Low-Frequency Klystron for Accelerator Applications

Recent advances in computer simulation of the electron-field interaction in the high-power klystron have resulted in major improvements in klystron performance and a better agreement of calculated and measured characteristics. Designs for two klystrons to drive the four Alvarez sections of the LAMPF accelerator are presented in this paper. The output powers for the two klystrons are 0.5 and 3.0 MW at 201 MHz. The length required for the ½-MW klystron is only 3.25 m, and the 3-MW klystron requires 3.75 m due to the higher power collector. A brief description of the computer codes and logic used to achieve these designs is presented. Full-scale test cavities for the ½-MW klystron have been built, and the input cavity is being built to validate the fabrication procedures. The low-frequency, high-power problems in klystron technology are discussed. General scaling laws are derived to produce efficient, compact, narrow-band klystrons with peak output power in the megawatt range. As an example, the salient design features of a 3-MW, 100-MHz klystron are presented. A novel feature of this design is a cavity which is simultaneously excited at two frequencies. Use of such cavities could reduce construction costs and significantly improve the performance of low-frequency klystrons, which should make them more attractive as components in future heavy ion accelerators.