Research on Starting Characteristics of a Ka-Band Magnetron with Cold Secondary Emission Cathode

Cold cathode magnetron is one of the cost-effective and reliable microwave sources. It has many advantages of instantaneous start-up, long lifetime, high reliability, and being easy to realize miniaturization of the system. A cold secondary emission cathode with Tantalum (Ta) and Palladium-barium (PdBa) alloy is proposed in this paper. The Ta disk is selected as the primary emitter and could provide primary electrons by field emission. The PdBa alloy is selected as the secondary emitter and produces the secondary electrons under the back bombardment of the primary electrons. Both of them provide the current of oscillation magnetron together. The influences of Ta-disk thickness and PdBa alloy temperature on starting characteristics of cold cathode are theoretically analyzed in detail. After that, the experimental researches on magnetron with different Ta-disks and cathode temperatures are built. Based on the experimental results, with 0.05 mm Ta-ring as the primary emitter, a 20 kW Ka-band cold secondary emission cathode magnetron is produced successfully and the starting time is less than 5 seconds. The lifetime of this magnetron is more than 500 hours.