Methane photo-acoustic gas analyzer based on 7.7-μm quantum cascade laser

• Published in: Infrared physics & technology Vol. 117; p. 103858
• Main Authors: Sherstov, I.V., Kolker, D.B., Boyko, A.A., Vasiliev, V.A., Pustovalova, R.V.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-09-2021
• Subjects: Methane; Photo-acoustic gas analyzer; Quantum-cascade laser; Resonant differential photo-acoustic detector; Methane; Resonant differential photo-acoustic detector; Quantum-cascade laser; Photo-acoustic gas analyzer
• ISSN: 1350-4495; 1879-0275
• DOI: 10.1016/j.infrared.2021.103858

•The photo-acoustic methane gas analyzer based on a quantum cascade laser (~7.7 μm), a resonant differential PA detector, and a sealed gas-filled cell was investigated.•The measurement of methane concentration below the background value in the air (~0.3 ppm CH4) is shown.•The standard dispersion was (1σ) ≈ (10–11) ppb CH4.
The photo-acoustic (PA) methane gas analyzer based on a quantum cascade laser (QCL; ~7.7 μm/1800 Hz/24 mW), a resonant differential PA detector, and a sealed gas-filled cell was investigated. The measurement of methane concentration below the background value in the air (~0.3 ppm CH4) is shown, the standard dispersion was (1σ) ≈ (10–11) ppb CH4 with an integration time of 10 s. Under conditions of temperature instability (or emission wavelength) of QCL when normalized to a gas-filled cell, the relative measurement error of the CH4 concentration does not exceed 3%. A decrease in the average QCL radiation power (~24–12–6 mW) leads to a noticeable deterioration in the threshold sensitivity of the PA gas analyzer. It is recommended to increase the average QCL power level to ~50 mW. The dynamic range of measuring the concentration of methane of the PA gas analyzer in the linear mode was ~4 decades (from 0.3 ppm to 2000–3000 ppm CH4).