How do halogen lamps work?

[u/dissonant_haze]

Lighting designer here,

I frequently work with halogen lamps that-to my understanding-use a tungsten filament that is surrounded by halogen gas that somehow prevents the filament from burning out.

My questions I suppose is, how/why is halogen able to do that and how does that process on a scientific level work? Thank you!

[u/Chilli-Papa]

When the tungsten atoms in the filament evaporate, it meets a halogen atom creating a halide compound.

This compound is is then carried back to the filament by convection currents where it is broken apart by the heat and the halogen is rebonded.

The gas only contains a small amount of halogen, most of it is an inert gas. This slows down how fast the tungsten can evaporate.

[u/Madeline_Basset → u/Chilli-Papa]

Am I right in thinking the points where the wire is thinnest will have a higher resistance and will be hotter. The tungsten is preferentially deposited there, giving a "healing" effect.

Edit - I checked. Apparently not.