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• A long-path QEPTS gas sensor using a high power Q-switched fiber laser was proposed. • Long optical path and high power are beneficial to the QEPTS sensor. • A minimum detection limit (MDL) of 6.1 ppbv at the 48 s integration time was achieved. A long-path quartz tuning fork enhanced photothermal spectroscopy (QEPTS) gas sensor using a Q-switched fiber laser is proposed. A theoretical model is used to describe the process of the long-path QEPTS sensor and the factors that affect its performance. We can conclude that long optical path and high power are beneficial to the QEPTS sensor from the theoretical analysis. And we use our long-path QEPTS sensor for C 2 H 2 detection at the wavelength of 1531.59 nm. With the scanning time of 4 s and the peak pulse power of 127.5 mW, an Allan deviation analysis shows that our sensor has a minimum detection limit (MDL) of 6.1 ppbv at the 48 s integration time and a good linear response (R-square = 0.99796). [ABSTRACT FROM AUTHOR]

• Scanning cycle is optimized in detail for photoacoustic energy accumulation. • Optimum modulation index is verified to be ∼5 by experiments instead of 2.2. • Frequency and efficiency of QTF are evaluated in a long-term (∼8 months) experiment. • Photoacoustic spectrophones are discussed and compared in their optimum geometric dimensions. Efforts were made in this study to evaluate a series of pivotal techniques in standard quartz tuning fork (QTF) based quartz enhanced photoacoustic spectroscopy (QEPAS) systems for engineering applications. In current QEPAS systems, a scanning ramp combined with high frequency sinusoidal signal is used to drive the light source for photoacoustic excitation, the scanning cycle was optimized for the first time in experiments guaranteeing that photoacoustic energy accumulation finished to achieve the largest photoacoustic signal, and the optimum modulation index was verified by experiments to be ∼5 instead of the simulated result 2.2. As an important step for engineering applications, a long-term (∼8 months) experiment was also carried out to evaluate the stability of QTF's property. In addition, several photoacoustic spectrophone configurations were compared in the optimum geometry parameters, dual-tubes on beam was verified in experiments to be the most efficient one compared with half on-beam and off-beam structures in standard QTF based systems, which is consist with the summary of published papers. [ABSTRACT FROM AUTHOR]