Mainz 2026 – scientific programme

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A: Fachverband Atomphysik

A 4: Highly Charged Ions and their Applications I

A 4.3: Talk

Monday, March 2, 2026, 12:15–12:30, N 25

Positron trapping and current trap design at LSym — •Maria Pasinetti, Fabian Raab, Paul Holzenkamp, Andreas Thoma, Sangeetha Sasidharan, Leonie Marzel, Sarah Placek, and Sven Sturm — MPIK, Heidelberg, Germany

LSym is a new cryogenic Penning trap experiment under development at the Max-Planck-Institut für Kernphysik in Heidelberg. Its goal is a stringent CPT test by comparing matter*antimatter properties through a high-precision measurement of the electron and positron spin precession frequencies. To this end, a single positron and a He+ ion, a proxy for the electron are trapped simultaneously, enabling a decoherence-free comparison. A positron capture technique was successfully tested in December 2024. Positrons from a weak ²²Na β⁺ source are moderated and converted into positronium in a high Rydberg state, which is then ionized inside the Penning trap, allowing the positron to be retained. The key observable is the difference in the two Larmor frequencies, determined by the charge-to-mass ratios and g-factors of the particles. These frequencies are measured with a dual Ramsey sequence, where we determine the spin projection of each particle non-destructively via the continuous Stern-Gerlach effect in a magnetic bottle. At LSym, spin-state detection occurs in the "AnalysisTrap", a five-electrode Penning trap with a ferromagnetic ring electrode that generates the required gradient. The presentation outlines the positron source concept and the current status of the AnalysisTrap fabrication and assembly.

Keywords: Penning Trap; CPT; Antimatter; Positron; Continuous Stern-Gerlach Effect