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Conducive to improve transconductance
- Jan 30, 2018 -

1. Tube cathode

Cathode is used to emit electronic components, divided into oxide cathode and tungsten carbide thorium cathode. In general, the oxide cathode is by-product, which uses special filaments to heat the cathode body, such as barium oxide, for hot electron emission. Life expectancy is generally 1000 to 3000 hours. Tungsten carbide thorium cathode is generally direct thermal, by heating can produce hot electron emission, so it is both filament and cathode. In theory, thorium carbide tungsten cathode oxide cathode life is much longer, usually in 2000 ~ 10000 hours or more. High-power launch tube is the most widely used tungsten carbide thorium cathode, oxide cathode generally in the output power of 1kW launch tube in the application.

In recent years, the use of mesh cathode more high-power launch tube. Mesh cathode is made of thinner thorium tungsten wire cylindrical, its advantages are:

1) Since it uses a lot of thorium tungsten wire braided, so the diversion coefficient larger.

2) easy to achieve a smaller gap between the grid, is conducive to improving transconductance.

3) Since the filament is a mesh structure, the current of a single filament is small and the local magnet

Field is weak, so the cathode current generated by the hum is also smaller.

2. Tube gate

The gates of the tubes are divided into a gate, a second gate, sometimes called a control gate, and a screen, depending on the role they play in the tube. The main role of the first gate is to control the cathode current, the role of the second gate is the shield plate pole on the first gate. Gate structure related to its own mechanical strength and heat dissipation, related to the tube can work stably. In order to reduce the transit time of electrons, the interval between the gate and the cathode is very short or even less than 1 mm. Therefore, the manufacturers use gate materials with high mechanical strength, high thermal conductivity, good emissivity and high melting point to avoid Hot touch occurs at very small intervals. A gate and two gate should be strictly on the grid, so that the screen electron capture small, can reduce the curtain consumption, improve the current distribution to improve the sex line.

3. Tube anode

The anode is the electrode that collects most of the electrons emitted by the cathode. When the tube is in operation, due to the bombardment of the surface of the tube by the electron tube and the heat radiation of other electrodes, a large amount of thermal energy is generated at the plate electrode because the power dissipation density of the plate electrode is several tens of watts to several hundred watts per square centimeter. Density using natural radiation or conduction cooling has not qualified. It must be forced to cool. Commonly used in air-cooled, water-cooled and evaporative cooling.