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A flat-cathode thermionic injector for the PHERMEX Radiographic Facility

Description: The PHERMEX (Pulsed High-Energy Radiographic Machine Emitting X-rays) standing-wave linear accelerator is a high-current electron beam generator used for flash-radiography. An improved electron gun has been designed employing a flat-thermionic cathode to replace the existing Pierce-geometry gun. The flat cathode yields increased current with the same applied voltage and cathode area as the Pierce gun. The ISIS code simulations indicate a beam current of 1.5 kA at 600 kV. The new geometry also reduces the probability for high voltage breakdown in the A-K gap. A reentrant magnet captures the expanding electron beam and a bucking coil nulls cathode-tinge field. A third coil is used to optimize the extraction field profile and reduce the effect of nonlinear space charge on the beam emittance. Time-resolved measurements of beam current and voltage have been made. In addition, a streak camera was used to measure beam emittance and spatial profile. Comparisons of measurements with simulations are presented.
Date: January 1, 1993
Creator: Kauppila, T.; Builta, L.; Burns, M.; Gregory, W.; Honaberger, D.; Watson, S. (Los Alamos National Lab., NM (United States)) et al.
Partner: UNT Libraries Government Documents Department