Establishing Limits for Positron Plasmas - -- Long Term Storage, Large Particle Numbers, and Cold Beams

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Phenomena involving positrons (i.e., the antiparticles of electrons) are important in many fields including astrophysics, plasma and atomic physics, and materials science. Much progress has been made recently in these areas through laboratory experiments that exploit non-neutral plasma techniques. This proposal describes a program of research to create and understand the physics of novel states of single-component positron plasmas in new regions of parameter space. A key plasma physics focus of the research is understanding and optimizing radially compressed, torque-balanced, steady states of single component plasmas. These states are created by balancing asymmetry-induced expansion and heating with rotating-field compression and cyclotron cooling. This project will use a cryogenic, high-magnetic-field trap for positron plasma and beam formation. A near-term goal is long-term confinement (i.e., days) of = 1010 positrons in an ultra-high vacuum environment for days and the creation of positron beams with an energy spread as small as 1 meV and a new generation of electrostatic positron beams. The high-capacity trap developed in this work will be used to develop a multi-cell trap to increase positron storage capacity by additional orders of magnitude. The plasmas and beams developed in this research can be expected to have broad scientific and technological impact. Applications include study of electron-positron plasmas, the creation of low-energy anti-hydrogen atoms for tests of fundamental physics, materials characterization, atomic physics, astrophysical modeling, long term storage of antimatter, and eventually, the development of portable antimatter traps. This project will be an excellent training ground for scientific and technical personnel. It will involve graduate student and post-doctoral researchers, including members of underrepresented groups at all levels. Members of the research team frequently advise academic and industrial researchers on practical implications of the research. The positron traps and beams that they have developed are now used in a number of laboratories throughout the world.