Large numbers of positrons can be accumulated and cooled in a Penning-type trap. These positron clouds can be manipulated and conditioned using plasma physics techniques, before being released from the trap to form high quality positron beams. These techniques offer a qualitatively new method for positron beam formation and manipulation that has significant advantages in efficiency, flexibility, and cost over current beam conditioning techniques. Unique capabilities include the production of ultracold beams, brightness enhancement by radial compression of the plasma prior to extraction, and simple implementation of harmonic potential bunching. (C) 2002 Elsevier Science B.V. All rights reserved.