Miniaturized P-Band MW-Level Klystron With CeSRRs for CSNS Linac Application

In this article, a metamaterial (MTM)-inspired ${P}$ -band klystron using the second harmonic bunching technology is investigated by means of theory and simulation for the China Spallation Neutron Source (CSNS) linac application. The MTM-inspired klystron includes a high-frequency structure (HFS) with a 53% volume reduction compared to conventional counterparts while keeping high power and high efficiency. The diameter reduction is achieved by loading MTM unit cells, complementary electric split ring resonators (CeSRRs), into resonant cavities. Thus, a compact five-cavity MTM-inspired HFS using CeSRRs with a second harmonic cavity (SHC) is constructed. The particle-in-cell (PIC) jointing simulation results of the HFS and the electron-optical system indicate that the MTM-inspired klystron with CeSRRs can generate 2.97 MW output power at 324 MHz with a beam voltage of 110 kV and a beam current of 47.23 A, corresponding to an electronic efficiency of 57.2% and a gain of 50.6 dB. Vacuum breakdown and thermal analyses confirm the reliability of the miniaturization technique applied to MW-level klystron at ${P}$ -band.