A perspective on RF vacuum electronics: innovations and recent advances

Summary form only given. Vacuum electronics continues as a vital technology for the generation of coherent radiation in a spectral region extending from the UHF to the infrared. Many of the advances and innovations from current R&D efforts are associated with two primary technological thrusts. First is the continuing development of fast-wave device concepts for use in heating, particle acceleration, and RF power transmission. While efficient, high-power oscillators are sufficient for heating, coherent sources are preferred for particle acceleration and radar. For these applications, the performance requirements are more strenuous, including such features as instantaneous bandwidth, stability, linearity, and noise as well as packaging. Exemplifying this thrust is the development of a second-generation of fast-wave amplifiers based on the electron cyclotron resonance and the free electron masers and the gyro-peniotron. The second thrust is defined by the creative blending of solid-state and vacuum concepts, techniques and capabilities. The microwave power module, a new transmitter archetype, highlights the benefits of this approach. More speculatively, RF vacuum microelectronics combines the advantages of electron transport in vacuum with gated emission structures derived from solid-state micro-fabrication. The advent of practical gated vacuum emitters, based on this approach, is expected to have a strong impact on RF source technology. These recent advances and new opportunities are indicative of a growth potential that confirms RF vacuum electronics as a technology fully capable of meeting the challenges of the future.