Advances in the Theory and Modeling of Linear Beam VE Amplifiers

We present an overview of the progress made by our Naval Research Laboratory (NRL)-based group over the last 25 years in the development of computational tools used in the large-signal modeling and design of linear-beam vacuum electronic (VE) amplifiers, klystrons, and traveling-wave tubes (TWTs). These tools belong to a class of codes that we call parametric beam–wave interaction (PBWI) codes, which includes family of the codes CHRISTINE and TESLA. Notable progress includes the formulation and application of an impedance matrix description of a general class of slow wave circuits, the tracking of slow or reversed particles in klystrons, parallel modeling of multiple-beam devices, linear stability analysis based on Nyquist theory, and geometrical and electrical tolerance analysis and optimization based on solutions to the adjoint equations that govern the beam–wave interaction. The impedance matrix description, in particular, has allowed the detailed effects of circuit geometry, including complex terminations, matching sections, and severs, to be included in PBWI simulations for the first time.