page_title: Cavity magnetron
section_title: Heating
hierarchical_section_title: Cavity magnetron / Applications / Heating
caption_attribution_description: Magnetron in its box Deutsch: Magnetron eines Mikrowellenherdes. Unten aus dem Blechgehäuse weiß isoliert herausgeführt: 2 Anschlüsse für Heiz- und Anodenapannung. 4 gewellte Alu-Lamellen, über den Kupferzylinder gepresst, geben Abwärme an die Kühlluft ab. Oberhalb und unterhalb je ein schwarzer Ferrit-Magnetring. Goldfärbig: Dichtung aus Drahtgewirke an den Hohlleiter. Rosa Keramik (elektrisch nichtleitend und daher Strahlungsdurchlässig) und Metallkappe bilden die Antenne, die im Hohlleiter steckt, der zum Garraum führt. English: Magnetron with magnet in its mounting box - the horizontal aluminium plates aid in cooling the device by airflow from a fan Suomi: Erääntyyppinen mikroaaltouunin magnetroni Polski: Magnetron wraz z magnesami z kuchenki mikrofalowej Русский: Магнетрон в корпусе
context_page_description: The cavity magnetron is a high-powered vacuum tube that generates microwaves using the interaction of a stream of electrons with a magnetic field while moving past a series of open metal cavities. Electrons pass by the openings to these cavities and cause microwaves to oscillate within, similar to the way a whistle produces a tone when excited by an air stream blown past its opening. The frequency of the microwaves produced, the resonant frequency, is determined by the cavities' physical dimensions. Unlike other vacuum tubes such as a klystron or a traveling-wave tube, the magnetron cannot function as an amplifier in order to increase the intensity of an applied microwave signal; the magnetron serves solely as an oscillator, generating a microwave signal from direct current electricity supplied to the vacuum tube.
  An early form of magnetron was invented by H. Gerdien in 1910. Another form of magnetron tube, the split-anode magnetron, was invented by Albert Hull of General Electric Research Laboratory in 1920, but it achieved a frequency of only 30 kHz. Similar devices were experimented with by many teams through the 1920s and 1930s.
context_section_description: In microwave ovens, the waveguide leads to a radio-frequency-transparent port into the cooking chamber. As the fixed dimensions of the chamber and its physical closeness to the magnetron would normally create standing wave patterns in the chamber, the pattern is randomized by a motorized fan-like mode stirrer in the waveguide (more often in commercial ovens), or by a turntable that rotates the food (most common in consumer ovens).
caption: Magnetron from a microwave oven with magnet in its mounting box. The horizontal plates form a heat sink, cooled by airflow from a fan. The magnetic field is produced by two powerful ring magnets, the lower of which is just visible. Almost all modern oven magnetrons are of similar layout and appearance.
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