Why halogen gas ?

• long life time
• minimized filament evaporation

The infrared halogen lamps filling gas is a compound of neutral gas and halogen:
The filament life time is increased and the lamp efficiency is kept constant.

• halogen regenerates the filament and avoids tube blackening
• neutral gas avoids filament oxidation
• pressurized gas limits filament evaporation

Why quartz tube ?

• withstand high temperatures
• heat shock resistant
• transparent to infrared radiation

Why tungsten filament ?

• fast response time
• very high melting point (3400 degrees C)