The invention is a unique and substantive improvement in ion source assemblies which is able to produce a ribbon-shaped ion beam having an arbitrarily chosen breadth dimension which is at least ten times greater [and often more than thirty times greater] than its thickness dimension, the breadth and thickness dimensions of the beam being normal (i.e., perpendicular) to the Z-axis direction of travel for the ion beam. In all its embodiments, the improved ion source will comprise not less than two discrete component parts: (i) A closed, solid wall, prism-shaped arc discharge chamber having limited width and depth dimensions, and which concurrently has an arbitrarily chosen and predetermined length dimension which can be as small as 80 millimeters and alternatively exceed 3,000 millimeters in size; and (ii) A primary electron trap assembly which comprises at least an adjacently located magnetic field generating yoke subassembly able to provide a discernible quadrupole magnetic field internally within a confined cavity volume existing within the measurable dimensions of the arc discharge chamber walls.

The use of the electride form of 12CaO-7Al.sub.2O.sub.3, or C12A7, as a low work function electron emitter in a hollow cathode discharge apparatus is described. No heater is required to initiate operation of the present cathode, as is necessary for traditional hollow cathode devices. Because C12A7 has a fully oxidized lattice structure, exposure to oxygen does not degrade the electride. The electride was surrounded by a graphite liner since it was found that the C12A7 electride converts to it's eutectic (CA+C3A) form when heated (through natural hollow cathode operation) in a metal tube.

An ion source has an arc chamber and multiple electrode pairs that define a respective plasma column axis within the arc chamber. A source magnet surrounds the arc chamber and defines pole pairs, each respectively associated with the electrode pairs to confine a plasma to the respective plasma column axis. The source magnet can be an electromagnet or a permanent magnet. The electromagnet has coils and a magnetic core to define the pole pairs and confine the plasma to the respective plasma column based on a coil current supplied to the coils. The magnetic core can have movable core members to magnetically couple each of the plurality of pole pairs. The permanent magnet has a magnetic core and movable core members to selectively magnetically couple the permanent magnet to each of the plurality of pole pairs.

An ion source has an arc chamber and multiple electrode pairs that define a respective plasma column axis within the arc chamber. A source magnet surrounds the arc chamber and defines pole pairs, each respectively associated with the electrode pairs to confine a plasma to the respective plasma column axis. The source magnet can be an electromagnet or a permanent magnet. The electromagnet has coils and a magnetic core to define the pole pairs and confine the plasma to the respective plasma column based on a coil current supplied to the coils. The magnetic core can have movable core members to magnetically couple each of the plurality of pole pairs. The permanent magnet has a magnetic core and movable core members to selectively magnetically couple the permanent magnet to each of the plurality of pole pairs.