Device for producing an electron beam

A device for producing an electron beam, comprising:

• a housing, which delimits a space that is evacuatable, and comprises an electron beam outlet opening;
• an inlet structured and arranged for feeding a process gas into the space;
• and
• a planar cathode and an anode, which are arranged in the space, and between which, a glow discharge plasma is producible by an applied electrical voltage, wherein ions are accelerateable from the glow discharge plasma onto a surface of the cathode and electrons emitted by the cathode are accelerateable into the glow discharge plasma, wherein:
• a) the cathode comprises a first part made of a first material at least on an emission side, which forms a centrally arranged first surface region of the cathode;
• b) the cathode comprises a second part made of a second material, which forms a second surface region of the cathode that encloses the first surface region;
• c) the first material is electrically conductive and has a melting point Ts>1750 K;
• and
• d) the first material is heatable by impingement with accelerated ions to a temperature at which electrons escape from the first material predominantly due to thermionic emission.