Halogen Lamps

Halogen lamps were invented in the 1950s. A high-temperature, long-lasting tungsten filament was enclosed in quartz. The quartz enclosure was filled with halogen, producing a bright white light with a bluish tint. Halogen is extremely reactive, and the halogen cycle which leads to the production of this bright light works best in very high temperature. Halogen bulbs are much more efficient and long-lasting than ordinary incandescent bulbs.

There has been evolution in halogen lamps ever since. A small quartz bulb is filled with gas (inert gas like argon or premium gas like krypton or xenon) and of halogen. Since the gas is filled at very high pressure (to make it work efficiently) and operated at very high temperature, the envelop holding the chemically reactive gas should be both heat resistant and of high strength. Hence, quartz was the natural choice over glass. The atoms of the tungsten filament evaporate during the operation of the bulb. The particles condense and settle on the inner surface of the bulb.

Halogen, being a highly reactive gas, reacts with the condensed particles, converting them into tungsten halide. Tungsten halide evaporates easily, and when particles reach the heated filament (due to running electricity) they break to release the halides, and the tungsten particles settle back on the filament. Due to this process, the evaporated particles of the filament are returned and the process of thinning of filament is slowed down. Thus the bulbs are long-lasting in comparison to incandescent lamps. Due to this halogen cycle, the inner surface of the bulb is always clean, leading to bright light even in aging halogen lamps.

However, the halogen cycle is not a fool-proof solution, so even halogen bulbs do not last forever. The tungsten halides that return to the filament may not settle down in the spots from where evaporation had occurred. Thus, the problem of thinning filaments still exists to some extent. Apart from this, the life of a halogen bulb may be lowered due to notching or necking.

Halogen bulbs contain highly dangerous and reactive gaseous material, and so bursting halogen bulbs can be very dangerous. Halogen bulbs should not be touched with bare hand or tampered with in any way, and proper guidelines for installation and handling should be followed.