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Abstract
A mass spectrometer was used to analyze the gases in the outer jacket of operating HPS lamps. For new lamps, methane is the major gas, and argon is a minor constituent. As the lamp ages, helium accumulates in the outer jacket and the methane pressure decreases. The voltage, wattage, luminous output, and sodium D line width were monitored as gases were added to the outer jacket of operating HPS lamps. The effect on lamp performance is dependent on the pressure and the nature of the gases added to the outer jacket. Of the three gases (methane, helium, and argon), methane produces the greatest effect on lamp performance and argon the least.