High power ubitron-klystron

Summary form only given, as follows. A coaxial ubitron is being considered as the RF driver for the Next Linear Collider (NLC). Prior simulation of a traveling-wave ubitron using a self-consistent code found that 200 MW of power and 53 dB of gain could be achieved with 37% efficiency. In a ubitron-klystron, a series of cavities are used to obtain an even tighter electron bunch for higher efficiency. A small-signal theory of the ubitron-klystron shows that gain scales with the square of the cavity separation distance. A linear stability theory has also been developed. Verification of the stability theory has been achieved using the 2-1/2-D PIC code, MAGIC, and our particle-tracing code. Saturation characteristics of the amplifier are presented using both MAGIC and a simpler self-consistent slow-timescale code currently under development. The ubitron can also operate as a compact, highly efficient oscillator. Cavities only two wiggler periods in length have yielded up to 40% RF conversion efficiency in simulation. An initial oscillator design for directed energy applications is also presented.