Abstract: A high beam power electron gun of the axial type, particularly useful in large-scale vacuum metallurgy plants for melting, vaporizing and heat treating. The electron gun is controllable over its entire power range, i.e., from 10% to 100% of its nominal power, while the focal length of its beam guidance lens is maintained unchanged. This lens is downstream of a cathode, a focusing electrode and a movable anode, and is provided on its upstream side with a pole shoe to which the anode is fastened and which, together with the anode, is movable as a single unit in the axial direction for controlling the power.