Abstract：The present paper studied the impact of geometry dimensions, located angle and detection position of a quartz tuning fork (QTF) on the sensitivity of QEPAS system. Ten kinds of QTFs were employed to compare the sensitivity with each other, and the results show that the QTF with a wedge-shape top obtains a higher quality factor and turns to be 50% more sensitive than the ones with a regular cuboid top when detecting the water concentration at 7 306 cm-1. By studying the located angle of a QTF, it was found that it nearly makes no difference, but more noise is introduced when there is an angle φ between the laser beam and QTF. The optimal detection position of a QTF appears to be 3.1 cm away from the bottom of the QTF under the case of the normal incidence. At last the influence of external contamination on the resonant frequency of a QTF is discussed. The authors found that the frequency of the QTF decreases along with the contamination increasing. A novel method to lower the frequency of the QTF is proposed. This may make a contribution to the QEPAS used in detecting trace gas with a low V-T relaxation.
Key words：Spectroscopy;Quartz-enhanced photoacoustic spectroscopy;Quartz tuning fork;Optical gas sensors;Sensor optimizing
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