A 1.5 megawatt, high efficiency, X-band CEM* coaxial magnetron

A new type magnetron, known as the GEM coaxial magetron, has been developed which has several major advantages over the conventional magnetrons of today. High peak power at long pulse length can be obtained at both high efficiency and with light weight, making this device especially suitable where power availability and weight are at a premium. The frequency stability of this tube is approximately a factor of 4 better than conventional magnetrons as evidenced by extremely low pushing and pulling figures. The basic principles upon which the design of the CEM coaxial magnetron is based are discussed. The design philosophy of this tube is compared to that of conventional magnetrons. In the rising-sun magnetron mode separation is the design criterion, whereas in the CEM coaxial magnetron selective mode absorption is the key to a successful design. To obtain higher peak power output, the interaction area of the rising-sun magnetron is increased axially while in the CEM coaxial magnetron the interaction space area is increased circumferentially. The electrical performance is described and a performance chart is shown. The ease of tunability of such a design is discussed.