Computer Optimization of Electron Guns Using Beam Optics Analysis

Abstract

Electron guns are used in many vacuum electron devices to convert electrical power into an electron beam. Vacuum electron RF sources are critical for national defense and many scientific and industrial applications. In an RF source, the beam energy is converted to energy in an RF wave. The electron gun is a primary component in klystrons, traveling wave tubes (TWTs), gyrotrons, and inductive output tubes. The configuration of the gun depends on many factors, including the operating voltage, current, beam size and shape, magnetic focusing circuit, power supply, and operational environment. Consequently, customized electron gun design is required for essentially every new device. Because of the large number of variables, this is often a time consuming and expensive process. A number of 2D simulation tools are available, including EGUN and TRAK. The process becomes more demanding for 3D designs. Interest in multiple beam and sheet beam guns is placing severe demands on the computational codes as well as the design engineer. 3D analysis is computationally intensive, making iterative design very expensive when performed manually. CCR is advancing this capability using the 3D finite element, adaptive mesh code beam optics analysis (BOA). Although the designs presented here are 2D, the simulations are completely 3D. While this is not necessary forthese particular designs, it establishes the process for direct transition to 3D designs. In this program, a confined flow, Pierce electron gun was designed using computer optimization.