High power microwave applications in particle accelerators

Particle accelerators are the world largest users of microwave power. These facilities have been historically the test ground for new ideas and equipment involving high power microwaves. New accelerators are been planned which will require hundreds of MW of microwave power. For these, new CW and pulsed klystron amplifiers are being design and tested spanning a frequency spectrum from 300 MHz up to 14 GHz and pick power up to 150 MW. Many of the proposed projects rely on the development of new microwave systems that are on the frontier of known technology. In this paper the author discusses a few of the characteristics of the high power microwave systems used in particle accelerators, in an attempt to offer a glimpse in the huge universe of problems addressed to by this area of research and development.