Progress Towards a Practical Multicell Positron Trap

The physics and technology of positron confinement is central to a range of applications at the forefront of antimatter science. Progress in this area has been driven by the development of a suite of novel non-neutral plasma techniques whereby up to $4\times10^9$ positrons have now been trapped and stored.\footnote{D. W. Fitzakerley et al, {\it Bull. Am. Phys. Soc.} {\bf 58}, 176 (2013).} However the next generation of experiments will require orders of magnitude more positrons. This talk describes techniques to increase storage capacity to $\geq 10^{12}$ using a novel multi-cell trap architecture.\footnote{Danielson, Weber, Surko, {\it Phys. Plasmas} {\bf 13}, 123502 (2006).}$^,$\footnote{Danielson, Hurst, Surko, AIP Conf. Proc. {\bf 1521}, 101 (2013).} Plasmas will be stored in separate Penning-Malmberg traps (``cells'') arranged in parallel off the magnetic axis to maximize use of the magnetic field volume while minimizing the required confinement voltages. Experiments with electrons in a test structure will be described to explore the basic physics and technology of the multicell concept and to set the design of a 21-cell trap for $10^{12}$ positrons. Over 50\% of a trapped plasma has been injected into an off-axis cell, and hour-long confinement of $2\times10^8$ particles has been achieved using rotating electric fields. Experiments are under way to identify the limits of the injection process and demonstrate confinement $> 10^{10}$ particles in a single off-axis cell using kilovolt confinement potentials.