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The cavity magnetron, built in 1940 by John Randall and Harry Boot at the University of Birmingham, was a small device that produced powerful microwaves and made radar far sharper. That September a British mission took a working sample to the United States, where it went into radar sets that found aircraft, ships and submarines.

John Randall and Harry Boot; Tizard Mission (1940)

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Radar sends out radio waves and times their echoes. Shorter waves give a sharper picture, but before 1940 nothing small enough for an aircraft could make them with much power. Randall and Boot's first magnetron gave about 400 watts, and improved versions soon reached thousands. The Tizard Mission, a team of British scientists led by Henry Tizard, took a 10-kilowatt sample to America in September 1940, more than a year before the United States entered the war; the best American equivalent managed about 10 watts. Before the year was out, the Massachusetts Institute of Technology had set up its Radiation Laboratory to build radars around it. Aircraft fitted with the new sets could spot a submarine's periscope, and bombers could map the ground below them through cloud.

Türkçe oku
1940'ta John Randall ile Harry Boot'un Birmingham Üniversitesi'nde geliştirdiği magnetron, güçlü mikrodalgalar üreten küçük bir cihazdı ve radarın çok daha net görmesini sağladı. Aynı yılın eylül ayında bir İngiliz heyeti çalışan bir örneğini ABD'ye götürdü. Cihaz orada uçak, gemi ve denizaltı bulan radarlara dönüştü.

Radar radyo dalgaları gönderir ve yankılarının ne kadar sürede döndüğünü ölçer. Dalga ne kadar kısaysa görüntü o kadar keskin olur; ama 1940'tan önce bir uçağa sığacak kadar küçük hiçbir cihaz, kısa dalgaları güçlü biçimde üretemiyordu. Randall ile Boot'un ilk magnetronu 400 vat kadar güç veriyordu; geliştirilen modeller kısa sürede binlerce vata ulaştı. Henry Tizard'ın başkanlığındaki İngiliz bilim insanları, yani Tizard heyeti, Eylül 1940'ta 10 kilovatlık bir örneği Amerika'ya götürdü. ABD henüz savaşa girmemişti ve elindeki en iyi benzer cihaz yalnızca 10 vat kadar güç üretebiliyordu. Yıl bitmeden Massachusetts Teknoloji Enstitüsü (MIT), bu cihazla radar yapmak için Radyasyon Laboratuvarı'nı kurdu. Yeni radarları taşıyan uçaklar bir denizaltının periskopunu görebiliyor, bombardıman uçakları bulutların altındaki araziyi haritalayabiliyordu.

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Background reading: Cavity magnetron
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Next card in the archiveThe microwave oven grew out of radar. According to the usual story, Percy Spencer, an engineer at the American firm Raytheon, noticed that a sweet in his pocket had melted while he stood near a magnetron, the part that makes a radar's microwaves. He tried popping corn next. Raytheon filed a patent in 1945 and sold the first ovens in 1947.Read next →