Ppb-level gas detection using on-beam quartz-enhanced photoacoustic spectroscopy based on a 28 kHz tuning fork

Abstract

In this paper, an on-beam quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor based on a custom quartz tuning fork (QTF) acting as a photoacoustic transducer, was realized and tested. The QTF is characterized by a resonance frequency of 28 kHz, ~15% lower than that of a commercially available 32.7 kHz standard QTF. One-dimensional acoustic micro resonator (AmR) was designed and optimized by using stainless-steel capillaries. The 28 kHz QTF and AmRs are assembled in on-beam QEPAS configuration. The AmR geometrical parameters have been optimized in terms of length and internal diameter. The laser beam focus position and the AmR coupling distance were also adjusted to maximize the coupling efficiency. For comparison, QEPAS on-beam configurations based on a standard QTF and on the 28 kHz QTF were compared in terms of H 2 O and CO 2 detection sensitivity. In order to better characterize the performance of the system, H 2 O, C 2 H 2 and CO 2 were detected for a long time and the long-term stability was analyzed by an Allan variance analysis. With the integration time of 1 s, the detection limits for H 2 O, C 2 H 2 and CO 2 are 1.2 ppm, 28.8 ppb and 2.4 ppm, respectively. The detection limits for H 2 O, C 2 H 2 and CO 2 can be further improved to 325 ppb, 10.3 ppb and 318 ppb by increasing the integration time to 521 s, 183 s and 116 s

Ultra-highly sensitive HCl-LITES sensor based on a low-frequency quartz tuning fork and a fiber-coupled multi-pass cell

“…When the MPC was filled with pure N 2 , a 2D beam profile of the output laser beam from FC-MPC at the target wavelength was also measured by employing a pyrocamera and shows a good beam profile quality. After passing through the FC-MPC, the laser beam was collimated by using a fiber collimator (FC) at first and was ultimately focused on the base of the QTF prongs, where the strongest LITES signal is expected [21] . In the system, the focal length of the used lens is 30 mm.…”

“…In 2002, quartz-enhanced photoacoustic spectroscopy (QEPAS) was reported for the first time [18] . A low-cost and wavelength independence quartz tuning fork (QTF) is employed as an acoustic wave transducer to measure the photoacoustic signal produced by target gas [19] , [20] , [21] , [22] , [23] . The tiny size and high-quality factor of QTF make QEPAS system compact and immune to the background noise [24] , [25] , [26] , [27] , [28] .…”

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

“…Therefore, compact nearinfrared laser source can be used for the two gas species detection. Compared with mass spectrometry and gas chromatography, infrared absorption spectroscopy, including photothermal and photoacoustic spectroscopy [11][12][13][14][15][16], provides a less-costly approach for CH 4 and C 2 H 6 concentration detection, and enables real-time measurement without the need for pretreatment or accumulation of target gas samples.…”

Spider Silk-Improved Quartz-Enhanced Conductance Spectroscopy for Medical Mask Humidity Sensing

“…[30][31][32][33][34]. The QTF's remarkable advantages attract the attention of researchers, including its stable oscillation frequency, high quality factor, low power consumption, concise structure, and resistance to surrounding electromagnetic interference [35,36]. QTFs can be used in a wide temperature range from −40 • C to 85 • C and in an ultrahigh humidity environment [37].…”