A Multicell Trap for Positron Storage

We describe several techniques necessary for the practical implementation of a multicell Penning-Malmberg trap\footnote{J. R. Danielson {\it et al.}, Phys. Plasmas {\bf 13}, 123502 (2007).}$^,$\footnote{C. M. Surko {\it et al.}, Rad. Phys. Chem. {\bf 68}, 419 (2003).} designed to increase positron storage by orders of magnitude (e.g., to particle numbers N $\geq 10^{12}$). Experiments are done using test electron plasmas. A technique is described to move plasmas across the confining magnetic field and dump them at specific radial and azimuthal locations. Techniques are deomonstrated to fill and operate two in-line plasma cells simultaneously and to use 1 kV confinement potentials to trap 3$\times$10$^{10}$ particles. These experiments establish the capability to create, confine, and manipulate plasmas with the parameters required for a multicell trap, namely N $\geq$ $10^{10}$ in a single cell with temperatures $\leq$ 0.2 eV, plasma lengths $\sim$ 10 cm, and radii $\sim$ 0.2 cm. The design of a new structure to test the confinement of plasmas in off-axis cells is presented, as well as an improved design for a multicell positron trap for $10^{12}$ particles. Potential applications, including prospects for a portable positron trap (i.e., to replace conventional isotope and accelerator-based sources) will also be discussed.