Input coupler for a 35 GHz gyroklystron

Summary form only given. Gyroklystron amplifiers at 35 GHz are currently being designed and operated at the Naval Research Laboratory. To couple the input signal, in a relatively broadband way, into the desired TE/sub 011/ circular cavity mode, a coaxial cavity is constructed around the right circular input cavity. The two cavities are coupled by slots cut in the shared wall. Significant analysis and cold test has been done on this device. Theoretical analysis includes a circuit model, a combined mode-matching/dipole aperture theory, and HFSS simulations. The design goals are for a resonant frequency of 35 GHz, Ohmic quality factor of over 1000, total quality factor of near 175 with over 99% mode purity. Cold test results indicate the success of the design work. Sensitivity of the cavity resonance to slot orientation, cavity length, and aperture alignment is studied. A particular problem is encountered in attempting to match in the input drive signal to the cavity. Limits on attainable match are found using conventional filter theory. The final design for the cavity will be described as well as initial tests with an injected electron beam.