An electron beam gun comprises a beam waveguide and an accelerating anode fixed thereto. The accelerating anode is connected with the aid of high-voltage insulators and through a cathode plate to a cathode assembly. The cathode assembly comprises a linear hot cathode fixed with the aid of two cathode carriers and a focussing electrode which is coaxially arranged with respect to the linear hot cathode and encompasses it with the aid of a two-sided surface. The beam waveguide is separated from the accelerating anode with the aid of rack panels which rigidly fix the accelerating anode to the beam waveguide in such a way that a space is formed therebetween. In order to hermetically separate cathode and anode parts of the projector, the accelerating anode is provided with a plate rigidly connected thereto.