Guest Editorial the Eighteenth Special Issue on High-Power Microwave and Millimeter-Wave Generation

The field of high-power microwave and millimeter-wave generation continues to be an active area of research and technological development to meet the demand of high peak, average, and prime power needs of government and industrial applications. High-power vacuum electronic devices, producing coherent electromagnetic radiation ranging from tens of centimeters to submillimeter wavelengths, continue to find application in advanced fusion and accelerator device applications, state-of-the-art radar and electronic countermeasures, high data-rate communications, and material processing. Advances in materials, plasmas, cathode technology, and electromagnetic structure design, as well as theory, modeling, and simulation, help to drive this technology to achieve unprecedented peak and average power, more compact size, enhanced waveform agility, greater bandwidth, and higher efficiency.