Collective ion acceleration in systems with a virtual cathode

The current status of research and development in the realm of physics and technology of collective ion acceleration in systems with a virtual cathode (VC) is reviewed. Three major acceleration methods and devices developed on their basis are considered: reflex triodes and their modifications, gas-filled vircators, and vacuum vircators with a Luce diode. Experimen- tal data are outlined and the principal physical models inter- preting these data are described. New ion acceleration techniques whose realization involves the production and disap- pearance of the VC are also discussed. All methods of collective ion acceleration are compared and the possible ways for the further development of this promising scientific field are high- lighted.