Einrichtung zur Erzeugung und Formung eines Ladungsträgerstrahles

852,725. Electron beam apparatus. ZEISSSTIFTUNG, C., [trading as ZEISS, C. [Firm of]]. June 15, 1959 [June 20, 1958], No. 20333/59. Class 39(1). Apparatus for working material with a high intensity beam of charged particles includes at least one electromagnetic cylindrical lens, corrected for spherical aberration, to focus a beam of large focal aperture in an impinging beam with a sharply defined periphery at which the beam intensity decreases sharply. The apparatus includes an elongated cathode 1, Fig. 1, a control grid 2, an anode 3 and an electromagnetic cylindrical lens 4 to produce an elongated spot on the work piece 7. A further electromagnetic cylindrical lens 6 is provided to produce a rotating field in order to rotate the beam and give a working beam of effectively circular cross-section, or a second electromagnetic cylindrical lens 5, with its axis perpendicular to that of the lens 4, may be used to produce a spot of clover leaf outline. Lenses 4 and 5 are 4-pole lenses, Fig. 2, with hyperbolic pole pieces 9, 18, 16 and 17 which are embedded in synthetic resin filling material 19, or lenses 4 and 5 may be combined into a single 8-pole lens. The lenses are corrected for spherical aberration by appropriate shaping of the pole-pieces or by using auxiliary ferromagnetic members.