Multiple extraction cavities for high-power klystrons

The design and performance of an X-band high-power klystron amplifier utilizing an output circuit consisting of two uncoupled output cavities are described and compared with 2-D computer simulation results. It is shown that good efficiency, low RF gap gradient, relatively uniform power extraction from each cavity, and freedom from oscillations due to extraneous modes can be achieved. The change in phase relative to the RF input for the two extraction cavities is relatively small within a frequency bandwidth on the order of 1%, when the beam voltage or drive power is varied over a moderate range. For narrowband applications, where the combining of the separate outputs is desired, good combining efficiency is possible. The number of extraction cavities can be extended to obtain still higher peak powers