Cold-test, large signal simulator: a conformal-mesh electromagnetic field solver

Summary form only given. The Cold-Test, Large-Signal Simulation code (CTLSS) is being developed to provide an electromagnetic simulation tool that is designed to interoperate with large-signal codes employed in microwave and millimeter-wave vacuum electron device design. Recently, CTLSS has been redesigned as a conformal-mesh code to increase simulation accuracy in complex structures. The new code solves Maxwell´s equations using a multi-block, structured, non-orthogonal-grid for two classes of problems: (1) eigenvalue problems and (2) driven-frequency problems. The numerical formulation in CTLSS is based on a generalization of the Finite Integration Technique to non-orthogonal grids. The iterative solution methods, based on Jacobi-Davidson and QMR, were selected to handle non-Hermitian operators that arise when treating lossy materials. Using a conformal mesh provides greater accuracy and efficiency when modeling complex structures, compared with the stairstep discretization of structures, due to improved boundary representation and significantly improved convergence characteristics. The conformal representation of boundaries also permits accurate determination of wall-losses. This paper will summarize the current status of CTLSS development. Examples related to the design of helix TWTs and coupled-cavity TWTs will be presented.