A device for generating an electron beam

The invention relates to a device (2) for generating an electron beam (4), with a base body (8) with a limited by walls cavity (12) into which flow-connected via a to the cavity (12) access (14) gas (16 ) occurs, stimulate which plasma generating means (18) for forming a plasma (20), the free electrons (22) of the plasma (20) via an output (24) of the cavity (12) (in the direction of the cavity (12) downstream acceleration electrode 46) exit, and beam shaping means (26) for the formation of free electrons (22) into an electron beam (4). The beam shaping means (26) comprise at least a first aperture (28) having at least one aperture (30) which are so arranged and designed such that the in the operating state of the device (2) in the cavity (12) formed plasma (20) a in the flow direction (6), plasma tapered portion (32) forms, on which the aperture (30) facing end surface (34) emit free electrons (22).