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
