pp.115-126 NEW EXPERIMENTS WITH BRIGHT POSITRON AND POSITRONIUM BEAMS

Abstract: After half a century of work studying the interaction of positrons with ordinary matter, there remain several interesting fundamental questions that are uniquely suitable for investigation using antimatter, and several instances where interesting views of the world could be obtained using positrons. In this paper we examine the possibilities for imaging single molecules with positrons and for looking at a possible zero-temperature or quantum phase transition associated with the sticking of slow positronium at a cold surface. We also discuss prospects for future developments of LINAC positron beams using a rare gas moderator and for detecting positronium molecules. 1. OVERVIEW The field of positron physics includes several diagnostic techniques that have become useful, although not widely acclaimed, in certain niches under the skilful hands of some talented experimenters [1,2]. The positron is a strongly perturbing probe in many cases, but after much work we have good theories of positron interactions with matter and the computers necessary for calculations corresponding to realistic experimental conditions are available. The successful niches include areas such as defects in solids, plasma physics and surface physics that are justified in their existence by good connections to other active fields of science and technology. But for a lack of intensity, beams of low energy positrons might join their cousins (photon, neutron and electron beams) as valuable and unique probes of materials. The invention of brightness enhancement and various proposals for new positron facilities including a nano-ampere positron microprobe for the Stockpile Stewardship Program at the Lawrence Livermore National Laboratory, continue to cause dreams of a new era 115 in antimatter physics. In this contribution we examine some potentially interesting experiments that would be fun to do some day