A cavity magnetron is a high-powered vacuum tube that generates coherent microwaves.
Construction and operation
A cavity magnetron consists of a hot filament (cathode) kept at or pulsed to a high negative briggs & stratton magnetron 5 hp parts low voltage power supply magnetron for microwave oven potential by a high voltage direct current power supply. The cathode is built into the center of an evacuated, lobed, circular chamber. A perpendicular magnetic field is imposed by a permanent magnet. The magnetic field causes the electrons, attracted to the (relatively) positive outer part of the chamber, magnetron radar to spiral outward in a circular path rather than moving directly to this anode. super magnetron Spaced about the rim of the chamber are cylindrical microwave magnetron connection cavities. The cavities are open along their length and so connect the common cavity space. As electrons sweep past these openings they induce a resonant magnetron repair high frequency radio field in the cavity, which in turn magnetron sputtering uk causes the electrons to bunch into groups. magnetron control adapter A portion of this field is extracted with a short antenna that is connected to a waveguide (a metal tube usually of rectangular cross section). The waveguide directs who invented the magnetron tube the extracted RF energy to the load, which may be a cooking chamber in a microwave oven or a high gain antenna in the case of radar.
The size of the cavities determine the resonant frequency and so the frequency of the emitted RF energy microwaves. The frequency is thus not precisely controllable, which is not a problem in many applications such as heating (where it does magnetic field configuration magnetron magnetron shop at downtown disney sputtering not matter; usually microwave ovens are tuned at approximately 2450MHz = 2.450GHz, where the irradiated food heats up due to dielectric losses) and radar magnetron ionization (where the receiver ge microwave magnetron can be synchronised with the nonprecision cavity magnetron output). (Where precise frequencies are required, magnetron diagnosis and repair other devices such as the klystron are used.) The voltage applied and the characteristics of the cathode determine the power of the device.
Applications
Radar
- See also History of radar (Magnetron)
In radar devices the waveguide is connected to an antenna, which may be a slotted waveguide or a conical feedhorn pointing build a magnetron into a parabolic reflector. The magnetron is operated with very short high intensity pulses of applied voltage, resulting in a short pulse of microwave energy how does a magnetron electronic ignition magnetron 2m214 work microwave oven magnetron cross reference being emitted. A small portion of this energy is reflected back to the antenna and the magnetron test waveguide where it is directed to a sensitive receiver. With further signal processing the signal magnetron is ultimately displayed as a radar map on a cathode ray tube (CRT) or a liquid crystal display.
Heating
In microwave ovens the waveguide leads to a radio frequency transparent port into the cooking magnetron invention chamber. It is important that there be food in the oven when it is operated so that magnetron shop these waves are absorbed, rather than reflecting back into the waveguide where the intensity of standing waves can cause arcing. The arcing, if allowed to occur for long periods will destroy the magnetron. history of magnetron If a very small object is being microwaved for whatever low voltage magnetron power supply reason, it is probably best to add a glass of water as a sink for microwaves, although care must be taken to not "superheat" the water.
History
Influence of a magnetron on a DVD
Simple two-pole magnetrons were developed in the 1920s but gave relatively low power outputs. The cavity dc magnetron manufacturers power supply magnetron for microwave oven version (properly referred to as a resonant-cavity magnetron) proved to be far more useful.
There was an urgent need during radar development in World War II for a high-power magnetron rifle magnetron tube microwave generator that worked in shorter wavelengths - around 10 cm rather than 150 cm - available from generators of the time. It was known that a multi-cavity resonant magnetron had been developed in 1935 by Hans Hollmann in Berlin. In 1940, at Birmingham University in the UK, John Randall and Dr Harry Boot produced a working prototype similar to Hollman's cavity magnetron, but added liquid cooling and a stronger cavity. Randall and Boot soon managed to increase its power output marine magnetron 100-fold.
An early 6kW version built by G.E.C. and given to the U.S. government in September 1940 was called "the most valuable cargo ever brought to our shores" (see Tizard Mission). At the time the most powerful equivalent microwave-producer available litton magnetron in the US (a klystron) had a power of ten watts. The cavity magnetron was widely used during World War II in microwave radar equipment, and is often credited with giving Allied 20 kilowatt conventional metal ceramic magnetron radar a considerable performance advantage over German and Japanese radars, thus directly influencing the outcome of the war. Short wave 20 kw conventional metal ceramic magnetron centimetric radar, which was made possible by the cavity magnetron, allowed work magnetron for the detection of much smaller objects and the use of much smaller antennas. The combination magnetron electronic ignition of the small sized cavity magnetron, small antennas and high resolution allowed small high quality radars to be installed magnetron theory in aircraft. They could be used by maritime patrol aircraft to detect types of magnetron raytheon magnetron objects as small as a submarine periscope, which allowed aircraft to attack and destroy submerged submarines which had previously been undetectable from the air. Centimetric contour mapping radars like H2S improved magnetron electromagnetic the metal ceramic magnetron accuracy of Allied bombers used in the strategic bombing magnetron ignition campaign. microwave magnetron Centimetric gun laying radars were much more accurate than the older technology. They made the big gunned Allied battleships more deadly and along magnetron magnet with the newly developed proximity fuse made anti-aircraft guns much more dangerous magnetron and report 24 volt power supply magnetron for microwave oven to attacking aircraft. The two coupled together and used by anti-aircraft batteries, placed along on the German V-1 flying bomb flight paths to London, are credited with destroying many of the flying bombs before they reached their target.
Since then, many millions of cavity magnetrons have been manufactured; some for radar, but the vast majority for another application that was completely unanticipated at the time - the microwave oven.
Health hazards
Among more speculative hazards, at least one in particular is well known and documented. As the lens of the eye has no cooling blood flow it is particularly prone to overheating when exposed to microwave magnetron sputter source radiation. magnetron stores This heating can in turn lead to a higher incidence of cataracts in later life. A microwave oven with a warped door or poor microwave sealing can be hazardous.
References
- T. J. Morgan - RADAR - The Mechanical Age Library - Mullen - circa 1952
- A. P. Rowe: One Story of Radar - Camb Univ Press - 1948
- Dudley Saward, Bernard Lovell: A Biography - Robert Hale - 1984
See also
- Cyclotron - An atomic accelerator that also directs particles in a spiral with a transverse magnetic field.
- Klystron - A device for amplifying or generating microwaves with greater precision and control than is available from the magnetron.
- Travelling wave tube - Another microwave amplifier device, capable of greater bandwidths than a klystron
- Free electron laser - A device for amplifying or generating microwaves, infrared light, UV, and X-Rays.
- Maser - A device for generating microwaves that produces a very low noise and stable signal, a predecessor of the laser.
- Laser - A device for generating coherent light, an evolution of the maser
External link
Information
- Magnetron collection in the Virtual Valve Museum
Patents
- U.S. Patent 2315313 - Cavity resonator - H. Bushholz
- U.S. Patent 2357313 - High frequency resonator and circuit therefor -- P. S. Carter
- U.S. Patent 2357314 - Cavity resonator circuit - P. S. Carter
- U.S. Patent 2444152 - Cavity resonator circuit - P. S. Carter
- U.S. Patent 2611094 - Inductance-capacitance resonance circuit - H. B. Rex
- U.S. Patent 2408236 - Magnetron casing - P. L. Spencer magnetron sputtering
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Electronics Topics
The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The design and construction of electronic circuits to solve practical problems is part of the fields of electronic engineering, and the hardware design side of computer engineering. The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.
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