How does Magnetron work?

How-does-Magnetron-work


How does Magnetron work?

Cavity magnets are also used in microwave ovens, where they are responsible for producing high-power microwaves. Cavity magnets work on the principle of LC oscillation. LC oscillation occurs when the charged capacitor is placed with an indicator.

This simple arrangement creates motion behind and in front of the electron. When an antenna with an inductor connected to it is placed near the inductor of the LC circuit, the antenna radiates electromagnetic waves. 

It is clear the theory behind the cavity magnet, the energy oscillation, and related radiation of this theoretical device will go faster, as it loses energy in the form of radiation. How can this theoretical device be made practical?

How-does-Magnetron-work

Consider a cathode and a filament. The current flowing through the filament will heat the cathode and cause electrons to emanate from it. This phenomenon is known as thermionic emission. Interestingly, in this case, the electrons return to the cathode. 

If we place an anode with positive potential, the emitted electrons are accelerated and move towards the anode. As the theory of radioactivity states, charges produce radiation, but in this system, electrons radiate inefficiently because they spend very little time in the interaction space.

To increase the time spent by electrons in this space, a permanent magnet is introduced into the structure. The magnetic field forces the electrons to take a curved path. Since the path of the electrons is now curved, the time spent by the electrons in the interaction space is increased. 

The final structure thus formed is known as the hull magnet. Magnetrons are more efficient than the previously described technology, however, their efficiency can be further improved with the help of LC oscillation, which we saw at the beginning of this report. Let's see how we get a swing in a magnet. 

To achieve oscillation, the anode is designed with holes. These cavities make huge differences in magnetic physics. To understand this, let’s consider a simple case. Consider a metal bar with a cavity. Suppose a negative charge is moving near the metal. The negative charge will obviously remove the electrons near it,

How-does-Magnetron-work

As shown in this animation. Similarly, when the negative charge moves closer to the cavity, the electrons around the cavity surface are disturbed. You can see that this disturbance causes the transmission of positive and negative charges across the surface of the cavity. 

In short, the cavity surfaces act like capacitor plates. If you attach an indicator across the cavity surface, the charges will start to fluctuate. This general physics is the basis of the cavity magnet. A magnetic has many such cavities. 

Many electrons are emitted from the cathode by thermionic emissions Let's track the effect of the first electrons generated in these cavities As described above, this selection will induce positive and negative charges on the cavity surface. Here, the cavities are arranged in a circular manner. 

This means that the charged cavity cannot be in the joint separation of the surface. To keep the electric field zero in the metal, all the cavity pairs have to be charged with the opposite pole. An interesting point to note here is that the curved surface of the cavity acts as an indicator. 

This means that the accumulated charges will go for LC oscillation at the same time. With the help of a metal loop and an antenna, this pendulum is converted into EM waves. Electrons continuously flow from the cathode to the anode and transfer their energy as these pendulums will remain in the magnet.

Now let us see what happens to the remaining electrons in the interaction space. The first electron to reach the surface of the cavity has already formed a charge pattern in the cavities. 

This means the rest of the electrons will be attracted to the positively charged regions and they will form an interesting spoke wheel pattern like this. Since the charges in the cavities oscillate, the spoke wheel must spin as illustrated. This phenomenon may be related to the analogy of a carrot and a stick. 

Here, no matter how many steps it takes to reach the carrot, the carrot is always out of its reach. You must have noticed that the antenna is only connected to one cavity since the lines of the magnetic field generated in one cavity also connect to other cavities. This phenomenon is called reciprocal attachment. 

This means that the emission of magnetic energy from one cavity will be equal to the emission from all the combined cavities.

The cavity magnet was created in the UK during World War II to enhance radar technology. Cavity magnets were able to produce high-powered pulses at a much shorter wavelength and this made it possible to detect small objects. The compact size of the cavity magnetron makes the radar size even smaller.
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