Focusing system for electron beam - esp. for the welding, drilling, milling, and/or hardening of workpieces

摘要

The appts. consists of an electron gun producing a beam fed through a first magnetic lens to focus the beam to a min. cross-section at an intermediate point; a second magnetic lens then focusses the beam onto the workpiece. Located between lens and point is a diaphragm restricting the cross-section of the beam. The distance of the diaphragm from the point is pref. min. 10%, esp. min. 20% of the distance from lens to the point. Diaphragm pref. has a cooling device and can be centred w.r.t. the beam, esp. for achieving the min. current impinging on the diaphragm. The beam can be sharply focussed on the workpiece in a smaller zone than can be achieved by conventional systems.