An X-ray technique developed by physicists at the National Institute of Standards and Technology (NIST) is helping to improve the design and energy efficiency of the bright white lights often used to illuminate stadiums, roads and many other settings.
Scientists perform a series of calculations to transform X-ray intensity data (left, a montage of five separate images) into an image of the spatial distribution of mercury atoms in a high-intensity discharge lamp (right). Blue indicates the lowest density of atoms, red the highest.
High-intensity gas discharge (HID) lamps produce 26 percent of the nations light output, but, as a result of their high energy efficiency, consume only 17 percent of the electricity used for lighting. Continuing improvements in energy efficiency and other features will reduce electricity use and the negative environmental effects of power generation. Improved efficiency could save lots of money: HID lamps consume roughly 4 percent of U.S. electricity, equivalent to about $10 billion annually.
The NIST technique uses X-ray imaging to improve understanding of the complex science underlying the HID lamps design. Such lamps have two electrodes in a ceramic tube that contains small amounts of mercury and metal-halide salts. An electric current between the electrodes heats the lamp, vaporizing the mercury and metal-halide salts and producing a gas of electrically charged particles, or plasma. Metal atoms, excited by collisions with electrons in the plasma, emit light at many different wavelengths, producing a bright, white light.
Laura Ost | EurekAlert!
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