Introduction of xenon lamp with xenon bulb

Long arc xenon lamps are made into tubes. The tube is made of transparent quartz tube with high temperature resistance and small thermal expansion coefficient. Two thorium tungsten (or barium tungsten) electrodes are sealed at both ends. The distance between electrodes is generally greater than 100 mm, and the tube is filled with high-purity xenon. The structure of water-cooled long arc xenon lamp is shown in Figure 5-20.

The arc discharge of long arc xenon lamp needs to be started by high frequency and high voltage pulse breakdown. Under the action of high voltage pulse, the channel of spark discharge is first formed in the lamp tube, and the electrons and ions generated from it continue to ionize neutral gas molecules and atoms under the action of electric field, resulting in avalanche process. Under the impact of ions, the electrode is heated to become a heat emitter, which emits a large number of hot electrons and generates a large current, thus forming a stable arc discharge. Because it is high-pressure gas discharge, the discharge current is usually high-temperature plasma. When in use, it can be directly connected to the mains network without ballast, which can improve the power factor and reduce the circuit loss.

The starting device circuit is shown in Figure 5-2 1. In the figure, T 1 is a step-up transformer, T2 is a pulse transformer, and C2 is a bypass capacitor. After the circuit is connected, the power supply voltage is boosted by the booster transformer and charged to C 1. When the voltage on C 1 reaches a certain value, it discharges through the spark gap g. At this time, the capacitance C 1 and the T2 primary coil form an attenuation oscillation loop, and its frequency value depends on the product of the capacitance of C 1 and the inductance of the T2 primary coil. In this oscillation circuit, the frequency rises to about 100 kHz, and this high-frequency voltage rises to 20 ~ 30 kV through T2. This voltage is applied to both ends of the xenon lamp tube through C2, and xenon is decomposed under the action of high frequency voltage and transited to self-sustaining arc discharge. At this time, the light is on, S 1 is off, and the power supply is directly provided by the mains network. If the T2 secondary conductor can't bear the heavy current, S2 needs to be turned off, and the lamp tube has entered the normal working state. The function of C2 is to prevent high-frequency pulses from being sent to the power grid.

Xenon is an element with larger atomic number (i.e. heavier element) and larger atomic radius in inert gas. In arc discharge, the energy lost by elastic collision between electrons and gas is inversely proportional to the atomic weight of gas, so compared with other inert gases, xenon arc discharge has less loss and higher luminous efficiency. At the same time, the ionization potential of xenon is low, and the voltage drop near the electrode is small during discharge, which can prolong the life of the electrode. Due to the characteristics of xenon atomic structure, the spectrum emitted by long arc xenon lamp is very close to sunlight, which is the biggest feature of xenon lamp.

The power of fluorescent lamps is limited, usually 5 ~ 100 watt. The power of xenon lamps can range from 1 10,000 watts to hundreds of thousands of watts. The working temperature of xenon lamp is very high, so natural cooling alone is not enough. It needs forced cooling, or air cooling or water cooling. The luminous efficiency of neon lamp is relatively high, about 24 ~ 37 streams/watt, and that of water-cooled xenon lamp can reach 60 streams/watt, with a general service life of 3000 hours. The light emitted by a 50,000-watt xenon lamp is equivalent to 1000-watt fluorescent lamp 1000 or 90 400-watt high-pressure mercury lamps. It is suitable for large-area lighting in squares, parks, stadiums, large construction sites, open-pit coal mines, airports and other places, and can also be used as a light source for film photography, color photography, plate making and copying. Because the light it emits is close to sunlight, it can be used as artificial aging light source and simulated sunlight for color inspection of cloth fabrics, aging test of drugs and plastics, plant cultivation, photochemistry and so on.