The ceramic metal halide is a variation of the metal-halide lamp which is itself a variation of the old (high-pressure) mercury-vapor lamp. A cmh uses ceramic instead of quartz like a traditional metal halide lamp. Ceramic arc tubes allow higher arc tube temperatures, which some manufacturers claim results in better efficacy, color rendering, and color stability.
The discharge is contained in a ceramic tube, usually made of sintered alumina, similar to what has been used in the high pressure sodium lamp. During operation, the temperature of this ceramic tube can exceed 1200 kelvins. The ceramic tube is filled with mercury, argon and metal-halide salts. Because of the high wall temperature, the metal halide salts are partly vaporized. Inside the hot plasma, these salts are dissociated into metallic atoms and iodine.
