Experimental Study on Long-Pulse High-Power Microwave Generation Based on GW-Level C-Band Transit-Time Oscillator Encapsulated With Compact and Lightweight Permanent Magnet

This article presents the design, simulation, and experimental demonstration of a compact and lightweight permanent magnet (CLPM)-encapsulated C-band transit-time oscillator (TTO) capable of generating GW-level long-pulse high-power microwaves (HPMs). With a magnet weight of only 80 kg and a guiding magnetic field of 0.29 T, the device addresses key challenges in miniaturized HPM sources, including limited power capacity, plasma-induced pulse shortening, and inefficient energy extraction under radial magnetic fields. Through particle-in-cell (PIC) simulations and experimental validation, several critical optimizations are implemented: a thick metal stepped foil replaced conventional sheet-type foils to reduce the maximum electric field from 0.90 to 0.66 MV/cm, a nonuniform-radius two-cavity extractor improves beam extraction efficiency and power capacity of the device, an anode cavity is introduced to suppress secondary electron-induced impedance collapse, and a large-radius collector is designed to mitigate plasma backflow and enhance thermal management. Experimental results show stable output at 1.34-GW power, 92-ns pulse duration, and 30.3% efficiency at 4.34 GHz. The device achieves a remarkable balance between miniaturization and high performance, offering a viable technical pathway for practical applications of portable HPM systems.