How is bunching achieved in a cavity magnetron?

Spaced around the rim of the chamber are cylindrical cavities. Slots are cut along the length of the cavities that open into the central, common cavity space. As electrons sweep past these slots, they induce a high-frequency radio field in each resonant cavity, which in turn causes the electrons to bunch into groups.

How is bunching achieved in a cavity magnetron explain the phase focussing effect?

Bunching takes place in magnetron like Klystrons which is known as phase focusing effect. This effect is useful for the favored electron to maintain the phase . Since such electron are retarded at each interaction with RF field. Diagram shops the wheel spoke bunches in the cavity magnetron.

What are the modes of magnetron?

There are three types of magnetrons: Negative resistance type. Cyclotron frequency type. Travelling wave or Cavity type.

What is the principle of magnetron?

The magnetron is a high-powered vacuum tube that works as a self-excited microwave oscillator. Crossed electron and magnetic fields are used in the magnetron to produce the high-power output required in radar equipment.

Why magnetron is called cross field device?

The magnetron is called a “crossed-field” device in the industry because both magnetic and electric fields are employed in its operation, and they are produced in perpendicular directions so that they cross. The applied magnetic field is constant and applied along the axis of the circular device illustrated.

What is frequency pulling and pushing in magnetron?

Frequency pulling in magnetrons : Frequency pulling is caused by changes in the load impedance reflected into the cavity resonators. Frequency pushing in magnetrons: Frequency pushing is due to the change in anode voltage which alters the orbital velocity of electron clouds.

Why magnetron is called crossed field device?

What is pi mode in magnetron?

For sustaining the oscillation in a magnetron, the phase difference between two adjacent anode plate should equal (2πn/N) where N is the number of cavities and n is any integer, this gives rise to π mode operation.

What is the frequency of a magnetron?

It is quite evident that magnetron does not generate one frequency but a bandwidth spanning from 2.4 to 2.5 GHz.

What is cross field effect?

Crossfield effect is a parasitic sensitivity to a magnetic field which is orthogonal to the sensing direction of the sensor. This effect is nonlinear and it is common to all magnetic sensors containing ferromagnetic material.

Why does mode jump occur in magnetron?

The oscillating frequency corresponding to the different modes are not the same. Some are quite close to one another, so that a π-mode oscillation which is normal for magnetron becomes (3/4)π mode oscillation. This is called as mode jumping. In order to avoid mode jumping strapping technique is used.

What is mode jumping in magnetron?