Cold-test of reltron modulation section and PIC simulation study on output power and efficiency

Abstract

Parametric analysis and cold test of reltron modulation section are presented along with particle-in-cell (PIC) simulation results. A cavity is designed to have maximum separation among the three resonant modes 0, π/2, and π. Electromagnetic (EM) simulation software packages CST Microwave Studio (MWS) and MAGIC are used to obtain and compare the electromagnetic field patterns and resonant frequencies. Both the software predict the modes with identical field pattern and a difference of 1.3% to 3.8% in resonant frequency. The MAGIC code used here captures all three modes successfully. The designed cavity is fabricated and S11 is measured. The frequencies of measured S11 minima differ by 1.6% to 3.5% from the simulated values and closely match with that of the resonant modes. Furthermore, the modulation section is parametrically studied to observe the dependence of the resonant frequencies on the physical dimensions. The key parameters that govern the operating frequency and mode separation are identified. The Q factors are calculated from S11, and after that, the cavity reactance from loaded Q. Particle-in-cell (PIC) simulation results indicate that the mode separation improves overall system performance in terms of output power and efficiency. © 2019 Wiley Periodicals, Inc.