ELECTRON BEAM APPARATUS AND ELECTRON BEAM SOURCE THEREFOR

摘要

The cathode (2) of an electron beam source (1) for an electron beam apparatus consists of a metal wire with a transverse profile which is flattened at the emission side in order to reduce the directional spread in an electron beam to be emitted transversely of the wire. An attractive compromise between the high field strength required on the emissive surface and an acceptable directional spread results in a wire profile at the emission side which is formed substantially by the flat side of an ellipse having an ellipticity of approximately 2.