Modeling of electron beam interactions in structures with re-entrant cavities

摘要

Many vacuum electron devices are based on the interaction between an electron beam and the electromagnetic fields of resonators. Modeling and simulation of these devices became a key element in their development. The simulation code MAGY developed primarily to model gyrodevices, can treat structures which are axisymmetric and defined by a single-valued wall radius profile, rw(z). While this allows for the simulation of interaction structures consisting of simple pill box shaped cavities, it does not allow for the simulation of interaction structures with re-entrant cavities. We have developed and implemented a formulation in MAGY that can treat such cases. It consist of dividing space into a simulation region defined by a single-valued rw(z) and cavities external to this region. The fields in the cavities are expanded in modes and couple to the fields in the simulation region at the points on boundary, rw(z). The stability, convergence and accuracy issues of the new algorithm were studied. The results of MAGY simulations were compared with known analytical and numerical solutions for electron devices with external resonators. The advantages and limits of the new approach will be also discussed.