What Is an Electron Gun?
An electron gun is a device that generates, accelerates, and condenses a high-energy-density electron beam. It emits an electron beam with a certain energy, a certain beam current, and a speed and an angle. It is also called an electron beam. Electron gun applications include inelastic electron scattering and fluorescent screen lighting.
- In the electron gun,
- An electron gun consists of an emitter (cathode) that generates electrons and a focused electron beam.
- The structure of the electron gun has many forms. According to the structure of the gun body, it can be divided into axial electron gun (straight self-acceleration electron gun) and ring electron gun (electrostatic field deflection electron gun).
- The electron beam generating system is a device that emits electrons and forms an electron beam, as shown in the figure:
Electron gun diversion coefficient
- Diversion coefficient
- When the anode current is limited by space charge, the anode current (emission current) of the electron gun is related to the voltage between the cathode and the anode. If the relativistic effect is not considered, the relationship between them is a 3/2 power ratio relationship, also known as half Cubic Law.
- Under the space charge limitation, regardless of the shape of the electrode system, the law of cubed two-thirds is generally applicable. The shape of the electrodes is different and only affects the previous scale factor. When the shape of the electrode is constant, in general, the conductance coefficient is a constant and has nothing to do with temperature. The size of the conductance coefficient indicates the ability of the electron gun to emit electrons. In other words, the conductance coefficient is a measure of the intensity of the electron beam, which characterizes the space charge of the electron beam.
Electron gun emissivity
- Emissivity
Electron gun brightness
- brightness
Electron gun girdle
- Girdle
- In the axisymmetrically convergent electron gun, electrons are emitted from the cathode, and a certain shape of the electron beam is formed under the action of the electrostatic field formed by the electrodes in the gun and the space charge of the electron itself. Girdle, or injection waist.
Electron gun area compression ratio
- Area compression ratio
- It refers to the ratio of the cathode area to the cross-sectional area of the injection waist, and also the ratio of the average current density of the injection waist to the average current density of the cathode emission. The cathode cross-sectional area is generally used instead of the cathode sphere area.
- The magnitude of the compression ratio depends mainly on the cathode emission current density.
Electron gun range
- Range
- The distance from the anode of the electron gun to the injection waist formed by the electron gun. Generally speaking, people hope that the range is large enough so that the electron beam can enter the high-frequency field region under the optimal injection conditions.
Electron gun laminarity
- The so-called laminarity of the electron beam is only a qualitative concept. Generally, whether the trajectory of the electron beam crosses or not is used to judge the laminarity. The electron beam with good laminar flow can obtain a good flow rate with a lower magnetic field during magnetic focusing, and the defocus of the electron beam caused by the high frequency field is also small. Conversely, an electron beam with poor laminar flow will make its flow rate poor and its defocusing increased. Laminarity is an important judging property to measure the quality of the electron beam.