| Vigorous effort in recent years has been applied toward the development of microwave amplifiers for particle accelerator and phased-array radar applications. Currently, no source is able to satisfy the stringent requirements of high peak power ({dollar}>{dollar} 100 MW) and high frequency ({dollar}>{dollar} 9 GHz) while maintaining amplitude and phase stability. This dissertation reports on the design, analysis, manufacture, and testing of a high peak power X-band coaxial microwave amplifier. It is possible that a coaxial source, employing an annular electron beam within inner and outer drift tube conductors, may exceed the capabilities of current devices by increasing the available beam current, while reducing the surface fields in the microwave structures.; Experiments using a 400 keV, 7 kA, 50 ns electron beam in the coaxial geometry are detailed. The 9 cm diameter, 2 mm thick annular beam is propagated in a drift space cutoff to all TM modes at the 9 GHz operation frequency. The existence of the transmission line TEM mode, however, precludes the use of standard cavities in a klystron arrangement. Instead, a strong interaction is provided by a 16 cm long extended cavity loaded with dielectric. The design of the extended cavity is accomplished using simple traveling wave analysis. Although the cavity oscillates at a number of resonances, a single mode is selected with 10-30 kW of input power from an external magnetron. A coupler samples 25 MW of microwave power from the cavity, independently measured using a calorimeter.; Computer simulations using the particle-in-cell code MAGIC are in excellent agreement with the experimental results. In addition, simulations indicate that the prototype structure saturates, leading to only 200 MW of total microwave power at 7% efficiency. A better design for the extended cavity alleviates saturation and can produce 450 MW at 16% efficiency. Finally, a more conventional amplifier using two extended cavities is introduced. The most serious difficulty presented by the coaxial device is efficient extraction of the microwave energy, an issue that still requires further scrutiny. |
