Spectrometry of captured highly charged ions produced following antiproton annihilations

We report the first capture and time-of-flight spectrometry of highly charged ions (HCIs) produced following annihilations of trapped antiprotons in a Penning-Malmberg trap. A multistep nested-trap technique was developed at the AEg¯IS experiment at CERN to trap and identify the annihilation-linked ions using external scintillators. The successful capture and mass analysis of helium and argon ions confirm the viability of the approach. This proof-of-principle demonstration establishes the foundation for future high-resolution mass spectrometry of recoil-filtered nuclear annihilation fragments. This methodology could enable studies of antiprotonic atom formation and cascade dynamics, allow the in-trap synthesis of radioactive HCIs, and provide a particularly sensitive probe of the neutron-to-proton composition at the outer periphery of the nucleus.