On Friday 9 December 2022, after a long period of maintenance and major upgrades, the PIAVE-ALPI complex (i.e. the two superconducting accelerators at the National Laboratories of Legnaro) began delivering a ²⁰⁸Pb beam with an energy of 1.3 GeV for an experiment using the AGATA+PRISMA apparata, in which numerous Italian and foreign researchers are involved. The improvements made made it possible to exceed the maximum energy ever achieved by the PIAVE-ALPI complex by about 10% and to deliver a high quality beam with excellent stability throughout the duration of the experiment.
This important result marks the start of AGATA+PRISMA's experimental campaign with heavy ion beams, which will continue in 2023 with other important data takings. The goal of the current measurement is to populate exotic nuclei, with many more neutrons than stable isotopes, in the region close to the magic ⁷⁸Ni double nucleus (recently discovered in the Japanese RIKEN laboratory) in order to study its structure. To achieve this, the ²⁰⁸Pb beam is fissioned in interaction with a beryllium target and the products of the nuclear reaction are identified by the PRISMA magnetic spectrometer. The gamma rays emitted by the reaction products are measured using the AGATA gamma spectrometer, a segmented germanium detector array that is the result of a European collaboration and represents the world's state-of-the-art in gamma spectroscopy. Preliminary analysis of the data shows, as indicated in the two-dimensional matrices in the figure, excellent identification of exotic nuclei in both mass and atomic number, where the production of many elements above Ni is noted. The two gamma spectra in the figure, measured in coincidence with the ions identified in PRISMA, reveal the presence of excited levels in the ⁸⁴Se (Z=34, N=50) and ⁸⁰Ge (Z=32, N=48) nuclei. Detailed analysis of the data will allow these studies to be expanded to even more exotic nuclei.