NEW SOURCE OF ULTRA-COLD POSITRON AND ELECTRON-BEAMS

We have developed a new and versatile source of cold (Delta E approxim ate to 0.018 eV), low-energy (E approximate to 0-9 eV), magnetized pos itrons and electrons. Particles are extracted from thermalized, room-t emperature, single species plasmas confined in a Penning trap. Typical ly, the trap contains From 10(7) to 10(9) particles, which can be rele ased either in the form of a quasi steady-stale beam or as a pulsed be am. Of the order of 100 pulses of 10(5) positrons, each 10 mu s in dur ation, have been achieved. Size, duration and Frequency of pulses with in a pulse train are easily variable over a wide range. Cold quasi ste ady-slate electron beams with a diameter of approximate to 3 mm have a lso been achieved. Limited only by the total charge contained in the t rap, electron currents of 0.1 mu A for several milliseconds have been generated routinely. This source represents a combination of attractiv e features not previously available using any single technique. (C) 19 98 Elsevier Science B,V. All rights reserved.