History of the Magnetron

First Magnetron

• Albert W. Hull was a professor of physics at the Worcester Polytechnic Institute and also worked at General Electric's Research Laboratory in New York. During his research in 1920, Hull invented the first magnetron. This magnetron tube was made of glass and had a wire that emitted electrons. The elections would collect on a cylindrical plate in curved paths by way of a magnetic field. This process generated energy. Hull's invention, however, produced little power and did not have many uses.

Cavity Magnetron

• In 1939, physicists Harry Boot and John Randall, working to construct a defense system for Britain, wanted to improve on the Hull's magnetron. For their magnetron, they used black copper for the tube instead of glass. They drilled holes (cavities) into the cylindrical block to achieve a certain wavelength of the microwaves being discharged. They placed their device into a powerful magnetic field. It was tested in 1940 and proved a success by producing 400 watts of power. Not long after, they improved the prototype, and the United States soon began to manufacture the cavity magnetron.

Uses

• Cavity magnetrons are still used in radar systems today. They are most commonly used in microwave ovens to heat and cook food. Certain lighting systems, such as sulfur lamps, also use magnetrons.