Cold Testing of a Radial Extraction Output Cavity for a Frequency Doublin Gyroklystron

Abstract

Research in the University of Maryland Gyroklystron program has centered around the development of a 17.136 GHz gyroklystron, that combines the gyrotron mechanism with the ballistic bunching of klystrons to produce a high power, high gain amplifier. The current tube is a 4-cavity, (input, buncher, penultimate and output) coaxial, frequency doubling system that will be used as a driver for the Haimson Research Corporation (HRC) accelerator structure. This thesis presents the design, simulation, optimization, cold test methodology and performance data of a proposed radial extraction output cavity in which the microwave energy is extracted through an inner coaxial conductor in the TE01 circular mode. The positioning of dielectrics in the drift spaces and the effect of axial and radial misalignments between the inner and outer walls of the cavity were studied at depth and quantified. One advantage of this topology is that it reduces the size and complexity of the output waveguide chain otherwise needed to convert the TE02 circular mode from the gyroklystron into the standard rectangular waveguide for injection into the HRC accelerator structure. Cold test results show that this new cavity, which has a Q of 458 and a resonant frequency of 17.112 GHz, is a viable replacement for the output cavity currently in the system, as long as the cavity is well-aligned.