What Gas Is in Tungsten Iodine Lamp?

There are tungsten vapor, iodine vapor, tungsten iodide gas and inert gas in the iodine tungsten lamp.

Tungsten Vapor

Iodine tungsten lamp is made of tungsten filaments. As a thermal radiation source, high temperatures are generated during the conversion of electrical energy into light energy. At the same time, tungsten diffuses and volatilizes to form tungsten vapor. If there is no corresponding protection, the tungsten atoms will evaporate and the tungsten wire will become thinner, which is why the lamp wall of the incandescent lamp turns black after a long time of use.

Iodine vapor

Iodine vapor is an important gas that can generate tungsten-halogen cycle in tungsten-iodine lamps. The iodine molecules initially added to the bulb decompose into iodine atoms condensed on the shell wall due to heat near the filament, and use it to redeposit the volatilized tungsten on the filament to prevent the glass bulb from blackening and increase the life of the bulb.

Tungsten iodide gas

Tungsten iodide gas is an "intermediate product" of the tungsten iodide cycle. Under appropriate conditions, the above-mentioned iodine atoms react with the tungsten adsorbed on the shell wall to form tungsten iodide gas that easily diffuses to the filament. The temperature at the filament is extremely high, tungsten iodide decomposes again, and tungsten redeposits on the filament. The existence of tungsten iodide helps iodine vapor and tungsten vapor to complete the cycle, making it volatilize, condense and diffuse repeatedly between the shell wall and the filament, further prolonging the service life of the filament.

Inert gas

The inert gas plays the role of "buffer" in the iodine tungsten lamp. Its main function is to make the tungsten form gas convection in the lamp, so as to reduce the precipitation of tungsten and inhibit the evaporation speed of tungsten. The commonly used iodine-tungsten circulation agent is argon gas. The reason why argon is chosen is that its heat transfer coefficient is small, so that the luminous efficiency will not decrease due to cooling of the filament, and it is not easy to conduct electricity, so as to avoid arcing.

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