Description

This low voltage S-band, right-angle, slot-type magnetron consists of a cylindrical anode block with two parallel glass and metal tubes (the cathodes) protruding from one side of the cylinder. There is a small block of metal protruding from the other side of the anode block (at a right angle from the cathode pipes). There is a small cylinder (the output pipe) protruding directly opposite from the cathode pipes. The assembly is mounted on a square mounting flange that orient the cathode and output pipes parallel to the base. The anode block is cut away on one side to expose the design details in the interior. Serial number X1.

Magnetrons are high-power vacuum tubes developed for use in early radar systems. They generate short pulses of high power microwave energy from the electric current supplied to the vacuum tubes, and are at the heart of radar devices and microwave ovens, as well as a few specialized lighting systems.

In the 1930s, many believed radar would be the most important military technology in any future conflict but while long wave systems, such as those used during the Battle of Britain, had been developed, microwave (meaning wavelengths shorter than 10 cm) radar remained elusive. John Randall and Harry Boot at the University of Birmingham, England invented the resonant cavity magnetron in February 1940. With the start of World War II in Europe just a few months later in September, British officials made a startling decision to ask for technical assistance from the United States. On October 11, 1940, the MIT Radiation Laboratory was born.

The goal was simple: Figure out why the Randall and Boot device worked and figure out how to manufacture such devices in significant quantities. Everyone thought the project would take 50 scientists and engineers about one year. In five years, the Rad Lab (as the famous facility would come to be known) grew from 50 to 4,000 employees, second only to the Manhattan Project in size and importance. The Rad Lab introduced 150 different systems for radar, navigation, early warning, gun direction, and blind bombing, as well as LORAN navigation system.

Researchers at the Rad Lab and its partner Raytheon developed many magnetrons during the course of the war. This particular example is an experimental magnetron developed by the MIT Radiation Laboratory, Group 53 under the direction of Jerrold Zacharias. It is a 2J38-2J39 low voltage S-band magnetron, a fixed frequency pulsed oscillator magnetron designed for operation at a pulse power output range of 2.5 to 10 KW. The two models are mechanically identical except for an octagonal wire strap, which could be adjusted to separate the frequencies into two bands. The frequency for the 2J38 was in the band from 3245 to 3267 Mc/sec and the 2J/39 was in the band 3267 to 3333 Mc/sec. The 2J38 covers the range from 3267 to 333 MHz. An unusual feature of the construction is the octagonal wire strap. Separation of the frequencies into the two bands is achieved by adjustment of the strap.

Additional Information

For further information on this magnetron, see MIT Radiation Laboratory Series, vol. 6, p. 747.

Type

inscription

Method

engraved

Text

ZACHARIAS GR. 53