Stability of the University of Maryland two-cavity gyroklystron amplifier

Summary form only given, as follows. One of the most serious problems facing the development of a high-power gyroklystron amplifier is mode competition. For modes that are not cut off in the drift tube, the gyrotron acts like an oscillator; the discontinuities provided by the cavities and output window act as partial reflectors which serve to confine the modes, and diffractive Qs well over 1000 have been observed. In addition, the long effective length of the oscillator leads to an efficient interaction (at least in the linear regime). In previous work it was shown that the minimum start oscillation current for the University of Maryland two-cavity design with no loading was a few amperes. Here the effect of loading the drift section with rings of lossy dielectric was investigated. The start oscillation current was studied as a function of magnetic field. Scaling to longer tubes (more than two cavities) and higher power was also considered