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Cavity magnetron

key to airborne radar and microwave ovens Midlands,

A cylindrical bronze block drilled with six holes, or ‘cavities’, mounted between two square bronze plates.
Original cavity magnetron, 1940. Science Museum/ Science & Society Picture Library

The prototype of the cavity magnetron was invented by John Randall (1905-84) and Harry Boot (1917-83) at the University of Birmingham in 1940.

At that time Britain had little money or manufacturing resources to develop the magnetron on a large scale, so Prime Minister Winston Churchill agreed that Sir Henry Tizard (1885-1959) should offer the magnetron to the Americans in exchange for their financial and industrial help. The result was that the microwave-generating cavity magnetron went into mass production, enabling portable airborne radar to be carried by both American and British aircraft by early 1941.

This innovation, one of the most significant to come out of the Second World War, is now commonplace in today’s microwave ovens.

Science Museum

University of Birmingham
Key Individuals
Harry Boot, John Randall,