“We recommend increasing investment in small-scale and mid-scale projects and initiatives that enable forefront research at universities and laboratories. […]” (Nuclear Science Advisory Committee (NSAC) Long Range Plan 2015)
The Association for Research at University Nuclear Accelerators (ARUNA) is an association of 13 university-based accelerator laboratories in the United States and the scientists performing nuclear research at them. ARUNA was founded in 2010, with the goals to optimize the use of university-based accelerator facilities, increase the opportunities for education around them, and document their scientific impact as part of the U.S. nuclear science enterprise. ARUNA members believe that the diversity of approaches represented by their laboratories is a critical asset for a field that is presently growing fast around the science opportunities offered by the Facility for Rare Isotope Beams (FRIB).
Featured Research
- Florida State University
Elusive resonance in 11B uncovered
FSU graduate student Eilens Lopez-Saavedra and her collaborators have observed the elusive near-threshold resonance in 11B. The 10Be(d,n)11B → 10Be+p experiment was performed at the Fox Lab with RESOLUT and a dedicated detector setup in inverse kinematics. The now confirmed presence of the state (resonance) is an important step toward understanding the excessively large beta-delayed proton-decay branch of 11Be, which had previously triggered lots of speculations including exotic decays of the neutron. The results were published in Physical Review Letters. - University of Notre Dame
Measurement of Low-Energy Resonance Strengths in the 18O(α,γ)22Ne Reaction
The 18O(α,γ)22Ne reaction is an essential part of a reaction chain that produces the 22Ne(α,n)25Mg neutron source for both the weak and main components of the slow neutron-capture process. A highly sensitive experiment was performed at the Sanford Underground Research Facility, in the 4850-foot underground cavity dedicated to the Compact Accelerator System for Performing Astrophysical Research (CASPAR). The experimental end station used the γ-summing High EffiCiency TOtal absorption spectrometeR (HECTOR). Compared to previous works, the new results decrease the 18O(α,γ)22Ne stellar reaction rate by as much as ≈46+6−11% in the relevant temperature range of stellar helium burning. The results were published in Physical Review Letters. - Florida State University
Resolution of a long-standing discrepancy in the 17O+12C fusion excitation function
Research by recent FSU graduate Dr. Benjamin Asher used the 'Encore' active target detector, built during his PhD, to solve a long-standing discrepancy in the fusion excitation function of the 17O+12C system. The unique properties of Encore allowed to measure a large portion of the fusion excitation function with a single beam energy, avoiding normalization issues that are usually present in this type of measurements. Ben's research found strong oscillations which have not been observed before in odd-even systems. - University of Kentucky
Probing the structure of neutrinoless double-β decay candidates with fast neutrons
Neutrinoless double-β decay (0νββ) has not been observed but evidence for this rare decay mode is being pursued in international large-scale experiments. The rates of 0νββ depend on nuclear matrix elements, which cannot be determined experimentally and, therefore, must be calculated from nuclear structure models. A focus of recent measurements at the University of Kentucky Accelerator Laboratory (UKAL) has been on providing detailed data to guide these model calculations. Gamma-ray spectroscopic measurements following inelastic neutron scattering from several 0νββ candidates and their daughters (e.g., 76Ge, which is regarded as one of the best candidates for the observation of 0νββ, and 76Se, its double-β decay daughter) have been performed. Level lifetime determinations, such as that illustrated in the accompanying plot, permit the calculation of reduced transition probabilities, which are compared with theoretical model calculations. This material is based upon work supported by the U.S. National Science Foundation under grant no. PHY-2209178. - University of Notre Dame
Lifetime measurements of excited states in 15O
In the Sun, the CNO cycle accounts for roughly 1% of the total energy production but the neutrinos it produces provide important information about the Sun’s core. Recently, the BOREXINO collaboration made the first measurement of the CNO solar neutrino flux. Nuclear physics can cross-validate these results with precise understanding of the CNO reactions. One of the largest uncertainties in the CNO chain of reactions comes from the lifetime of the excited state in 15O at Ex = 6792 keV. A new measurement of this state’s lifetime has been performed at the NSL with the Doppler-Shift Attenuation Method, yielding a lifetime of around 0.6 fs which is shown alongside literature measurements. This measurement provides the most stringent constraint on the lifetime to date and will be combined with a complete R-matrix analysis to better understand the CNO cycle. The results were published in Physical Review C. - James Madison University
Half-life measurements in p nuclei with photoactivation technique
The ground state half-lives of 69Ge, 73Se, 83Sr, 63Zn, and the half-life of the 1/2− isomer in 85Sr have been measured with high precision using the photoactivation technique at an unconventional bremsstrahlung facility that features a repurposed medical electron linear accelerator. The γ-ray activity was counted over about 6 half-lives with a high-purity germanium detector, enclosed into an ultra low-background lead shield. The high-precision half-life measurements, determined in this work, will contribute to a more accurate determination of corresponding ground-state photoneutron reaction rates, which are part of a broader effort of constraining statistical nuclear models needed to calculate stellar nuclear reaction rates relevant for p-process nucleosynthesis. - University of Kentucky
How do neutrons interact with reactor materials?
Applications ranging from energy production to homeland security to medical treatments rely on global theoretical models of how neutrons interact with nuclei over a wide range of incident neutron energies. As neutrons are the drivers of nuclear energy production processes, and the elements carbon and silicon are used as shielding and structural materials in nuclear fission and fusion reactors and in fuel and neutron moderators, these elements take on special significance. Silicon carbide, for example, is used to clad fuel and as a pellet coating that offers protection from accidents. In research performed at the University of Kentucky Accelerator Laboratory (UKAL), the energy and angle dependence of neutrons scattering from silicon and carbon have been determined. These are just two of the important materials investigated at UKAL in a collaboration of scientists and students from the University of Kentucky, the United States Naval Academy, Mississippi State University, and the University of Dallas. This research is supported by the Department of Energy Office of Science.
News and Announcements
FRIB Visiting Scholar 2022
The Facility for Rare Isotope Beams (FRIB) at Michigan State University has opened its doors holding the promise to reach the new frontiers of the nuclear chart. To perform the first user experiment with the FRIB Decay Station initiator (FDSi), Vandana Tripathi was selected as the award recipient for the 2022 FRIB Visiting Scholar Program for Experimental Science. Read more about the excitement around the first FRIB experiment and Vandana's award.
CLARION2 installed at FSU
The new CLARION2-TRINITY array was commissioned in December 2021 with a Coulomb-excitation and fusion-evaporation experiment at the John D. Fox Laboratory at Florida State University (FSU). The detector array consists of Compton-suppressed clovers, LaBr/CeBr, a new hybrid charged-particle detector consisting of annular Si and GAGG-SiPM detectors, and a zero-degree detector, which were all installed throughout 2021. Based on community talks and participation in a LECM workshop, the array is anticipated to focus on single- and multi-step Coulomb excitation, stopping powers, Recoil-in-Vacuum calibrations for g factors at FRIB, nucleon transfer reactions, fusion evaporation, and fast-timing measurements.
ARUNA Feature
NuPECC chose the ARUNA laboratories for a featured article in its Nuclear Physics News. The 10-pages article was published in the October-December 2021 issue as part of the format's laboratory portrait.