Dissertation: Experimental insights from the mass measurement of neutron-rich rare-earth isotopes (Jaries)
The mass of an atomic nucleus is one of its most fundamental properties. Its direct measurement gives access to the nuclear binding energy, of interest for studying nuclear structure. Its determination with high precision also impacts on the global theoretical models which predict the nuclear properties beyond the observational limits met in laboratories.
World-class mass spectrometry
The thesis work of M. Sc. Arthur Jaries was conducted at the Accelerator Laboratory of the Ģֱ within the IGISOL group, utilizing the JYLFTRAP double Penning trap setup to perform precision mass spectrometry of exotic neutron-rich rare-earth isotopes. These measurements are relevant for the modeling of the astrophysical rapid neutron-capture (r) process, responsible for more than half of the elemental abundances above iron observed in the Solar system.
“The JYFLTRAP is one of the best mass spectrometers in the world. Used together with the highly-sensitive Phase-Imaging Ion-Cyclotron-Resonance technique, it allows to determine atomic masses with a relative precision of typically one part per billion.” says Doctoral Researcher Arthur Jaries from Ģֱ.
The direct mass measurements of the 19 neutron-rich rare-earth isotopes reported in this research work pinned down and extended, with unprecedented precision, the two-neutron separation energies of the lanthanum, cerium, terbium, dysprosium and holmium isotopic chains.
“These results give insights on the nuclear structure evolution of neutron-rich exotic nuclei in the rare-earth region and provide important inputs for the astrophysical calculations, which address the formation of the rare-earth abundance peak in the r process.” explains Jaries.
Development and commissioning of HIBISCUS
In the context of new accelerator facilities being developed worldwide to push further the boundaries of experimentally reachable exotic nuclei, this research included the building and characterization of a new ion-beam cooler and buncher device, HIBISCUS. This apparatus is ultimately meant to be installed at the upcoming Facility for Antiproton and Ion Research (FAIR), in Germany, to deliver cooled and temporally short ion bunches for trap- and laser-assisted experiments. The FAIR accelerator complex will open the exploration of new territories of the nuclide chart with state-of-the-art techniques. It will offer a formidable opportunity to study and extend the knowledge on the nuclear properties of rare and extremely neutron-rich nuclei.
“HIBISCUS will have a central role at FAIR, efficiently transferring these exotic beams to its low-energy branch with an improved overall quality, while delivering them as ion bunches to the experimental setups placed downstream.” tells Jaries.
The thesis work reports on the design, characteristics and performance of the HIBISCUS device, newly commissioned offline at the Accelerator Laboratory of the Ģֱ, as a Finnish in-kind contribution to the FAIR project.
M.Sc. Arthur Jaries defends his doctoral dissertation ”Precision mass spectrometry of neutron-rich rare-earth isotopes and commissioning of HIBISCUS for preparation of exotic beams” on the Thursday 5.6.2025 at 12:00 in Ylistönrinne, auditorium FYS1. The opponent is Professor Klaus Blaum (Max Plank Institute for Nuclear Physics, Germany) and the custos is Senior Lecturer Tommi Eronen (Ģֱ). The language of the dissertation is English.
The dissertation "Precision mass spectrometry of neutron-rich rare-earth isotopes and commissioning of HIBISCUS for preparation of exotic beams" will be available in the JYX publication archive:
