Efficiency Enhancement of a Klystron-Like Relativistic Backward Wave Oscillator With Waveguide Reflection and Bunching Promotion

Abstract

A klystron-like relativistic backward-wave oscillator (KL-RBWO) with transverse electron beam confinement and waveguide reflection, which works well under a magnetic-field strength below that of the cyclotron resonance, is proposed. For this device operating with a low magnetic field, effective suppression of the transverse velocity of electron beams is introduced by a local electric field near the tube head, to promote modulation uniformity of electron beams. Part of the reflected microwave from the output waveguide provides feedback enhancement to the extractor, which strengthens the local standing-wave field. Owing to a stronger electric field that can interact with the electron beam in the extractor and a higher growth of fundamental harmonic current, the efficiency of the KL-RBWO is increased to 40% when guided by a magnetic field of 0.32 T, compared with that of 30% using conventional structures.INDEX TERMS High power microwaves, intense relativistic electron beams, relativistic backward-wave oscillator, Cherenkov radiation

Improved Power Capacity in a Low-Magnetic Field and High-Efficiency Transit-Time Oscillator by a Double-Gap Extractor

“…According to the theory in Reference [17], the transverse kinetic energy of electrons is increased by strong traveling wave fields under a low magnetic field, which is detrimental to the high beam-wave conversion efficiency. Therefore, low-magnetic field and high-efficiency HPM sources usually extract the energy of electron beams by standing wave fields, which is regarded as transit radiation [6], [18], [19], [20], [21]. To achieve efficient beam-wave interaction under a low magnetic field, concentrated energy extraction of electrons is usually adopted in transit radiation devices.…”

“…In addition, the fundamental harmonic current of TTO with a doublegap extractor is greater, leading to an increase in conversion efficiency. According to reference [6], the microwave power generated in the extractor can be calculated by:…”

“…High-power microwaves (HPMs) refer to electromagnetic waves with power exceeding 100 MW and wavelengths ranging from 1 mm to 1 m. They are typically generated through the interaction between intense relativistic electron beams (IREBs) and microwaves in vacuum tubes [1], [2], [3], [4], [5], [6], [7]. Driven by scientific and industrial applications, C-band HPM sources have been rapidly developed in recent years.…”