Patent ID: 8878422

Claim:
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 T s >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.