Past, present and future of Vacuum Electronics

For 150 years Vacuum Electronics (VE) have been the motor of technical innovation in several important application areas. They have enabled a lot of basic inventions and have dominated development and industrial growth in their application areas over more than a century. First a description of the development of vacuum tubes with special emphasis on the electron sources from the early days to the modern state of the art [1,2,3] is given. Changing application scopes from radio transmission, microwave generation, X-ray tubes, display tubes, gas lasers, gas discharge lamps and particle accelerators are addressed. Prospects for the future of standard technology are outlined: e.g. high power vacuum electronics (microwave gyrotrons), space applications of VE (long-lived microwave tubes, ion thrusters), thermionic energy converters, e-beam lithography or vacuum based high resolution characterization.