HIGH-POWER COAXIAL UBITRON OSCILLATOR - THEORY AND DESIGN

The theory and design of a high-power coaxial ubitron oscillator is di scussed. The device utilizes a high-current annular electron beam inte racting with the radio frequence (RF) breakdown-resistant TE0.1 mode i n a coaxial cavity, Stable and laminar flow of the electrons is achiev ed without a confining axial field by using periodic permanent magnets to form the wiggler, A linear theory is derived for the cavity's star t-oscillation condition using a Vlasov analysis and a nonlinear simula tion code is described. Agreement is good between the linear theory, n onlinear code, and the 2-1/2-dimensional particle-in-cell code, MAGIC. A 1-GW, S-band oscillator design with 21% efficiency is presented. It was found that the interaction efficiency in the cavity could be incr eased to 46% using the technique of axial mode profiling.