“Our vision for the future builds on the ongoing, world-leading US program in nuclear science, which includes [...] making breakthroughs in our understanding of nuclei and their role in the cosmos through research at the nation’s low-energy user facilities, ATLAS, the newly constructed FRIB, the ARUNA laboratories, and key national laboratory facilities. [...] The highest priority of the nuclear science community is to capitalize on the extraordinary opportunities for scientific discovery made possible by the substantial and sustained investments of the United States. We must draw on the talents of all in the nation to achieve this goal.” (Nuclear Science Advisory Committee (NSAC) Long Range Plan 2023)
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
CeBrA demonstrator commissioned at FSU SE-SPS
A highly selective experimental setup for particle-γ coincidence experiments at the Super-Enge Split-Pole Spectrograph (SE-SPS) of the John D. Fox Superconducting Linear Accelerator Laboratory at Florida State University (FSU) using fast CeBr3 scintillators for γ-ray detection has been commissioned. A new publication reports on the results of characterization tests for the first five CeBr3 scintillation detectors of the CeBr3 Array (CeBrA) with respect to energy resolution and timing characteristics. Results from the first particle-γ coincidence experiments successfully performed with the CeBrA demonstrator and the FSU SE-SPS are also presented. The new setup enables very selective measurements of γ-decay branching ratios and particle-γ angular correlations using narrow excitation energy gates, which are possible thanks to the excellent particle energy resolution of the SE-SPS. In addition, nuclear level lifetimes in the nanoseconds regime can be determined by measuring the time difference between particle detection with the SE-SPS focal-plane scintillator and γ-ray detection with the fast CeBrA detectors. Selective excitation energy gates with the SE-SPS exclude any feeding contributions to these lifetimes. This research was supported by the National Science Foundation (NSF), United States under Grant No. PHY-2012522 (WoU-MMA: Studies of Nuclear Structure and Nuclear Astrophysics) and by Florida State University, United States. - Florida State University
CLARION2+TRINITY setup commissioned
A new Compton-suppressed HPGe and charged-particle array, CLARION2-TRINITY, has been commissioned at the FSU John D. Fox Laboratory in collaboration with Oak Ridge National Laboratory. The TRINITY charged-particle array is comprised of 64 Cerium-doped Gadolinium Aluminum Gallium Garnet (GAGG:Ce) crystals configured into five rings spanning 7–54 degrees, and two annular silicon detectors that can shadow or extend the angular coverage to backward angles with minimal γ-ray attenuation. GAGG:Ce is a non-hygroscopic, bright, and relatively fast scintillator with a light distribution well matched to SiPMs. Count rates up to 40 kHz per crystal are sustainable. Fundamental characteristics of GAGG:Ce were measured and presented in this article, including light- and heavy-ion particle identification (PID) capability, pulse-height defects, radiation hardness, and emission spectra. The CLARION2 array consists of up to 16 Compton-suppressed HPGe Clover detectors configured into four rings (eight HPGe crystal rings) using a non-Archimedean geometry that suppresses back-to-back coincident 511-keV gamma rays. The entire array is instrumented with 100- and 500-MHz (14 bit) waveform digitizers which enable triggerless operation, pulse-shape discrimination, fast timing, and pileup correction. Two examples of experimental data taken during the commissioning of the CLARION2-TRINITY system are also presented: a PID spectrum from 16O+18O fusion-evaporation, and PID and Doppler-corrected γ-ray spectra from 48Ti+12C Coulomb excitation. - University of Notre Dame
Transformation of ICEBall to fIREBall for conversion electron spectroscopy
Conversion electron spectroscopy is a valuable tool in nuclear structure studies, but the complex spectra resulting from the high density of levels in the spectra of heavy nuclei make it difficult to extract the most beneficial information from singles measurements. This work reports on the transformation of ICEBall, which was a mini-orange spectrometer that was used in coincidence with various Germanium detector arrays, to the improved fInternal conveRsion Electron Ball (fIREBall) spectrometer for the improved measurements of E0 transitions and conversion electron coefficients. A combination of FreeCAD, COMSOL, and Geant4 simulations were implemented to optimize the geometries for the magnet filters used in the spectrometer to significantly improve the efficiency of electron collection in the energy range of interest 200 keV-1 MeV. The array of six mini-orange Si(Li) detectors are to be replaced with six new, thicker Si(Li) detectors. Experimental tests reported in the corresponding publication show a peak improvement in absolute efficiency from 2.8% to 5.3% for the 482 keV K electron line in 207Bi for a single magnet filter and detector pair.
Conversion electron spectroscopy is a valuable tool in nuclear structure studies, but the complex spectra resulting from the high density of levels in the spectra of heavy nuclei make it difficult to extract the most beneficial information from singles measurements. This work reports on the transformation of ICEBall, which was a mini-orange spectrometer that was used in coincidence with various Germanium detector arrays, to the improved fInternal conveRsion Electron Ball (fIREBall) spectrometer for the improved measurements of E0 transitions and conversion electron coefficients. A combination of FreeCAD, COMSOL, and Geant4 simulations were implemented to optimize the geometries for the magnet filters used in the spectrometer to significantly improve the efficiency of electron collection in the energy range of interest 200 keV-1 MeV. The array of six mini-orange Si(Li) detectors are to be replaced with six new, thicker Si(Li) detectors. Experimental tests reported here show a peak improvement in absolute efficiency from 2.8% to 5.3% for the 482 keV K electron line in 207Bi for a single magnet filter and detector pair.
- 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
Open tenure-track position at Duke University
The Department of Physics at Duke University in Durham, North Carolina invites applications and nominations for a tenure-track position at the assistant professor level in all fields of Experimental Nuclear Physics. Current experimental and theoretical faculty at Duke University and the Triangle Universities Nuclear Laboratory (TUNL), a Center of Excellence bridging Duke, NCCU, NCSU and UNC on Duke’s campus, have active research programs in all major areas of nuclear physics. Duke faculty in related research areas study high energy collider and neutrino physics, cosmology, quantum information & instrumentation, and nuclear non-proliferation. The successful candidate should demonstrate the potential to be a recognized leader in experimental nuclear physics who will establish a distinctive, well-funded, independent research effort. Candidates should be committed to excellence in teaching, facilitating learning, and acting as a mentor and advisor for students in research.
Bardayan elected Director of ARUNA
Nuclear Science Laboratory (NSL) Director and Notre Dame Professor of Physics Dan Bardayan was recently elected as the Director of the Association for Research at University Nuclear Accelerators (ARUNA). The ARUNA laboratories and users are grateful to John D. Fox Laboratory Director and Distinguished Research Professor Ingo Wiedenhoever at Florida State University, who had been the ARUNA director since its founding in 2010. The NSL at the University of Notre Dame is a founding member of ARUNA with a strong tradition in nuclear science research and is a national leader in the education of nuclear scientists. The NSL is the research base for 5-10% of nuclear science PhD students nationwide. Congratulations to Professor Bardayan!
New Long Range Plan for Nuclear Science
The United States Nuclear Science Advisory Committee (NSAC) released "A New Era of Discovery: The 2023 Long Range Plan for Nuclear Science". This new long range plan provides a roadmap for advancing the nation's nuclear science research programs over the next decade. The U.S. Nuclear Science community releases such a plan every 5-8 years highlighting the scientific opportunities of nuclear physics today to maintain world leadership. The document also explores the impact of nuclear science on other fields and applications of the research that benefit society. Science opportunities at the ARUNA laboratories are prominently featured.