Abstract
A detailed investigation of the influence of quartz tuning forks (QTFs) resonance properties on the performance of quartz-enhanced photoacoustic spectroscopy (QEPAS) exploiting QTFs as acousto-electric transducers is reported. The performance of two commercial QTFs with the same resonance frequency (32.7 KHz) but different geometries and two custom QTFs with lower resonance frequencies (2.9 KHz and 7.2 KHz) were compared and discussed. The results demonstrated that the fundamental resonance frequency as well as the quality factor and the electrical resistance were strongly inter-dependent on the QTF prongs geometry. Even if the resonance frequency was reduced, the quality factor must be kept as high as possible and the electrical resistance as low as possible in order to guarantee high QEPAS performance.
Highlights
Photoacoustic spectroscopy (PAS) is a powerful technique for trace gas analysis and has been widely used in various fields of physics, chemistry, and biology [1,2,3]
A well-established variant of PAS is quartz enhanced photoacoustic spectroscopy (QEPAS), which was firstly demonstrated by Kosterev et al [4,5] in 2002
Following reasons: (i) the acoustic pressure wave generated by the interaction of the laser beam with the traceOptimization gas was modeled a wave that propagates in free-space, its wavefront was assumed to not Position be distorted by the interaction with the quartz tuning forks (QTFs); (ii) the QTF was modeled as a system of two non-coupled
Summary
Photoacoustic spectroscopy (PAS) is a powerful technique for trace gas analysis and has been widely used in various fields of physics, chemistry, and biology [1,2,3]. For the detection of pure CO2 , the performance of conventional PAS is betters This is because the commercially available QTFs are designed and optimized for timing application with the resonance frequency of 215 (32768) Hz and the slow de-excitation processes of some molecules cannot efficiently follow such a fast laser modulation frequency [12,13]. The light blocked by prongs can result in undesirable background noise which can limit the ultimate detection sensitivity of the sensor [14] To overcome these limitations, custom QTFs with low-resonance frequencies of a few kHz and prong spacings >700 μm have been proposed for QEPAS [8,14,15,16,17]. A detailed analysis of the dependence of the QEPAS sensor performance on the QTF resonance properties have been discussed
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