Speaker
Description
The mission of the APEX-LD (A Positron-Electron eXperiment - Levitated Dipole) trap is to provide a compact (~10-liter) volume of closed dipole magnetic field lines, to be used for the confinement and study of low-temperature, long-lived e+e- pair plasmas. The requirements for this application posed a number of challenges for experiment design and engineering. (These included, e.g., the need to repeatedly make and break thermal contact with cryogenically cooled components in a vacuum environment; excitation of current in the superconducting "floating coil", followed by long-duration, feedback-stabilized levitation; and a demand for robustness to repeated quenches and possible mechanical shocks). A comparable number of experiment design and engineering solutions have been found and implemented, and APEX-LD has successfully started operation, enabling the first electron experiments to commence in August 2023. This talk will outline the design of the APEX-LD systems, then present the highlights of the experiment commissioning (e.g., efficient current induction to ~0.5 T on axis, levitation times in excess of three hours, and slow/"gentle" quenching of the non-insulated HTS [high-temperature superconducting] coil). Finally, it will describe results from first experiments (i.e., magnetic field line visualizations and e- injection) and next steps for making e- plasmas and later injecting cold, dense pulses of e+.
