COCA: a novel 3D FE simulator for the design of TWTs multistage collectors

Specialized 3D numerical simulators are required to carry out the design process of asymmetrical high-efficiency TWT collectors. A Finite-Element (FE) approach has the advantage of flexibility in the treatment of realistic collector geometries, allowing an easy utilization of irregular meshes and mesh adaptation in the discretization process. In this way the user can fit better the discretized model to the design objectives. In this paper the present release of the simulator COCA, a novel 3D FE tool for the design of multistage depressed TWT´s collectors is illustrated. COCA has been developed at the University of Catania under an ESA/ESTEC project. The complete simulator consists of three main modules: a dedicated fully 3D FE mesh generator, a 3D FE Vlasov solver, including space-charge effects, with an integrated electron trajectory tracer and a post-processing module for result restitution. The tool has been specifically conceived to provide the TWT designer with a flexible and easy-to-use environment through a friendly Graphical User Interface (GUI). In fact all the simulator functions are interactively managed and executed by using the GUI window, where several menus foresee all the actions necessary to create, modify and simulate a collector. Several examples of 3D simulations of asymmetric collectors have been performed to test the simulator; the results of the tests based on geometries available in literature are in excellent agreement with the reported measured data.