The problems of increase in power, efficiency and frequency of gyrotrons for plasma investigations

Abstract In experiments aimed at the development of gyrotrons for electron-cyclotron (EC) plasma heating, output power of 2 MW at a wavelength of 3 mm was attained. The possibility of increase in frequency of millimetre-wave gyrotron operation by transition to higher EC harmonics at a fixed magnetic field by the use of high-selectivity two-resonator cavities is discussed. Outputs of over 100 kW were generated at the second and third harmonics of EC frequency. The results of calculation of pulsed magnetic systems, capable of providing the operation of near millimetre-wave long-pulsed gyrotrons, are given. The principles of increase in efficiency of gyrotrons by means of a depressed two-stage collector of electrons are discussed.