GB1383128A - Ion source - Google Patents

Abstract

1383128 Ion sources EUROPEAN ATOMIC ENERGY COMMUNITY 27 June 1972 [29 June 1971] 30115/72 Heading H1D Apparatus for producing an ion beam comprises a tubular hollow cathode 3 through which metal or gas atoms are introduced and a hollow anode through which the ion flux emerges when the apparatus is in operation, a bottle-shaped intermediate electrode 5 which surrounds the cathode and a space upstream thereof in the direction of the anode and is constricted towards the anode, means 6 for producing a magnetic field in the ion beam direction within the intermediate electrode and a focusing system which focuses the ion beam in the region of the anode, the focusing system being constructed as a magnetic lens having two serially disposed annular polepieces 10 and 11 which are situated coaxially relative to the ion beam. The discharge from the cathode 3 to the anode 4 is compressed by the field of the coil 6 to form an axial column 2 which is further compressed in the neck of the electrode 5 by the field of a coil 7. The discharge chamber formed by the electrode 5 is bounded by a disc 8 which may be used as a starting electrode and also serves to protect the insulation 9 between the cathode 3 and electrode 5 from bombardment by stray particles. Electrode parts operating at the highest temperatures are made of tungsten or tantalum, and ducts 13, 14 and 15 for liquid coolant are provided. The cathode 3 may be axially displaceable and may be provided with a mechanical follow-up system to compensate for unavoidable losses of cathode material. An alternative embodiment (Fig. 2, not shown) comprises a plurality of cathodes 3 providing a ribbon-shaped ion beam.