High Duty Factor RF Sources at 800 MHz

The proton linear accelerator for the Los Alamos Meson Physics Facility will require 45 one-megawatt, 800-MHz rf power sources. The minimum duty factor requirement is 6% (500 ¿s pulse 120 c/s); eventually, a 12% duty factor (1000 ¿s pulse 120 c/s) will be needed. The accelerator structure which is the load for the amplifier has a high Q (typically between 20,000 and 30,000); the amplifier loading is further complicated by a variable beam load which may absorb as much as 30% of the amplifier output. Triodes, klystrons, and crossedfield amplifiers all show promise for this service. The Los Alamos Scientific Laboratory is testing and comparatively evaluating these three rf systems. The systems are described in this paper and a discussion of the evaluation program is given.