tungsten halogen lamp
Tungsten halogen lamps contain a halogen gas in the bulb, which reduces the filament evaporation rate and thus increases the lamp life. They also have an inner coating that reflects heat. Together, the filling and coating recycle heat to keep the filament hot with less electricity.
These lamps have a very high color rendition index. They also are considerably more expensive to buy than standard incandescent lamps, but are less expensive to operate because of their higher efficacy.
The high operating temperature and need for special fixtures limits the use of tungsten halogens to commercial applications and for use in projector lamps and spotlights.