ICEPIC Simulation of a Strapped Nonrelativistic High-Power CW UHF Magnetron With a Solid Cathode Operating in the Space-Charge Limited Regime

This paper presents the results of particle-in- cell (PIC) simulations of a strapped nonrelativistic ultrahigh- frequency (890-915 MHz) magnetron whose geometrical and operational parameters are close to the parameters of the high- power industrial heating magnetron producing 75-100 kW of continuous-wave microwave power. Simulations of the magnetron operation are performed without artificial RF priming, but rather in natural conditions, when magnetron oscillations start to grow from electromagnetic “noise.” This approach reveals many important details of the “preoscillating” phase of the magnetron operation. It is found, for example, that the start-up time of the magnetron with a solid cathode, operating in the explosive electron emission mode, is determined by the time needed for the electron cloud formed near the cathode to reach the anode, where the fringing dc electric fields of the periodic anode structure begin to perturb the electron cloud and to facilitate the magnetron oscillations to start to grow. The PIC simulations are performed at one magnetic held (0.238 T) and a range of applied voltages, allowing the magnetron to operate in the π mode characterized by five magnetron spokes and T E₅₁-like mode of the induced electromagnetic held distribution within the resonant system of the ten-cavity magnetron.