Adam Attarian

Computational Design of Asymmetric Electron Beam Devices

Three-dimensional design codes are allowing the development of more complex electron beam devices with significant performance improvements over axially symmetric devices. Distributed beam RF devices, including multiple-beam and sheet-beam designs, allow significant reduction in operating voltage with improved efficiency and bandwidth. The increased parameter space, however, makes the design process extremely complicated and costly. This paper describes optimization techniques to automate the most time-consuming tasks of the design, which is searching the available parameter space to optimize performance. Both sheet-beam and multiple-beam designs are considered.

Application of the Unscented Kalman Filtering to Parameter Estimation

Filtering is a methodology used to combine a set of observations with a model to obtain the optimal state. This technique can be extended to estimate the state of the system as well as the unknown model parameters. Estimating the model parameters given a set of data is often referred to as the inverse problem. Filtering provides many benefits to the inverse problem by providing estimates in real time and allowing model errors to be taken into account. Assuming a linear model and Gaussian noises, the optimal filter is the Kalman filter. However, these assumptions rarely hold for many problems of interest, so a number of extensions have been proposed in the literature to deal with nonlinear dynamics. In this chapter, we illustrate the application of one approach to deal with nonlinear model dynamics, the so-called unscented Kalman filter. In addition, we will also show how some of the tools for model validation discussed in other chapters of this volume can be used to improve the estimation process.

An optimizer for Beam Optics Analyzer

An automated, GUI-accessible optimizer has been implemented into Beam Optics Analyzer; the optimizer uses iterative methods to model electron guns and surface electric fields.

Design of Doubly Convergent Multiple-Beam Electron Guns

In an effort to achieve higher power RF source performance, designers are utilizing distributed beam devices, such as sheet beams and multiple beams. A limitation is the amount of current that can be emitted by the cathode while still achieving long cathode lifetimes. The desire is to develop distributed beam devices that utilize fundamental mode cavities in the RF circuit. For multiple-beam devices, where the individual beams propagate at the same radius as the cathode, a limitation is reached, where the size of the cathode becomes limited by the space available. A solution is to place the cathodes at a larger radius and compress the beams toward the radius required for fundamental mode cavities. This paper describes the design of a multiple-beam gun where the ensemble of beams is compressed toward the device axis while still achieving parallel propagation through the RF circuit.

Design of asymmetrical electron beam devices using computer optimization

Iterative computational design of asymmetrical electron beam devices, such as sheet beam and multiple beam klystrons, requires 3D analysis involving complex geometries. Manual, iterative design is extremely difficult and impractical for all but the simplest devices. Computer optimization tools and techniques are described that provide automated design of these devices using common personal computers with reasonable execution times.

Phase II Final Report Computer Optimization of Electron Guns

This program implemented advanced computer optimization into an adaptive mesh, finite element, 3D, charged particle code. The routines can optimize electron gun performance to achieve a specified current, beam size, and perveance. It can also minimize beam ripple and electric field gradients. The magnetics optimization capability allows design of coil geometries and magnetic material configurations to achieve a specified axial magnetic field profile. The optimization control program, built into the charged particle code Beam Optics Analyzer (BOA) utilizes a 3D solid modeling package to modify geometry using design tables. Parameters within the graphical user interface (currents, voltages, etc.) can be directly modified within BOA. The program implemented advanced post processing capability for the optimization routines as well as the user. A Graphical User Interface allows the user to set up goal functions, select variables, establish ranges of variation, and define performance criteria. The optimization capability allowed development of a doubly convergent multiple beam gun that could not be designed using previous techniques.

P2-31: Use of optimization for the design of electron guns

This paper describes implementation of optimization routines in the 3-D trajectory code Beam Optics Analyzer (BOA). Specifically, techniques are being developed for designing confined flow electron guns for a variety of applications, including sheet beam and multiple beam guns. The current emphasis is on design of magnetic circuits to achieve a specified magnetic field profile for immersed flow. This includes specification of coil currents and polepiece geometries. The goal functions, optimization routines, and simulation results will be presented.

Optimization for the design of electron guns

Creek Research, Inc. (CCR) is continuing development of optimization routines for design of both simple and complex electron beam devices. The principle computational tool is Beam Optics Analyzer (BOA), a 3-D finite element charged particle analysis program with electrostatic and magnetostatic solvers [1]. CCR is teamed with scientists and students at North Carolina State University to integrate advanced optimization routines into BOA. Previous reserach developed routines for optimizing cathode anode spacing to achieve a specified beam current, magnetic field registration to achieve a specified beam size, electrode geometry to minimize field gradients, and cathode shape to reduce beam ripple [2, 3].

Optimized design of 3D electron devices

Calabazas Creek Research, Inc. (CCR) and North Carolina State University (NCSU) are developing optimization techniques for designing complex, 3D electron beam devices. Traditionally, iterative simulation techniques were used to design electron guns and other devices using cylindrical symmetry. Prior to development of optimization techniques for these devices, it typically required days or months to develop final designs. Optimization techniques reduced this design time to a few 10s of hours [1, 2].

An optimizer for beam opics analyzer

An automated, GUI-accessible optimizer has been implemented into Beam Optics Analyzer; the optimizer uses iterative methods to model electron guns and surface electric fields. Beam Optics Analyzer (BOA) is an adaptive mesh, finite element, charged particle trajectory modeling tool for designing 3D electron devices. Previous research included the optimized design of Brillouin focused electron guns for traveling wave tubes and confined flow Pierce electron guns for high power devices. This research provided the foundation for the current work.