magnetronisähkölyönteinen

Magnetron, in particular the cavity magnetron, is a high-power vacuum tube that generates microwaves through the interaction of an electron stream with a magnetic field inside resonant cavities. It converts electrical power into microwave radiation, typically in the gigahertz range. The exact frequency is largely determined by the dimensions of the resonant cavities and the strength of the magnetic field, with standard kitchen microwave ovens operating around 2.45 GHz.

Inside the tube, a heated cathode emits electrons that are accelerated toward the anode region. A transverse magnetic field from surrounding magnets causes the electrons to follow curved paths and form microbunches. These bunched electrons transfer energy to the resonant cavities, producing microwaves. The magnetron is designed to sustain oscillations without external feedback, and its frequency stability depends on temperature and magnetic field control.

Magnetrons are widely used as compact, high-power microwave sources in radar transmitters, industrial heating, and household microwave ovens. Industrial magnetrons can deliver tens of kilowatts of continuous power or hundreds of kilowatts in pulsed operation. Microwave ovens typically employ magnetrons with output in the several hundred to about 1,000 watts range.

Performance depends on geometry and materials; efficiency is commonly around 60 percent under load, while frequency stability is modest and not suitable for precision RF applications without additional control. They are robust but require high voltages and vacuum seals, and aging can reduce power and efficiency. Control is usually achieved via the power supply or external tuning; modern ovens use inverter power supplies to improve regulation and efficiency.

The cavity magnetron emerged in the 1940s and played a pivotal role in wartime radar technology. Developers in the United Kingdom, notably John Randall and Harry Boot, contributed to its maturation, followed by rapid deployment in allied industries.