COCA: a novel 3-D FE simulator for the design of TWT's multistage collectors

In this paper, the simulator COCA, a novel fully three-dimensional (3-D) finite-element (FE) tool for the design of multistage depressed TWTs 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 fully 3-D deterministic/neural FE mesh generator, an FE Vlasov solver coupled with an electron trajectory tracer taking into account also external magnetic fields, and a postprocessing module for result restitution, including secondary electron emission effects. All the functions are interactively managed and executed by means of an especially developed user-friendly graphical user interface which controls all the various aspects of a simulation session. The results of a simulation test performed on an asymmetric collector are also reported showing excellent agreement with available measured data. The COCA simulator provides the user with flexible and effective tools to design, test, optimize, and verify innovative asymmetrical geometries for TWT collectors.

[1]  D. Perring,et al.  Three-dimensional simulation of multistage depressed collectors on micro-computers , 1995 .

[2]  Barry Joe,et al.  Delaunay versus max‐min solid angle triangulations for three‐dimensional mesh generation , 1991 .

[3]  J.A. Dayton.  A review of the suppression of secondary electron emission from the electrodes of multistage collectors , 1998, Proceedings ISDEIV. 18th International Symposium on Discharges and Electrical Insulation in Vacuum (Cat. No.98CH36073).

[4]  N. Stankiewicz,et al.  Analytical prediction and experimental verification of TWT and depressed collector performance using multidimensional computer programs , 1979, IEEE Transactions on Electron Devices.

[5]  Peter P. Silvester,et al.  Finite elements for electrical engineers: Frontmatter , 1996 .

[6]  R. M. Vaughan,et al.  Secondary emission formulas , 1993 .

[7]  H.G. Kosmahl,et al.  Modern multistage depressed collectors—A review , 1982, Proceedings of the IEEE.

[8]  R. True,et al.  A theory for coupling gridded gun design with PPM focussing , 1984, IEEE Transactions on Electron Devices.

[9]  J. Vaughan,et al.  Representation of axisymmetric magnetic fields in computer programs , 1972 .

[10]  Salvatore Coco,et al.  Automatic mesh generation by the let-it-grow neural network , 1996 .

[11]  A. N. Curren,et al.  A low-power, high-efficiency Ka-band TWTA , 1991, International Electron Devices Meeting 1991 [Technical Digest].

[12]  J. D. Wilson,et al.  Novel high-gain, improved-bandwidth, finned-ladder V-band traveling-wave tube slow-wave circuit design , 1995 .

[13]  Dale A. Force.  Calculation of secondary electron trajectories in multistage depressed collectors for microwave amplifiers , 1986 .

[14]  William H. Frey,et al.  An apporach to automatic three‐dimensional finite element mesh generation , 1985 .

[15]  J. Vaughan,et al.  A new formula for secondary emission yield , 1989 .