Investigation of the operating characteristics of a 12 stepped-cavity relativistic magnetron with axial extraction driven by an “F” transparent cathode using particle-in-cell simulations

Abstract

We explore the performance of a 12 stepped-cavity relativistic magnetron with axial extraction (12 stepped-cavity RMDO) driven by an “F” transparent cathode (the “F” transparent cathode is a coaxial transparent cathode with two azimuthal periods of increased thickness and which looks like the letter “F,” so we call it “F” transparent cathode) through particle-in-cell (PIC) simulations. It is shown that using the “F” transparent cathode, an electronic efficiency of 70% with gigawatt output power is obtained while reducing the axial leakage current by about 50% compared to using the usual transparent cathode. Further PIC simulations demonstrate that frequency bifurcation occurs and mode switching can be achieved using several hundred kilowatts input RF power in the 12 stepped-cavity RMDO driven by an “F” transparent cathode. For example, it was found that using an applied driver power of 180 kW for 10 ns, the operating TE31 mode can be switched to the TE41 mode. It is also found that the secondary electron and backscattered electron emission and axial leakage current were two disturbing factors for the 12 stepped-cavity RMDO when it works at a stable operation mode but when the 12 stepped-cavity RMDO works near the critical magnetic field at the boundary between two modes, these two factors would lead to the operation modes changing.

A Compact Circular Waveguide Directional Coupler for High-Order Mode Vacuum Electronic Devices

“…As the operating frequency extends to millimeter-wave and terahertz bands, the power capability reduces as the size of the interaction circuits shrinks [4]. Therefore, in order to obtain sufficient power capability and high output power, operating in high-order mode is proposed and attempted in a large number of research works [5][6][7][8][9][10][11][12]. For example, the TM 01 mode is commonly employed for BWOs [7], the TE 0n mode or higher-order TE mn mode is adopted for gyrotrons [8], and the TE n1 mode is usually utilized for the relativistic magnetrons [9].…”

“…Therefore, in order to obtain sufficient power capability and high output power, operating in high-order mode is proposed and attempted in a large number of research works [5][6][7][8][9][10][11][12]. For example, the TM 01 mode is commonly employed for BWOs [7], the TE 0n mode or higher-order TE mn mode is adopted for gyrotrons [8], and the TE n1 mode is usually utilized for the relativistic magnetrons [9]. In the research of VED system, real-time on-line monitoring of the output power is an important component.…”