Electron Beam Processor Technology

Abstract

The generation of powerful electron beams for industrial process application has evolved from the “point source” or cylindrical beam geometry required for early radiation research and radiographic applications. “Powerful” in this sense would refer to power levels above a few kilowatts at energies of 100 keV or greater. Electron generation and acceleration are accomplished in an evacuated tube along which the accelerating voltage is distributed by means of a resistive divider; this is typically located in the pressurized environment surrounding the accelerator tube. Gases such as SF₆ or CO₂ + N₂ are used to insulate the voltage generator and accelerator structure. This cylindrically symmetric tube structure is used to deliver a pencil beam to the exit window or metal foil through which it emerges into the ambient environment, where it can be usefully applied to the workpiece. For strip application where uniform illumination of a two dimensional surface is required, an electrostatic or magnetic scanner is added which serves to distribute the cylindrical beam over a one or, if necessary, two dimensional scan. Such a configuration is shown schematically in Figure 1 (a) and is referred to as a hybrid (vacuum/pressure) approach to accelerator design.