The outer limits - Intense beam devices

The advent of low-impedance accelerators in the early sixties was followed rapidly by wide ranging research efforts to understand not only the physics of intense beams but also the complete range of potential applications. A major research effort has been directed toward an investigation of microwave generation using intense relativistic electron beams. Primary research efforts have followed one of two general approaches: high-voltage extension of conventional microwave tube circuits or exploitation of new techniques of power production which emphasize the relativistic character of the electron beam. Indicative of the first approach are the gigawatt klystron development at Varian and the ultra-high power magnetron work at MIT and NRL. Although a primary incentive of these efforts was the achievement of high peak power, fundamental advances have been made in the computational analysis of crossed-field devices. Within the second approach, two primary techniques for power generation have emerged; the electron cyclotron maser and the free electron laser. U.S. and Soviet activities in these areas have not only produced impressive powers at high frequency but also have provided the basis for new areas of tube research