Near-Infrared Dual-Gas Sensor System for Methane and Ethane Detection Using a Compact Multipass Cell

Yu Zhang,Chuantao Zheng,Weilin Ye,Chunguang Li,Frank K Tittel,Haipeng Zhang,Fang Song,Yiding Wang,Zhenhai Xi,Kaiyuan Zheng

doi:10.3389/fphy.2022.843171

Abstract

In this invited paper, a compact dense-pattern multipass cell-based near-infrared sensor system was demonstrated for detection of parts-per-billion in volume (ppbv)-level methane (CH4) and ethane (C2H6). The dimension size of the fabricated gas cell is 18.5 × 8 × 9 cm3 with an absorption path length of 9.39 m. CH4 measurement was realized within a spectral range of 6,046–6,048 cm−1 and an absorption line of 6,046.95 cm−1. The spectral range for C2H6 detection is 5,951–5,953 cm−1 with an absorption line of 5,951.73 cm−1. Allan deviation analysis was used for evaluating the dual-gas sensing performance, and a detection limit of 78 ppbv for CH4 and 190 ppbv for C2H6 were achieved, respectively, with an averaging time of 0.8 s. Furthermore, CH4 measurement in the indoor and outdoor atmosphere was both performed to verify the field sensing capability of the sensor system. Compared with two separate sensor systems for CH4/C2H6 sensing, the proposed dual-gas sensor system using two near-infrared lasers and one multipass cell has the advantages of low-cost, compact-size without decreasing the selectivity and sensitivity.

Highlights

A dense-pattern multipass cell (MPC)-based near-infrared sensor system was demonstrated for CH4/C2H6 dual-gas detection
Two laser beams were injected into the MPC with an effective path length of 9.39 m
Both indoor and outdoor CH4 concentration levels were measured to verify the performance of the sensor system

Summary

INTRODUCTION

Methane (CH4) and ethane (C2H6) are the two most abundant alkanes in the atmosphere [1–3]. To determine the actual effective optical path length, a sawtooth scan signal with a frequency of 50 Hz was used to change the current of the DFB laser and a CH4 sample with a concentration level of 20 ppmv was injected into the compact. According to the simulation results of HITRAN, under the condition of temperature of 300 K, pressure of 760 Torr and optical path length of 1m, the C2H6 absorption line with one ppmv concentration was obtained. The response characteristics of the dual-gas sensor system for C2H6 detection was determined by measuring the response time by switching the C2H6 concentration level between 0 ppmv and 100 ppmv.

CONCLUSION

DATA AVAILABILITY STATEMENT