The working principle of the diffused barium tungsten cathode is mainly based on thermionic emission and the active effect of barium. The following is its detailed working principle:
Thermionic emission
The diffused barium tungsten cathode first heats the tungsten matrix to a certain temperature (such as around 1400K) to achieve a sufficient level of thermal electron emission. When the tungsten matrix is heated, the electrons inside it will gain enough energy to overcome the surface constraints and escape to become free electrons.
Active effect of barium
During the operation of the cathode, the active substances filled inside (mainly barium salts, such as BaO) will react with the tungsten matrix. These reactions will generate active barium atoms, which gradually diffuse to the cathode surface.
Surface barium layer
On the cathode surface, the diffused barium atoms will form a thin film, usually a thin film diffusion system of tungsten-barium (W-Ba) or tungsten-oxygen-barium (W-O-Ba). This thin film reduces the work function of the cathode surface, thereby further increasing the number of thermal electrons emitted.
Electron emission
Due to the reduction of the surface work function, the cathode can emit more electrons when heated. These electrons can be accelerated by an external electric field and used in various vacuum electronic devices.
In general, the diffused barium tungsten cathode reduces the work function of the cathode surface through heating and the activation of barium, thereby achieving efficient and stable thermal electron emission. This cathode has a wide range of applications in microwave vacuum electronic devices, high-power electron beam equipment and displays.
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