A HIGH-YIELD AND LOW-EMITTANCE POSITRON SOURCE FROM COHERENT LASER-ELECTRON COLLISIONS

A NOVEL HIGH-YIELD POSITRON SOURCE BASED ON COHERENT PAIR CREATION FROM THE COLLISION OF A HIGH POWER LASER BEAM WITH A HIGH ENERGY ELECTRON BEAM IS PLANNED FOR THIS PROJECT. THE LASER-PRODUCED POSITRONS HAVE A LOW TRANSVERSE EMITTANCE AND A NARROW SPECTRUM, PEAKING AT AN ENERGY MUCH BELOW THE PRIMARY ELECTRON BEAM ENERGY. SPIN DEPENDENT TRANSVERSE FORCES ON THE CREATED PAIR PROVIDE A NATURAL POLARIZATION SEPARATION, WHICH CAN BE UTILIZED TO PRODUCE POLARIZED POSITRONS. THE SOURCE DOES NOT USE A SOLID TARGET, THUS AVOIDING PROBLEMS ASSOCIATED WITH THE CONVENTIONAL BETHE-HEITLER PAIR CREATION PROCESS. PHASE I WILL DEVELOP ANALYTIC AND NUMERICAL TOOLS TO SIMULATE THE BEHAVIOR OF THIS PROMISING POSITRON SOURCE. THESE TOOLS WILL INCORPORATE FUNDAMENTAL PHYSICAL PROCESSES SUCH AS SPIN DEPENDENT AND QUANTUM EFFECTS, THE EFFECT OF THE LASER ON THE MOTION OF PRIMARY BEAM AND PAIR PRODUCED PARTICLES, SHOWER EVOLUTION IN THE LASER BACKGROUND, AND SPATIAL AND TEMPORAL VARIATION OF THE LASER FIELDS. PHASE I ALSO INCLUDES A STUDY OF LASER OPTICS AND MIRROR DESIGN TO MAXIMIZE COLLISION RATE. RESEARCH RESULTS WILL BE USED TO ESTABLISH THE FEASIBILITY OF THE NEW POSITRON SOURCE, AND WILL BE INVALUABLE IN THE DESIGN OF A POSITRON EXTRACTOR IN PHASE II.