enhancement of the PA signal and suppressed the flow noise in the dynamic sampling process. In addition, the λ/4 buffer chamber in the MDPC was utilized as a muffler to further reduce the flow noise and realize the dynamic detection of H 2 S. The collimated excitation light was reflected 30 times in a multi-pass structure constituted of two gold-plated concave mirrors, and an absorption path length of 4.92 m was achieved. Due to the high gas density of SF 6 , the relationship between the signal-to-noise ratio (SNR) and the gas flow was different between SF 6 and N 2 background gases. The maximum flow rate of the characteristic gas components detected in the SF 6 background is 150 standard cubic centimeters per minute (SCCM), which is lower than 350 SCCM in N 2 . The linearity property was analyzed, and the results show that the sensitivity of the sensor to H 2 S in the SF 6 background was 27.3 μV/ppm. With the structure, parameters, temperature, gas flow, and natural frequency of the MDPC been optimized, a minimum detection limit (MDL) of 11 ppb was reached with an averaging time of 1000 s, which furnished an effective preventive implement for the safe operation of gas insulation equipment.

Ultrahigh Sensitive Trace Gas Sensing System with Dual Fiber-Optic Cantilever Multiplexing-Based Differential Photoacoustic Detection

“…33,34 We combined the DPAC with the multipass technology to construct an H 2 S photoacoustic sensor with a detection limit of 11 ppb. 35 In addition, with the advantage of the differential structure, the maximum flow allowed by the system was 150 sccm on an SF 6 background. However, the scheme of applying dual fiber-optic cantilever differential detection technology to H 2 S detection is still vacant.…”

“…The detection limit of 109 ppb was achieved by combining the DPAC with a high Q-value in the system. For further improving the interaction length between excitation light and target gas to enhance the detection sensitivity. , We combined the DPAC with the multipass technology to construct an H 2 S photoacoustic sensor with a detection limit of 11 ppb . In addition, with the advantage of the differential structure, the maximum flow allowed by the system was 150 sccm on an SF 6 background.…”

High-Precision Photoacoustic Nitrogen Dioxide Gas Analyzer for Fast Dynamic Measurement

“…Therefore, a higher gas flow rate can achieve a better performance of the PAS analyzer. However, gas pump noise and gas flow can extremely affect the detection limit of the system. , In our previous studies, differential resonant PA cells were used to attenuate gas flow noise. , …”

High-Precision Multipass Fiber-Optic Photoacoustic Gas Analyzer Based on 2f/1f Wavelength Modulation Spectroscopy

“…Photoacoustic (PA) spectroscopy (PAS) is one of the key sensitive gas analysis technologies. − Compared with direct absorption spectroscopy, − it has the characteristics of no background, which is beneficial to improve the sensitivity of gas detection. , Among various PAS systems, − the fiber-optic PA sensor uses a fiber interferometers to detect PA signals, which has the advantage of intrinsic safety. − The fiber-optic PA sensor based on the extrinsic Fabry–Perot (F–P) interference (EFPI) has the characteristic of a simple structure andrealizes the high-sensitive detection of the PA signal. − However, when the fiber-optic PA sensor is installed into the traditional resonant PA cell, the volume of the gas chamber is very large. According to the basic principle of PA gas detection, the PA signal is enhanced with a decrease in the volume of the gas chamber.…”