Cavity magnetron[edit]
Microwave ovens, several from the 1980s
The cavity magnetron developed by John Randall and Harry Boot in 1940 at the University of Birmingham.
The invention of the cavity magnetron made possible the production of electromagnetic waves of a small enough wavelength (microwaves). The magnetron was originally a crucial component in the development of short wavelength radar during World War II.[5] In 1937–1940, a multi-cavity magnetron was built by the British physicist Sir John Turton Randall, FRSE, together with a team of British coworkers, for the British and American military radar installations in World War II. A more high-powered microwave generator that worked at shorter wavelengths was needed, and in 1940, at the University of Birmingham, John Randall and Harry Boot produced a working prototype.[6]
Sir Henry Tizard travelled to the U.S. to offer them the magnetron in exchange for their financial and industrial help (see Tizard Mission). An early 6 kW version, built in England by the General Electric Company Research Laboratories, Wembley, London, was given to the U.S. government in September 1940. Contracts were awarded to Raytheon and other companies for mass production of the magnetron