In accordance with one embodiment of the present invention, the hollow-cathode apparatus comprises a small-diameter tantalum tube with a plurality of tantalum-foil radiation shields, wherein the plurality of shields in turn comprise one or more spiral windings external to that tube and approximately flush with the open end from which electron emission takes place. The axial length of at least one of the inner windings (closer to the tantalum tube) is equal to or less than approximately half the length of the tantalum tube. An enclosed keeper surrounds the cathode. To start the cathode, a flow of ionizable inert gas, usually argon, is initiated through the cathode and out the open end. An electrical discharge is then started between the keeper and the hollow cathode. When heated to operating temperature, electrons exit from the open end of the hollow cathode.