The Magnetron is a high power microwave oscillator, uses the interaction of electric and magnetic fields in a cavity to produce oscillations of very high power. It was invented by Randall and Boot. The construction of cavity magnetron is shown in the figure.
As shown in the given diagram the magnetron consists of the anode block made of copper or brass. It is in the cylindrical shape through which the even number of cavities of the same size towards the external circumference is made at the center of the anode block. There is a hole in which the cathode is located. The center hole of the anode block is connected with each of the cavity by slot coupling. The output of the magnetron is taken with help of loop coupling. Around the anode block there is a strong permanent magnet across the cathode with opposite ends.
Working of Magnetron
When we switch on the circuit, the cathode starts to emit the electrons of the permanent magnet would not be present, the emitted electrons from cathode would be collected by the anode just like the normal diode action, now due to the presence of strong magnet across the cathode there will be a strong magnetic flux around the cathode the emitted electrons from the cathode will have their magnetic field which will react with the field of permanent magnet. Now the emitted electrons will be forced to move around the cathode until it joint back the cathode element.
As a result a crowed of electrons will be produced around the cathode and a strong electric field will be developed in front of the cavities. This strong field will excite the cavity and oscillation will take place at very high frequency. This high power o/p signal is achieved or taken out by the loop coupling from any cavity for the required operation. The o/ of magnetron is in the range of microwave length of frequencies as well as tis power o/p is very high in terms of kilo watts.
Therefore, it is mostly used in radar system for power transmission. It is commonly used in the microwave ovens. It is also used in industrial heating purposes.