Pushing the boundaries at FRIB: High-Precision Mass Measurements Near The Driplines

Franziska Maria Maier (FRIB, East Lansing, USA)

With new radioactive-ion-beam facilities such as the Facility for Rare Isotope Beams (FRIB) becoming operational, the properties of nuclei in close proximity to the driplines are coming within reach of high-precision measurements. Within the last two years, at a fraction of FRIB’s ultimate beam intensity, we used the LEBIT facility [1] to successfully perform Penning-trap mass measurements of ²³Si [2], ¹⁰¹Sn [3], ¹⁰³Sn [4], and ²²Al [5]. These masses are critical for nuclear astrophysics and nuclear structure studies. They provide insights into the smoothness of the mass surface, help assess isospin symmetry breaking and offer valuable anchor points for nuclear models – especially for predicting properties near the driplines, where experimental data remain scarce. As FRIB ramps up its beam intensity, the production of many more nuclei will enable new and exceptional research opportunities. However, the short half-lives of many of these nuclei pose challenges for Penning-trap mass spectrometry. To overcome these, we are developing MR-ToF devices at FRIB significantly expanding FRIB’s mass measurement and mass separation capabilities [6,7].
In this contribution, I will discuss the mass measurements of ^101,103Sn, and ²³Si and highlight their significance for nuclear structure and nuclear astrophysics. Additionally, an overview of the ongoing development of FRIB’s MR-ToF devices will be provided, that will unlock new experimental possibilities at FRIB.

[1] R. Ringle, S. Schwarz and G. Bollen, Penning trap mass spectrometry of rare isotopes produced via projectile fragmentation at the LEBIT facility, IJMS 87, 349-350, 2013.
[2] F.M. Maier, et al., Exploring Isospin Symmetry Breaking in Exotic Nuclei: High-Precision Mass Measurement of ²³Si and Shell-Model Calculations of T = 5/2 Isotopes, PRC 112, 014329, 2025.
[3] C.M. Ireland, et al., The mass of ¹⁰¹Sn and Bayesian extrapolations to the proton dripline. Submitted. https://www.arxiv.org/abs/2510.11815
[4] C.M. Ireland, F.M. Maier et al., High-Precision mass measurements of ¹⁰³Sn restores smoothness of the mass surface, PRC 111, 014314 (2025).
[5] S.E. Campbell et al., Precision Mass Measurement of the Proton Dripline Halo Candidate ²²Al, PRL 131, 152501 (2024).
[6] F.M. Maier et al., A high-voltage MR-ToF mass spectrometer and separator for the study of exotic ions at FRIB. NIMA 1084, 171220, 2026.
[7] C. M. Ireland, F.M. Maier et al., Enhancing the mass resolving power in FRIB’s proposed MR-ToF mass separator and spectrometer: Addressing non-ideal conditions. Submitted. https://arxiv.org/abs/2510.11741