FRIB’s Advanced Rare Isotope Separator pushes the limits of rare isotope discovery

Researchers at FRIB are gaining new insight into the limits of nuclear existence thanks to the precision and sensitivity of the Advanced Rare Isotope Separator (ARIS). Designed to isolate and identify individual rare nuclei from an enormous number of beam particles, up to one in a quintillion—that is like finding one needle in a thousand billion haystacks. With this sensitivity, ARIS allows scientists to study some of the most extreme and short-lived forms of matter in the universe. The team published its results (“Discovery of new isotopes in the fragmentation of ⁸²Se and insights into their production”) in Physical Review C.

ARIS plays an essential role in delivering rare isotope beams to experimental areas such as the High Rigidity Spectrometer (HRS), an instrument that will serve as the core of FRIB’s fast-beam program.

In a recent experiment, FRIB researchers accelerated a world-record-intensity beam of the heaviest form of natural selenium, selenium-82, to produce and detect (using ARIS) five isotopes never before observed: scandium-63, titanium-65, titanium-66, vanadium-68, and chromium-71. 

The team also observed one atom consistent with calcium-61—a nucleus that many theoretical models had predicted may not exist. These discoveries help define the neutron dripline, the boundary beyond which nuclei can no longer bind neutrons. Mapping this limit is critical to improving our understanding of atomic nuclei and the processes that shape the universe, including the formation of heavy elements in neutron star mergers.

ARIS allows researchers to isolate and study a broad range of nuclear beams with high precision, even at very high intensities. By measuring how rare isotopes are produced and characterizing their properties, scientists gain insight into how atomic nuclei are bound and how they behave in extreme neutron-rich conditions. These data inform and refine theoretical models of nuclear structure, supporting progress in areas important to U.S., including energy, national security, and medicine.

Michigan State University (MSU) operates the Facility for Rare Isotope Beams (FRIB) as a user facility for the U.S. Department of Energy Office of Science (DOE-SC), with financial support from and furthering the mission of the DOE-SC Office of Nuclear Physics. Hosting the most powerful heavy-ion accelerator, FRIB enables scientists to make discoveries about the properties of rare isotopes in order to better understand the physics of nuclei, nuclear astrophysics, fundamental interactions, and applications for society, including in medicine, homeland security, and industry. User facility operation is supported by the DOE-SC Office of Nuclear Physics as one of 28 DOE-SC user facilities.

The U.S. Department of Energy Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of today’s most pressing challenges. For more information, visit energy.gov/science.