High-pressure sodium vapor lamps

Niobium is used as a substrate for platinum in impressed-current cathodic protection anodes because of its high anodic breakdown potential (100 V in seawater), good mechanical properties, good electrical conductivity, and the formation of an adherent passive oxide film when it is anodized. Other uses for niobium metal are in vacuum tubes, high pressure sodium vapor lamps, and in the manufacture of catalysts. 

Other applications of niobium are in electronic and propulsion devices, in electrodes in catalysis and in vacuum tubes and high-pressure sodium vapor lamps. 

Technical limits of exitance also impose minima for the dimensions of medium-pressure light sources (length of arc, length and diameter of bulb), for example, medium-pressure (doped) mercury arcs, high-pressure sodium vapor lamps, and incandescent lamps. 

High-pressure sodium-vapor lamps, IR windows, lighting tubes and lamps, laser materials, light memory, video display and storage, light modulation and shutters. 

High-pressure sodium vapor lamp Lighting tube, special-purpose lamp, infrared transmission window materials Laser materials... 

Purity > 99.7% AI2O3 available at high densities and dependent on the dopant can be translucent with zero porosity. Such material has grain sizes of 3-30 fim and is used as machine tool tips, crucibles, and high pressure sodium vapor lamp tubes. In these purest grades the small amount of impurity is MgO or Y2O3. 

High-pressure sodium vapor lamps are used in street lighting. The two brightest lines in the sodium spectrum are at 589.00 and 589.59 run. What is the difference in energy per photon of the radiations corresponding to these two lines ... 

The light intensity per watt for sodium vapor lamps far exceeds that of fluorescent lamps, high-pressure mercury vapor lamps, tungsten halogen lamps, and incandescent bulbs. 

Because of quite poor color rendition and difficulty in safe disposal of expended lamps, low pressure sodium fixtures are less desirable than high pressure sodium fixtures and are seldom recommended for production facilities. High pressure sodium fixtures are particularly attractive for illuminating large open areas. At locations where power cost is low and where many fixtures are required due to equipment shadowing, mercury vapor fixtures often are preferred because of their lower initial cost, lower replacement lamp cost, and better color rendition. 

High-pressure sodium lamps (sodium vapor pressure lO Pa). 

A weU-known example of this process is the addition of MgO to alumina to permit sintering to theoretical density as required for the production of translucent alumina tubing (see Section 24.17). If, in this example, MgO is added in excess of the solubility limit (-210 ppm is used the actual solubility varies with temperature), then spinel is formed, which may in turn react with Na during use to produce a precipitate of p" -alumina. This reaction can cause the failure of sodium-vapor lamps. Since oxides are frequently processed at high temperatures, it is also likely that the vapor pressure can become appreciable for certain additive oxides. 

Sodium is also used as a heat-transfer medium in nuclear reactors. Liquid sodium is especially good for this purpose because it has a low melting point, a high boiling point, and a low vapor pressure. Also, it has better thermal conductivity and a higher specific heat than do most liquid metals. Finally, its low density and low viscosity make it easy to pump. Sodium is also used in sodium vapor lamps, which are very popular for outdoor lighting. Because each lamp uses only a few milligrams of Na, however, the total quantity consumed in this application is rather small. 

Sodium, owing to the high intensity of its monochromatic yellow D line (589 nm), is extensively used as vapor in high-pressure lamps for outdoor lighting (e.g., highways). Moreover, due to its low work function, sodium is also used as photocathode in... 

The Na D emission can be efficiently generated by an electrical discharge through sodium vapor and so such lamps are used for high-power illumination. But some people find the intense yellow color uncomfortable. The solution use a high-pressure lamp so as to shift the emission toward the red, as we discuss below. 

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