The working principle of a magnetron is a complex and intricate process, mainly based on the motion laws of electrons in an electromagnetic field.

Basic structure and composition:



Magnetron is mainly composed of cathode, anode, magnetic field system, and cavity. The cathode is the source of electron emission. By heating the cathode, the electrons on its surface gain sufficient energy to cross the potential barrier on the cathode surface and enter the pore area of the anode. The anode is a metal cavity with holes, and electrons accelerate under the action of the anode electric field. A magnetic field system is a magnetic field generated by permanent magnets or electromagnets, which provides a stable magnetic field environment for the movement of electron beams.

Working principle:


The working principle of magnetron can be divided into three processes: electron emission, electron beam, and electromagnetic wave generation.
(1) Electron emission: The cathode heats up the electrons on its surface to obtain sufficient energy, thereby crossing the potential barrier on the cathode surface and entering the pore area of the anode. These emitted electrons are called electron clouds.
(2) Electron beam: The magnetic field system generates a strong magnetic field, causing the electron cloud to deflect when entering the anode hole, forming an electron beam. The electron beam moves in a spiral shape under the action of a magnetic field, while advancing along the direction of the anode hole.
(3) Electromagnetic wave generation: When an electron beam passes through an anode hole, a changing current is generated due to changes in the velocity and acceleration of electrons in the magnetic field. This changing current forms high-frequency oscillations on the anode, resulting in the generation of microwave electromagnetic waves. Specifically, when an electron beam interacts with a high-frequency electromagnetic field, the electron will obtain energy from a constant electric field and convert it into microwave energy. This energy conversion process continues inside the magnetron, maintaining high-frequency oscillation and generating stable microwave output.

The working mode of magnetron:
Magnetron typically operates in a π - mode state. In this state, the phase difference of the microwave electric field between the adjacent resonant cavity openings is exactly 180 °, indicating that the direction of the microwave electric field is exactly opposite. Although this microwave field is a standing wave field, in the case of π mode, it is equivalent to two identical microwave fields moving in opposite directions on the circumference, and the phase velocities of the two fields are equal. The electrons emitted from the cathode undergo cycloidal motion under the action of an orthogonal electromagnetic field. Adjust the DC voltage and constant magnetic field so that the average drift velocity of electrons in the circumferential direction is equal to the phase velocity of a microwave field moving in its direction. In this way, electrons can move synchronously with the microwave field.

During synchronous motion, electrons in the microwave deceleration field gradually transfer their DC potential energy to the microwave field and approach the anode, finally being collected by the anode. These electrons transfer energy to the microwave field, which is beneficial for establishing stable microwave oscillations in the magnetron. The electrons in the microwave acceleration field obtain energy from the microwave field and move towards the cathode, finally hitting the cathode. These electrons are called disadvantageous electrons, and when they bombard the cathode, they produce a large number of secondary electrons, increasing the number of interacting space electrons.

The working principle of a magnetron is based on the motion law of electrons in an electromagnetic field, which generates high-frequency electromagnetic waves through the interaction between electrons and the electromagnetic field. This working principle makes magnetrons widely applicable in fields such as radar and microwave heating.