ARC-FREE ELECTRON GUN

摘要

An electron gun that prevents undesirable arcing by providing an improved electrostatic field that generates a confined electron stream, an improved magnetic field that directs the confined electron stream to a crucible with minimal divergence, and an improved insulation on high voltage leads. The improved electrostatic field is provided by a cathode plate (20) disposed adjacent to a filament (24) and forming a cathode window (22) aligned to the filament (24). An anode plate (28) disposed adjacent to the cathode plate (20) forms an anode window (30) aligned to the cathode window (22). The cathode plate (20) and anode plate (28) form an electrostatic field and lensing effect that directs electrons emitted from the filament (24) through the cathode and anode windows with minimal divergence. The improved magnetic field is provided by a magnet having a pair of poles, a pair of extension plates each extending from the magnet poles, and a plurality of extension members that extend from the extension plates toward the path of the electron stream.