Investigation of gas composition on discharge lamps fractured during operation by means of mass spectrometry
| Autor: | Péter Kovács, György Hárs, Agoston Boroczki |
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| Rok vydání: | 2005 |
| Předmět: | |
| Zdroj: | Measurement Science and Technology. 17:79-83 |
| ISSN: | 1361-6501 0957-0233 |
| Popis: | Recently, metal-halide lamps were also used as automotive light sources because of their major advantages over tungsten halogen lamps (longer lifetime, improved efficacy). However, the lifetime of the lamps is strongly deteriorated by impurities present in the lamp. The impurities can be investigated by a destructive test method when the discharge vessel is fractured in high vacuum conditions, and the resultant residual gas is subject to analysis. Impurity tests have been carried out on inoperative lamps at room temperature so far. However, both the filling components and some of impurities of the lamp are in gaseous phase close to the steady-state lamp operating temperature only. At room temperature most of the dose constituents, including some of the impurities, are in condensed phase, i.e. solid or liquid. Thus they hardly show up in the mass spectrum. Consequently, the result of mass spectrometry analysis on the gas composition of an operating lamp can be substantially different from that of an inoperative lamp. In order to perform gas impurity analysis on operating lamps, a mass spectrometer based in situ fracture stage has been built, which operates at an elevated temperature. The term 'elevated temperature' means a temperature value that is significantly higher than room temperature but cannot be defined accurately in degrees because of its rapid change at fracturing. A microphonic noise impulse is used to synchronize the spectrum recording with the fracturing, so that we could analyse the spectrum right after fracturing. This spectrum is the most informative since it is recorded before major condensation happens. Some test results are also presented along with the details on the method of measurement. |
| Databáze: | OpenAIRE |
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