The work detailed in the dissertation has resulted in a photoacoustic gas detector chamber that has been proved to be applicable for measuring very low concentration gas traces in ambient air. Calculation tools were developed for photoacoustic cell design, namely (i) a method estimating the acoustic quality factor of a cavity even for open configurations; and (ii) a technique calculating the effectiveness of light-sound energy conversion. An open, windowless resonant photoacoustic chamber was designed, that has high acoustic quality factor and good noise suppression. In such a chamber neither the window material nor the contamination adsorbed on the window surface can contribute to the generation of unwanted coherent background signal. The most important factor limiting the applications of high quality factor resonant photoacoustic cells is the resonant frequency shift due to the possible temperature and gas density variations in the chamber. To compensate this drift, a unique electronic resonance tracking system was constructed. A calibration experiment applying a grating tuned CO₂ laser was performed. The achieved detection limits were 8 ppb for ethylene, 50 ppt for sulphur-hexafluoride, and 11 ppm for carbon-dioxide. The reliability of the system was determined by three repeated measurement campaigns over a month, and it was found outstanding. The photoacoustic detector system was also tested against a conventional analytical technique and good agreement was found with the colorimetric ammonia detection method recommended by the NIOH.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/290608 |
| Date | January 1996 |
| Creators | Angeli, Gyorgy Zsolt, 1954- |
| Contributors | Szilagyi, Mike N. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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