Electric Light Source Industry

Metal Halide Lamp

Metal halide lamp is the third-generation light source developed on the basis of high-pressure mercury lamp in the 1960s. It is mainly used in lighting, photoengraving, photochemical reaction, coating, ink curing, medical treatment, health care, fluorescence analysis, livestock medical care and sterilization, etc.

Metal halide lamp is filled with metal halide instead of metal. Under the same temperature, vapor pressure of the metal is much lower than that of the metal's halide; moreover, some metals react chemically with quartz bulb, but their iodide will not react with quartz.

Water and oxygen have the greatest effect on the performance of the metal halide lamp, because they are most destructive in the lamp, which is the main cause of the lamp's short life. Purification, split charging and filling methods, etc. of metal halide lamp are all for eliminating its water and oxygen. In the lamp's tungsten-halogen cycle, tungsten on the hot electrode is evaporated into the discharge space and reacts with the vapor and generates tungsten trioxide and hydrogen. The tungsten trioxides deposit onto the low-temperature bulb, and the hydrogen molecules decompose into hydrogen atoms at high temperature. The hydrogen atoms are very active, and will immediately react with the tungsten trioxides deposited on the bulb, and thus free out metal tungsten and water. Then, the generated water returns to the discharge space and chemically combine with tungsten. In this way, water becomes a carrier and transports the tungsten on electrode onto the bulb, which darkens the bulb and speeds up the end of the lamp life.

Functions and effects of quartz glass on metal halide lamp: metal halide lamp is a kind of lamp with great tube wall loading. Temperature of the bulb is generally between 500~1100℃, which is very high. Only quartz glass tube can endure such temperature. Meanwhile, expansion coefficient of quartz glass tube is small, and it will not break for uneven temperature distribution of the light tube. Detrimental impurities in quartz glass tube are hydroxyl, aluminum, calcium, magnesium, lithium, sodium, potassium, ferrum, cobalt and boron, etc. Among these impurities, the most harmful are hydroxyl, potassium, sodium, calcium and ferrum, etc. Because when the hydroxyl seeps into the lamp, it will be resolved into water, hydrogen and oxygen under the high-temperature effect of electric arc, and thus strengthen the water circulation process inside the lamp, and darkens the lamp and ends its life in advance. What's more, the hydrogen in hydroxyl may also react with halogen to generate hydrogenhalide which will capture large amount of electron inside the lamp, making it difficult to turn on the lamp, and thus shortens its life. Quartz glass tube is a transparent amorphous body. When there are masses of impurities like potassium and sodium, the quartz glass tube is easily devitrified at high temperature. As a result, the light emitted by the lamp will be absorbed by quartz devitrification, and the lamp is more likely to break down.

Functions and effects of quartz glass on metal halide lamp: metal halide lamp is a kind of lamp with great tube wall loading. Temperature of the bulb is generally between 500~1100℃, which is very high. Only quartz glass tube can endure such temperature. Meanwhile, expansion coefficient of quartz glass tube is small, and it will not break for uneven temperature distribution of the light tube. Detrimental impurities in quartz glass tube are hydroxyl, aluminum, calcium, magnesium, lithium, sodium, potassium, ferrum, cobalt and boron, etc. Among these impurities, the most harmful are hydroxyl, potassium, sodium, calcium and ferrum, etc. Because when the hydroxyl seeps into the lamp, it will be resolved into water, hydrogen and oxygen under the high-temperature effect of electric arc, and thus strengthen the water circulation process inside the lamp, and darkens the lamp and ends its life in advance. What's more, the hydrogen in hydroxyl may also react with halogen to generate hydrogenhalide which will capture large amount of electron inside the lamp, making it difficult to turn on the lamp, and thus shortens its life. Quartz glass tube is a transparent amorphous body. When there are masses of impurities like potassium and sodium, the quartz glass tube is easily devitrified at high temperature. As a result, the light emitted by the lamp will be absorbed by quartz devitrification, and the lamp is more likely to break down.

Xenon Lamp

Xenon lamp is divided into long-arc xenon lamp and short-arc xenon lamp. The long-arc xenon lamp has both natural cooling type and water cooling type. Wall temperature of the long-arc xenon lamp is between 500~750℃, which is very high. So it has to use quartz tube as its bulb. Xenon lamp is often used in photochemical reaction of long-wave ultraviolet rays, such as photoengraving, copier, plastic and rubber aging test, color fading test/ sterilization of textiles and health care, etc.