High power, high uniformity strip electron gun design, simulation and performance

This article discusses the simulation, design and performance of an 80 kW s trip electron gun. Electrons from an electrically heated, multisegmented ta ntalum filament are electrostatically focused to provide a sheet of electro ns in the postanode region, that when bent through 270 degrees along a circ le of radius 120 mm by a uniform magnetic field, focuses on the target. Thi s gun has been tested up to 80 kW (45 kVx1.8 A), and delivers power densiti es on the target in the range of 20 kW cm(-2). The linear current density i s uniform up to 20%, over a focal spot of dimension 80x5 mm(2). Good corres pondence between filament geometry and focal spot image of the electron bea m on the target has been obtained, which is desirable in applications invol ving metal vapor coatings. This design is scaleable along the length of the focal spot without sacrificing uniformity, which is not possible in scanni ng or multiple pencil-type of electron guns. Experimental measurement of gu n parameters such as position of filament in relation to the cathode openin g, distribution of current along the length of the beam, focal spot size, e xtraction efficiency, etc., along with data concerning electron beam qualit y as a function of various parameters, are presented. The performance of th is gun under different experimental conditions, as well as the simulation a nd modeling using an in-house three-dimensional beam dynamics code, is disc ussed. (C) 2001 American Institute of Physics.