What is a tungsten halogen lamp and what is its principle?

Lamps filled with halogen circulating agent are called tungsten halogen lamps. The function of the halogen recycling agent is to form volatile compounds from the evaporated tungsten, and these compounds decompose near the bulb, allowing the tungsten to return to the filament. The principle is that under appropriate temperature conditions, the tungsten evaporated from the filament reacts with halogen in the bubble wall area to form volatile tungsten halogen compounds. When the halogen tungsten compound diffuses to the area around the hotter filament, it decomposes into halogen and tungsten. The released tungsten part returns to the filament, and the halogen continues to diffuse to the lower temperature area to combine with tungsten, so the life of the filament is extended. The extension also avoids the blackening phenomenon caused by the deposition of tungsten on the bubble wall.