What Is a Cold Cathode?

A cathode in an electron tube that emits electrons without heating. Electron emission is generally used to supply electrons, field emission or secondary emission. The cathodes of photocells, voltage regulator tubes, neon tubes, etc. are all cold cathodes. It is customary to refer to the field emission cathode as a cold cathode. Cold cathode light source is a kind of high-end cold cathode low-pressure glow, based on the production process of neon lamps, which further improves the overall specifications related to the production of light sources such as counter electrodes, powder tubes, manufacturing processes, sophisticated and supporting power supplies Discharge light source.

A cathode that obtains electron emission without heating is called a cold cathode. There are three main types of cold cathodes that have been widely used in the electronics industry:

1. Photocathode that uses light as energy source to cause electron emission, used in photomultiplier tubes and other devices.

2. Secondary emitters that cause solid electron emission by bombarding solids with electrons are used in devices such as orthogonal field amplifiers and electron multipliers.

3. Field emission cathodes and tunnel cathodes that use strong electric fields as energy sources to cause solid electron emission.

In addition, the cold cathode also has negative electron affinity emitters that are currently being developed. Because cold cathodes do not need to be heated, the power supply for heating is omitted, the size of devices and equipment can be reduced, and many other factors that are not conducive to device operation and life due to heat are excluded. Therefore, this type of cathode has great development. future.

Compared with conventional light sources such as incandescent lamps and T5 tubes, cold cathodes can save energy consumption at the same brightness, and can be dimmed according to needs to achieve the brightness required by the place. Not only are the colors colorful, but the average life is up to 30,000 hours, and the cost performance is much higher than conventional light sources. Same brightness,

Electrode: Use high power porcelain ring electrode. Electrode cup is imported

1. Structure and principle

The cold cathode lamp's full name is cold cathode fluorescent lamp, which is a low-pressure glow gas discharge lamp. The temperature of the electrodes at both ends is relatively low, referred to as cold cathode lamp. The cold cathode lamp has the same light emitting mechanism as the neon lamp. The cold cathode lamp is a high-quality neon lamp.

The tube of the cold cathode lamp contains a proper amount of mercury and inert gas, the inner wall of the tube is coated with fluorescent powder, and there is an electrode at each end. When a high voltage is applied to the two ends of the lamp, the electrodes start to discharge without heating. Mercury will be activated by the collision of electrons or atoms filled with inert gas, etc., and excite and emit 253.7nm ultraviolet light. The phosphor on the inner wall of the tube produces visible light. Depending on the composition of the fluorescent material, different colors of light can be emitted. The structure of the cold cathode lamp is shown below: ^[2]

A hot cathode is a 'cathode' that emits electrons due to heating in an electron tube. Can be divided into pure metal (such as tungsten) cathode, thorium tungsten cathode, oxide cathode, barium tungsten cathode, reserve cathode, crushed cathode and so on. Pure metal cathodes and thorium tungsten cathodes have high operating temperatures, and although they have low emission efficiency, they are resistant to ion bombardment, so they are suitable for large and medium power electronic tubes. The oxide cathode has high emission efficiency and low operating temperature, and is generally suitable for low-power electron tubes. When the electron tube is operated in a pulsed state, the oxide cathode can supply a much larger emission current than in continuous operation, so it is also often used in electron tubes that generate high-power pulses. There are two types of cathode heating methods: direct heating and indirect heating.

Direct-heating cathodes are the filaments of electron tubes, and most of them are made into V-shape, W-shape, and spiral shape. When the filament is heated to a certain temperature due to the passage of current, it emits electrons. Indirectly heated cathodes consist of a nickel sleeve with an oxide coating on its outer surface, and a metal wire (hot wire) installed inside the sleeve and insulated from the sleeve. The metal wire (hot wire) itself does not emit electrons, but only plays the role of heating the cathode. Such cathodes are mostly used in low-power electronic tubes heated by alternating current.