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The cavity magnetron is a high-power vacuum tube used in early radar systems and subsequently in microwave ovens and in linear particle accelerators. A cavity magnetron generates microwaves using the interaction of a stream of electrons with a magnetic field, while moving past a series of cavity resonators, which are small, open cavities in a ...
He was the leader of a group working on the cavity magnetron from April 1940 in north-west London. [7] The cavity magnetron was producing power of around 500W (E1188 version). Eric Megaw changed the design, coating the cathode with oxides (E1189 version) [ 8 ] and eight segments from six, to increase the power to 100 kW by September 1940 ...
Electrically, this is similar to the two cavity oscillator klystron with considerable feedback between the two cavities. Electrons exiting the source cavity are velocity modulated by the electric field as they travel through the drift tube and emerge at the destination chamber in bunches, delivering power to the oscillation in the cavity.
The resonant cavity magnetron continued to evolve at the Rad Lab. A team led by I.I. Rabi first extended the operation of the magnetron from 10-cm (called S-band), to 6-cm (C-band), then to 3-cm (X-band), and eventually to 1-cm (K-band). To keep pace, all of the other radar sub-systems also were evolving continuously.
The magnetron was initially limited to aircraft operating over the UK or sea, so that if the aircraft was lost the magnetron would not fall into German hands. However, as the war progressed several new uses for the magnetron were developed, notably ground-mapping systems like the H2S radar .
This was developed by John Randall (1905-1984) and Harry Boot (1917-1983) at Birmingham University. Radars that could produce clear images of distant objects played a decisive role in World War II, by bouncing powerful, ultra-short radio waves off their targets. The cavity magnetron was the first practical device for producing such waves.
Cavity resonators are widely used as the frequency determining element in microwave oscillators. Their resonant frequency can be tuned by moving one of the walls of the cavity in or out, changing its size. An illustration of the electric and magnetic field of one of the possible modes in a cavity resonator.
The anode block of the original cavity magnetron built by Randal and Boot, which provided a leap forward in radar design The history of radar (where radar stands for radio detection and ranging ) started with experiments by Heinrich Hertz in the late 19th century that showed that radio waves were reflected by metallic objects.