CTLSS features supporting vacuum electron device design

Abstract

Summary form only given, as follows. The Cold-Test, Large-Signal Simulation Code (CTLSS) is being developed to provide a 3D electromagnetic simulation tool that is designed to interoperate with large-signal codes employed in microwave and millimeter-wave vacuum electron device design. In this presentation, we describe capabilities recently introduced in CTLSS that directly support features of the large-signal simulation codes CHRISTINE ID and CHRISTINE 3D. For large signal models that operate in the frequency domain, it is necessary to specify device characteristics at selected operating frequencies. A new eigensolver capability has been developed in CTLSS to determine the eigenmode fields and related parameters (phase velocity, interaction impedances & admittances, etc.) of a dispersive periodic structure at a predetermined frequency. This contrasts with the more common approach, in which the frequency of a traveling wave is computed for a specified phase advance per period (Floquet boundary condition), and results later interpolated to the frequencies of interest. The new method reduces the total computation time required to obtain parameters for the large-signal models. The CHRISTINE 3D code simulates the large-signal characteristics of slow-wave devices using a fast, parametric model that includes a fully three-dimensional representation of both particle motion and electromagnetic fields. The traveling-wave circuit field and the RF space-charge field are treated separately, but self-consistently, and in common with many existing parametric large-signal models, the space-charge fields are computed assuming that they exist only within a cylindrical pipe at the inner radius of the circuit structures. We describe a method for correcting the space-charge field to take account of the true 3D geometry, using correction terms that are precomputed from the full circuit structure using CTLSS.