Field emission from the electrodes of practical electron guns is one of the principal phenomena limiting the operating voltage of these guns. There is substantial interest in developing photoemission cathode based DC electron guns operating with cathode f ield strengths and cathode-anode voltages well beyond the present state-of-the-art. These electron sources could provide high brightness, high average current beams for energy recovering superconducting linear accelerators, for applications in next gener ation light sources, electron cooling, and electron-ion colliders. We have studied the effect of plasma-source ion implantation on the field emission behavior of large area stainless steel electrodes. Our apparatus allows operation of disc-shaped electrod e pairs with 100 cm² uniform field areas to 125 kV. The cathode electrode is biased at high voltage, and the anode is electrically isolated, permitting measurement of the field emission current from the cathode. The electrode pairs were either mechanically polished, or implanted with nitrogen ions. Two separate ion implanted electrodes have shown negligible field emission at 20 MV/m, and emission between 0.5 and 1.7 pA/cm² at 30 MV/m during multi-hour runs at high field. These electr odes showed very little conditioning effect.

This work was supported by U.S. DOE under contract DE-AC05-84ER40150 and the Office of Naval Research.

Authors: Jefferson Lab - Charles K. Sinclair, H.F. Dylla, Timothy L. Siggins
College of William and Mary - Dennis Manos, Lingling Wu, Thomas Venhaus

Abstract submitted to PAC 2001, Chicago, IL, June 18-24, 2001

Updated March 28, 2001

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