Microwave generators for application to particle accelerators and ion sources: Klystrons, other vacuum tubes and solid state amplifiers

Powerful radiofrequency (rf) and microwave generator are of widespread in particle accelerators and sources, for the lower voltages required by rf accelerators as compared to electrostatic ones (which have a better power efficiency). Large accelerator projects request efficiency optimization, especially promising in the case of klystrons, where efficiency is determined by the intermediate cavity tunings, and for large tube ratings (multiMW), by the self electrostatic potential of the electron beam itself. Tubes with many electron beamlets are an option to mitigate this effect. Also modern developments in computational physics offer the possibility to study and improve the klystron bunching mechanism more directly, and general features and trends are discussed. The gyrotron and applications to ion sources are also summarized.