Design of gridded sheet beam electron gun
A sheet beam gun with spoke grid is designed with EOS [1][2]. The results between with spoke grid and without spoke grid have been compared under the same wiggler magnetic field. When there is spoke grid, the electron beam will have a strong fluctuation in the narrow planar, but will not have great impact in the broad planar.
Recent Developments on EOS 2-D/3-D Electron Gun and Collector Modeling Code
Recent developments on our electron optics simulator (EOS) are reported in this paper. EOS is the finite-element 2-D and 3-D steady-state beam trajectory codes which target problem classes, including axisymmetric guns, gridded guns, multibeam guns, and multistage depressed collectors at present. In order to improve the accuracy, to reduce computational time and computer memory consumption, and to extend the application scope, four significant advances to EOS have been made, and they are presented in this paper. The quadratic interpolation function, which has a higher accuracy than the linear interpolation function, is employed. A time-domain electrostatic model is built to simulate some transient effects. The symmetric computation algorithm and the 2-D model are applied for symmetric and axisymmetric structures to reduce the computational time and the computer memory consumption. Moreover, the results of the modified model and the original model are compared and analyzed in detail.
Analysis of passive microwave devices by using three‐dimensional tangential vector finite elements
There are two major difficulties in applying the finite element method to the analysis of microwave devices in three dimensions. One is to obtain a stable vector finite element which does not generate spurious modes, or non-physical solutions, in the numerical analysis. The other is to model efficiently the coupling of port regions and the discontinuity region. In this paper, we describe the application of two new finite element techniques, the tangential vector finite element method and the transfinite element method, for modelling three-dimensional microwave devices. The tangential vector finite element method, unlike the conventional nodal finite element methods, imposes only the tangential continuity of the vector unknown across elements' boundaries. As a result, there would be no spurious modes, and reliable solutions are obtained. The transfinite element method, which combines the modal basis functions and the finite element basis functions through the variational technique, provides an efficient way to model the open boundary nature of the device. To validate the current analysis, a low VSWR waveguide connector and two microstrip low-pass filters are analysed. Numerical results agree very well with the measurements or those obtained by other methods.