Simulation of crossed-field high power microwave tubes

AEA Technology has for many years used computer simulation for prediction and interpretation of the interaction of electromagnetic waves with charged particle flow. This paper focuses on one application area where computer modelling has been particularly successful in devising novel designs; namely, in the design of new variants of the high powered microwave tube known as the magnetically insulated transmission line oscillator (MILO). The MILO works by using a slow wave structure in the anode of the magnetically insulated line to generate microwaves by resonant coupling the wave field to the electron flow. The operating mechanising is similar to that of the magnetron, where electron kinetic and potential energy are fed to wave energy. The computer aided design process for the tapered MILO has been a four stage process: 1. initial design study; 2. validation, where direct comparison of PIC simulation and experimental results led to refinement of both experiment and simulation for an idealised validation configuration; 3. design optimisation using the validated software; and 4. experimental realisation of new designs. This paper surveys aspects of the work in each of these stages.