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Cooper Hewitt lamp, 1903 Production of high-pressure mercury-vapor lamps, 1965. Charles Wheatstone observed the spectrum of an electric discharge in mercury vapor in 1835, and noted the ultraviolet lines in that spectrum. In 1860, John Thomas Way used arc lamps operated in a mixture of air and mercury vapor at atmospheric pressure for lighting. [4]
Ultra-high-performance lamp. An ultra-high-performance lamp, often known by the Philips trademark UHP, is a high-pressure mercury arc lamp. [1] These were originally known as ultra-high-pressure lamps, [2] [3] because the internal pressure can rise to as much as 200 atmospheres when the lamp reaches its operating temperature.
High-pressure lamps have a discharge that takes place in gas under slightly less to greater than atmospheric pressure. For example, a high pressure sodium lamp has an arc tube under 100 to 200 torr pressure, about 14% to 28% of atmospheric pressure; some automotive HID headlamps have up to 50 bar or fifty times atmospheric pressure. Metal ...
Diagram of a high-pressure sodium lamp A high-pressure sodium lamp, Philips Master SDW-T 100W. Various types of chemistry are used in the arc tubes of HID lamps, depending on the desired characteristics of light intensity, correlated color temperature, color rendering index (CRI), energy efficiency, and lifespan. Varieties of HID lamp include:
A high-pressure sodium street light in Toronto A high-pressure sodium-vapor lamp An HPS lamp that isn't entirely off. A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm. Two varieties of such lamps exist: low pressure and high pressure.
In low-pressure mercury lamps, there is an optimum mercury pressure for the highest efficiency. Photons emitted by ionized mercury atoms can be absorbed by nearby nonionized atoms and either reradiated or the atom is deexcited nonradiatively, too high mercury pressure therefore causes losses of light.