| Autor: |
Hashiguchi, Koji, Amano, Minami, Cygan, Agata, Lisak, Daniel, Ciuryło, Roman, Abe, Hisashi |
| Předmět: |
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| Zdroj: |
AIP Conference Proceedings; 2024, Vol. 3230 Issue 1, p1-9, 9p |
| Abstrakt: |
The high-precision measurement of trace water vapor (trace moisture) in gases is important in technology-intensive industries. We have been developing measuring instruments for trace moisture using cavity ring-down spectroscopy (CRDS). In CRDS, an optical cavity consisting of highly reflective mirrors is used as a sample cell to extend the effective optical path length. We measured the ring-down time in dry N2 gas and acquired the absorption spectra of H2O near 7180 cm–1. When we acquired the absorption spectra in the dry N2 gas, periodic structure which was not related to the water absorption line was observed. This structure was caused by fringe noise, which occurred when the reflected light from an optical component surface incident on the cavity. In our measuring system, to stabilize the resonant frequencies of the cavity, the length of the cavity was adjusted using a piezoelectric actuator (PZT) mounted at one end of the cavity. To accurately measure trace moisture, the sample cell was sealed using windows to prevent moisture from entering the cell from the outside, and the PZT was placed outside the sample cell to avoid the effects of water desorption from the element. To adjust the position of the mirror, the mirror and a window were connected and their position was moved using the PZT. In this structure, because the distance between the mirror and the window was small and they were fixed parallel to each other, it was difficult to prevent the reflected light from returning into the cavity, which tended to cause fringe noise. In this study, to eliminate the fringe noise, the mirror and the window were separated so that they could be adjusted independently. In addition, the window was wedged so that the light reflections on both sides were not collinear. The mirror and the PZT were directly connected and placed inside the cell. The gas flow was designed so that the gas was discharged without stagnation to prevent desorbed moisture from entering the measurement space. This improvement has made it possible to measure the trace moisture more precisely. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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