Progress toward and future plans for creating an electron positron plasma in a levitated dipole and in a stellarator*

Creation of a magnetically confined short-Debye-length electron-positron plasma would open a new frontier in experimental plasma physics. We report on progress toward achieving this goal. $10^{10}$ positrons are required for a 10 liter plasma with 10 Debye lengths in the system ($n \approx 10^{12}$ m$^{-3}$ and $T \approx$ 1 eV). Positrons from the NEPOMUC positron source will be trapped, cooled, and accumulated in a buffer-gas-trap, transferred to a high capacity multi-cell trap (using a 5-T magnet), and then delivered to a levitated dipole trap or a stellarator in a series of pulses. The dipole field ($B_{max} \approx$ 1-T) is produced by a light ($< 2$ kg), magnetically levitated superconducting coil ($I >$ 30 kA-t). Hour long levitation using feedback is anticipated. Annihilation gammas will be detected with 48 scintillator detectors. Recent experiments successfully injected positrons into an electron space charge (-58 V) in a prototype trap. First experiments with a levitated dipole will be in 2021. Stellarator design is underway.