The first experiment at FRIB—which studied the beta-decay of calcium-48 fragments that are so unstable that they only exist for mere fractions of a second—concluded successfully. The first experiment was led by Heather Crawford of Lawrence Berkeley National Laboratory (LBNL), with participants from Argonne National Laboratory (ANL), Brookhaven National Laboratory, Florida State University, FRIB, LBNL, Lawrence Livermore National Laboratory, Louisiana State University, Los Alamos National Laboratory, Mississippi State University, Oak Ridge National Laboratory (ORNL), and the University of Tennessee Knoxville (UTK). The spokespersons for the first experiment are James “Mitch” Allmond (ORNL), Crawford (LBNL), Ben Crider (Mississippi State University), Robert Grzywacz (UTK), and Vandana Tripathi (FSU).

Watching how these exotic nuclei decay away and the products that are produced provides information critical to understand how the atomic nucleus changes from stability to the limits of existence. To perform the study, the rare isotopes were implanted into the center of a very sensitive and granular detector device known as the FRIB Decay Station initiator (FDSi). FDSi is the initial stage of an FRIB Decay Station (FDS), whose science was envisioned in the 2015 Long Range Plan for Nuclear Science.

FDSi integrates the best detectors currently available in the community for FRIB decay studies.

“FDSi is going to be central to the FRIB science program, especially in the first years of operation,” said Crawford, staff scientist at LBNL and the contact spokesperson for the first FRIB experiment. “Such a sensitive experimental device allows us to push the limits of what FRIB can produce—this first experiment is an example of that. It’s going to be very exciting to see that first particle identification for FRIB beams, and know FDSi is allowing us to characterize the decays of those drip-line nuclei.”

The drip line is the upper mass limit of existence for each element.

At its core, FDSi is a detection system that receives a beam of rare isotopes and monitors the subsequent decay emissions. Those decay emissions can include charged particles, neutrons, or photons. FDSi is modular and flexible, and the specific configuration of the charged-particle, photon, and neutron detection arrays are dependent on the science goals of each experiment.

Collaboration is key to FDSi

Scientists from ANL, FRIB, ORNL, and UTK led the collaboration to provide the FDSi instruments needed for the first FRIB scientific user experiment, with participation from members of the larger scientific community who contribute hardware and other resources.

“In designing the FDSi mechanical infrastructure, we placed an emphasis on maximizing the potential of the user community’s existing detector resources and minimizing the time required to reconfigure those resources for optimal performance and scientific output. I believe we have achieved that design goal with the added benefit that the final product is inclusive to multiple institutions. Everyone should be proud of their contribution when the first scientific results are realized,” said Allmond, staff scientist at ORNL, member of the FDSi coordination committee, project manager of the FDSi project, and co-spokesperson on the first experiment.  

The FDSi experimental program focuses on four strategic areas of FRIB: nuclear structure, nuclear astrophysics, tests of fundamental symmetries, and applications of isotopes for society. FDSi is uniquely positioned for discovery experiments at the extremes of the accessible regions due to the high sensitivity and relatively low beam-rate requirements of decay spectroscopy techniques. In addition, FDSi is able to conduct high-precision measurements for thorough characterization of emergent phenomena, which can be used to benchmark and differentiate between leading theoretical models. FDSi lays the groundwork for a future FDS, which will surpass current generation systems through recent advancements in technology.

The first FRIB experiment used a unique combination of detectors to enable the first study of an exceptional region of the nuclear chart and performed so comprehensively for the first time. It is a prototypical experiment for future FDS.

“We would like to construct FDS as soon as possible and employ the best detector technologies available to take advantage of the opportunities at FRIB,” said Grzywacz, director of the University of Tennessee/Oak Ridge National Laboratory (UT-ORNL) Joint Institute for Nuclear Physics & Applications, professor of experimental nuclear physics at UTK, spokesperson for the FDS collaboration, member of the FDSi coordination committee, and co-spokesperson of the first experiment. “With FDS, we hope to cross the current barriers of precision and sensitivity to investigate nuclei that we could only dream of in the past. We expect that FDS and other FRIB instruments will enable paradigm-changing discoveries in nuclear science and open completely new perspectives on how we understand and control the matter on a femtometer scale.”

“It is a privilege to have broad user community engagement in FDSi and that the individual institutions entrust us with their detector systems for experiments at FRIB,” said Sean Liddick, associate professor of chemistry at FRIB and in Michigan State University's Department of Chemistry and FRIB associate director for experimental science, instrument contact for FDSi at FRIB, and a member of the FDSi coordination committee.

The scientific program enabled by FDSi and the eventual FDS is well aligned with the overarching science goals that have been formulated by the broader nuclear science community. FRIB enables scientific research with fast, stopped, and reaccelerated rare isotope beams, supporting a community of 1,600 scientists from around the world.

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), supporting the mission of the DOE-SC Office of Nuclear Physics. Hosting what is designed to be 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.

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.