Session CP11: Poster Session: Fundamental Plasmas: Antimatter Plasma (2:00pm - 5:00pm)

Technical design of a compact, levitated dipole for confinement of a low-temperature, long-lived, electron-positron plasma

A low-temperature, long-lived (LTLL) electron-positron pair plasma has never been produced in a laboratory environment. Recent advances in positron sources have enabled the production of a LTLL pair plasma. In the APEX levitated dipole experiment positrons from a reactor-based source, along with equal numbers of electrons, will be trapped in a magnetic dipole field. We present technical design plans for this experiment. A closed coil wound with high-temperature REBCO superconducting tape will produce the dipole field. The closed dipole coil (floating coil) will be magnetically levitated by use of a water-cooled copper coil (lifting coil) located above the floating coil. A feedback circuit will vary the lifting coil current in response to input from three laser rangefinders. A cooled radiation shield (RS) insulates the floating coil from room temperature radiation. We estimate a total levitation time on the order of hours. The RS is segmented into eleven electrodes. ExB drift is utilized to move incoming positrons onto closed field lines. The floating coil is mechanically lifted into place and cooled by retracting into a small sub-chamber, which is then pressurized with helium to provide thermal contact with the cold faces. The superconducting charging coil is integrated into this sub-chamber, allowing the floating coil to sit on-plane with the charging coil thus enabling efficient inductive charging. Assembly and first tests with positrons are expected early 2021.   

Outgassing Measurements of 3D Printed Components for Antimatter Applications

In support of the ALPHA and ALPHA-g antihydrogen experiments, we have tested 3-d printed components for vacuum compatibility. Measurements of outgassing rates will be presented for a variety of commercially available 3d printed metals and ceramics. Results of these studies are directly applicable to ongoing efforts to construct ALPHA-g, and are also highly relevant to a variety of plasma physics experiments and satellite missions.   

A Buffer-Gas Trap for the NEPOMUC High-Intensity Low-Energy Positron Beam

The APEX collaboration aims to produce a neutral pair plasma, comprised of equal quantities of electrons and positrons, confined by the magnetic field of a levitated dipole. More than $10^{10}$ positrons are needed to achieve a short-Debye-length plasma with a volume of 10 litres and a temperature of $\sim 1$~eV, which necessitates new advances in positron accumulation. Buffer-gas positron traps have dramatically extended the scope for atomic and non-neutral plasma physics experiments involving antimatter. In these devices, a continuous beam of positrons enters a Penning-Malmberg trap, wherein inelastic collisions with low-density molecular gases promote the efficient capture of the antiparticles. We present our plans for the installation of a buffer-gas trap at the NEPOMUC neutron-induced positron source in Munich. Beyond the pair plasma experiments, an intense trap-based positron beam will also facilitate new applications, for example, the background-free measurement of positron-annihilation-induced Auger-electron spectra.