Abstract: In an electron beam generating system including a cathode, a Wehnelt electrode, an anode, three groups of at least two electrically conductive rods, the rods of each group being connected to a respective one of the cathode, the Wehnelt electrode and the anode, a plurality of electrically insulating members each holding a respective rod, and a metal disc to which the insulating members are fastened in a manner to insulate each rod from the disc and from the other rods, the disc is made in the form of a circular ring provided with a central opening and at least six additional openings disposed around the central opening, the insulating members are tubular members each having a central bore and each projecting from both sides of the disc, and each rod is inserted in the bore of a respective insulating member, and extends at least partially through, and is fastened to, its respective insulating member.