Linear and nonlinear design study of the Cusptron amplifier

The powerful microwave radiation produced by the electron cyclotron maser instability in a cylindrical waveguide (gyrotron amplifier) is a well-studied problem for the case of the off-axis electron beam, but is a relative unknown for the case of the axis-rotating electron beam (interaction via the negative mass instability), a configuration which is currently attracting interest. In this paper, information provided by the linear and nonlinear analyses of this problem are combined into a detailed study and optimization of such a device, operated with an 80 keV, 15 Amp beam, at 200 kW rf power. These parameters represent the next phase of the NSWC Cusptron experiment. The combined linear and nonlinear analyses provide the following information. From the linear analysis, the authors obtain the growth rates and Doppler shifted real frequencies appropriate for the above parameter regime. They use knowledge of the real frequencies to provide start-up information for the nonlinear analysis of the problem