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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

High-Throughput Discovery Illuminates Design Principles and Limits for Long-Lived Charged Species in Organic Electrolytes

The chemical stability of charged molecules in all-organic redox flow batteries (RFBs) is required for the prolonged operation of these devices. Molecular engineering and electrolyte optimization are used to mitigate parasitic reactions and extend the lifetimes of the charge carriers. However, how much can structural variation extend the lifetime? To probe this query, we designed a high-throughput kinetic study of the radical cation of N-methylphenothiazinium, guided by statistical sampling and learning algorithms. Using Argonne’s autonomous discovery facility, we conducted over 6,000 kinetic experiments with robotic sample preparation, parallel kinetic measurements, and machine learning inputs, testing 188 solvent molecules selected from a space of over 540 candidates from 11 chemical classes. Algorithmic selections guided us to stable solvent candidates, which were further tested in high concentration with and without supporting electrolyte. Our findings reveal the inherent difficulty of exceeding the current state of the art through solvent variation. The desired stability is statistically rare and poorly predictable. Among the many tested, only three solvents significantly outperformed our baseline, acetonitrile─and none by more than a factor of 3─suggesting a general challenge in achieving the necessary techno-economic targets. Furthermore, we suggest that self-discharge through solvent homolysis is the cause of the observed limitations. Several structural motifs contribute to >1,000 h half-life stability including molecular simplicity, symmetry, oxidation complement, and strategic fluorination. Importantly, this workflow establishes effective assays for diagnosing and predicting oxidative stress for highly stable liquid electrolytes in all batteries.

Batteries↗
DOE OSTI2026

Direct observation of the superallowed α-decay of 104 Te

The radioactivity of the α particle is among the most compelling evidence for the existence of cluster structures in atomic nuclei. During the decay process, a pre-existing α particle tunnels through the potential barrier formed by the residual nucleus1,2. The degree of preformation of the α particle, a strongly bound system of two protons and two neutrons, is extracted from the data by dividing the α-decay probability by the barrier penetrability for a given particle energy. The preformation probability changes rapidly near nuclear shell closures, which is direct evidence that clustering is connected to nuclear structure3. Enhanced preformation was observed in the lightest α-particle emitters, spherical tellurium and xenon isotopes decaying to magic isotopes of tin. Here we show the most extreme case of α-particle preformation from the measurement of the decay of tellurium-104 (104Te). With a half-life of , 104Te is the fastest ground-state α-emitting nucleus known so far. The deduced preformation demonstrates that the enhancement is greater for 104Te than for any other nucleus. One nuclear model that can explain our observation postulates that the α particle can exist only in the low-nuclear-matter-density regions on the surface of the nucleus. The uniquely high preformation for 104Te is attributed to its relation to doubly magic tin-100 (100Sn), creating conditions conducive to form an α particle.

Cox, Ian↗
DOE OSTI2026

Quantification of trace iodine using laser-induced breakdown spectroscopy for real-time monitoring of nuclear off-gas streams

This study evaluated the potential of laser-induced breakdown spectroscopy (LIBS) for real-time monitoring of trace gas-phase iodine, which is an element of high significance in nuclear applications due to its long radioactive half-life (as iodine-129), volatility, and biological impact. In anticipation of iodine evolving into off-gas systems in molten salt reactor and nuclear fuel recycling applications, this research aimed to assess LIBS performance in flowing argon and helium matrices; optimize measurement parameters using a multichannel spectrometer; and perform calibrations to assess predictive capabilities and limits of detection (LODs). Experimental results successfully measured gas-phase iodine in flowing argon and helium; however, trace iodine was not detected in air. Optimal delay times were determined to be 10 µs for argon and 1 µs for helium, which are consistent with the expected shorter plasma lifetime in helium relative to argon. An emission line survey was provided with the 206.16, 804.37, 902.24, and 905.83 nm peaks, which were identified as the strongest emission peaks. Calibration models were successfully built in both helium and argon, achieving LODs down to 3 ppm in helium and 5 ppm in argon. The iodine emission at 905.83 nm emerged as the most robust for calibration and was subsequently applied to a time series dataset in argon. The predictive trace confirmed the feasibility of employing LIBS for continuous, online quantification of trace iodine in flowing gas systems.

Andrews, Hunter B. [Oak Ridge National Laboratory ↗
DOE OSTI2025

Observation of a new isomer in {sup 185}Au

Delayed γ-ray spectroscopy of 185Au was studied at the Argonne Gas-Filled Analyzer. A new isomer at an excitation energy of 1504.2(4) keV with a half-life of 630(80) ns was identified via γ-γ coincidence analysis, decaying via a 294.8(3) keV transition. Based on Weisskopf estimates, the multipolarity of the 295 keV transition is assigned to be E1, M1, E2, or M2. Possible configurations for this new isomer are discussed based on configuration-constrained potential energy surface calculations.

Fu, X. Y.↗
DOE OSTI2026

Lifetimes of two- and four-neutron-hole states in 204 Pb and 206 Pb

The centroid-shift method was used to determine half-lives of excited levels in 204 Pb and 206 Pb. For the states with 𝐼 𝜋 = 12 + , 17 − , and 19 − in 204 Pb, values of 𝑇 1/2 = 4.9⁢(3), 3.9(3), and 0.9(3) ns, respectively, were determined. The half-life of the 𝐼 𝜋 = 9 − level in 206 Pb was measured to be 1.1(3) ns. In 204 Pb, the 12 + state arises from two neutron holes in the 𝑖 13/2 subshell, while the 17 − and 19 − levels are built on 𝜈⁡(𝑖$^{−3}_{13/2}$, 𝑝$^{−1}_{1/2}$) and 𝜈⁡(𝑖$^{−3}_{13/2}$, 𝑓$^{−1}_{5/2}$) four-neutron-hole configurations, respectively. The 9 − state in 206 Pb results from a 𝜈⁡(𝑖$^{−1}_{13/2}$, 𝑓${−1}_{5/2}$) excitation. As a result, the transition probabilities for the decay of these isomeric levels are reasonably consistent with the expected single-particle values, and these states are described well by shell-model calculations using the kshell code with the KHHE interaction.

190 ≤ A ≤ 219↗
DOE OSTI2026

First Results on the Search for Lepton Number Violating Neutrinoless Double-𝛽 Decay with the LEGEND-200 Experiment

The LEGEND Collaboration is searching for neutrinoless double-beta (0⁢𝜈⁢𝛽⁢𝛽) decay by operating high-purity germanium detectors enriched in 76 Ge in a low-background liquid argon environment. Building on key technological innovations from the GERmanium Detector Array (GERDA) experiment and the MAJORANA DEMONSTRATOR experiment, LEGEND-200 has performed a first 0⁢𝜈⁢𝛽⁢𝛽 decay search based on 61.0 kg yr of data. Over half of this exposure comes from our highest performing detectors, including newly developed inverted-coaxial detectors, and is characterized by an estimated background level of 0.5$^{+0.3}_{−0.2}$ ⁢cts/(keV ton yr) in the 0⁢𝜈⁢𝛽⁢𝛽 decay signal region. A combined analysis of data from GERDA, the MAJORANA DEMONSTRATOR, and LEGEND-200, characterized by a 90% confidence level exclusion sensitivity of 2.8 ×10 26 yr on the half-life of 0⁢𝜈⁢𝛽⁢𝛽 decay, reveals no evidence for a signal and sets a new observed lower limit at 𝑇$^{⁢0𝜈}_{1/2}$ > 1.9 × 10 26 yr (90% confidence level). Assuming the decay is mediated by Majorana neutrinos, this corresponds to an upper limit on the effective Majorana mass in the range 𝑚 𝛽⁢𝛽 < 75–200 meV, depending on the adopted nuclear matrix element.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Beta-Decay Half-Lives beyond 54 Ca: A Systematic Survey of Decay Properties Approaching the Neutron Dripline

In an experiment performed at the Facility for Rare Isotope Beams (FRIB) using the FRIB Decay Station initiator, 15 new half-lives of isotopes near 54 Ca were measured. A new method of extracting lifetimes from experimental data, taking into account the unknown 𝛽-delayed neutron emission branches of very neutron-rich nuclei, was developed to enable systematic uncertainty analysis. The experiment observed a dramatic change in the half-life systematics for the isotopes with neutron number 𝑁 = 34. Beyond 𝑁 = 34, the decline of nuclear lifetime is much slower, leading to longer than anticipated lifetimes for near-dripline nuclei. State-of-the-art shell-model calculations can explain the experimental results, revealing the imprint of shell effects and the need for modification of single-particle neutron states. In conclusion, the results from a newly developed quasiparticle random phase approximation model with potential for making global predictions were also tested against the experimental results and good agreement was found.

Physics - Nuclear physics and radiation physics↗
DOE OSTI2025

Core-excited microsecond isomer in 207 Pb

An isomeric state with T 1/2 = 1.46(10) μs and E x = 8835 keV has been established in 207 Pb. Here, this state likely arises from the occupation of neutron holes in the high-j i 13/2 and j 15/2 subshells following the excitation of the 208 Pb core. The high-spin excited level structure of 207 Pb has been extended beyond the previously known states up to E x ≈ 6 MeV. Additionally, a more precise value of the half-life of the I π = 10 + isomer in 208 Pb has been obtained. Shell-model calculations provide a good account of the structure up to the 31/2 + level in 207 Pb, while the energies of higher-spin states built from exclusively high-j nucleons are considerably underestimated.

190 ≤ A ≤ 219↗
DOE OSTI2025

Neutron matter from local chiral effective field theory interactions at large cutoffs

Neutron matter is an important many-body system that provides valuable constraints for the equation of state (EOS) of neutron stars. Neutron-matter calculations employing chiral effective field theory (EFT) interactions have been extensively used for this purpose. Among the various many-body methods, quantum Monte Carlo (QMC) methods stand out due to their nonperturbative nature and the achievable precision. However, QMC methods require local interactions as input, which leads to the appearance of stronger regulator artifacts compared to nonlocal interactions. To circumvent this, we employ large-cutoff interactions derived within chiral EFT (400 MeV ≤ Λ 𝑐 ≤ 700MeV) for studies of pure neutron matter. These interactions have been adjusted to nucleon-nucleon scattering phase shifts, the triton binding energy, as well as the triton 𝛽-decay half-life. We find that regulator artifacts significantly decrease with increasing cutoff, leading to a significant reduction of uncertainties in the neutron-matter EOS. We discuss implications for the symmetry energy and demonstrate how our new calculations lead to a reduction in the theoretical uncertainty of predicted neutron-star radii by up to 30% for low-mass stars.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Surrogate models for linear response

Linear response theory is a well-established method in physics and chemistry for exploring excitations of many-body systems. In particular, the quasiparticle random-phase approximation (QRPA) provides a powerful microscopic framework by building excitations on top of the mean-field vacuum; however, its high computational cost limits model calibration and uncertainty quantification studies. Here, we present two complementary QRPA surrogate models and apply them to study response functions of finite nuclei. One is a reduced-order model that exploits the underlying QRPA structure, while the other utilizes the recently developed parametric matrix model algorithm to construct a map between the system’s Hamiltonian and observables. Our benchmark applications, the calculation of the electric dipole polarizability of 180 Yb and the 𝛽-decay half-life of 80 Ni, show that both emulators can achieve 0.1%–1% accuracy while offering a 6–7 orders of magnitude speedup compared to state-of-the-art QRPA solvers. These results demonstrate that the developed QRPA emulators are well positioned to enable Bayesian calibration and large-scale studies of computationally expensive physics models describing the properties of many-body systems.

Beta decay↗
DOE OSTI2025

Picosecond lifetime measurements of resonances using a thick-target invariant-mass technique

Here, a new technique is presented for measuring the half-lives of resonances in the picosecond range using presently available invariant-mass apparatus and a thick target. For short-lived resonances, the energy losses of the decay fragments in the target material change their relative velocities giving rise to a poor invariant-mass resolution. However, for longer-lived resonances that travel through the remaining target material before decaying outside of the target, this dominant contribution to the resolution is eliminated. The measured invariant-mass peak will then display a narrow peak from these events which sits on a wider structure associated with the remaining events that decay in the target. The fraction of the events in the narrow peak is related to the probability that the resonance leaves the target before decaying and hence is related to the lifetime. This technique is exercised for the 2.685-MeV resonance in 33 Cl which decays by emitting an f -wave proton. A half-life of T 1/2 =5.7$^{+4.1}_{-2.5}$ ps was measured which is consistent with values inferred from other known properties of this resonance.

lifetimes & widths↗
DOE OSTI2026

Characterization of the First Prototype of the L1K65n Differential-Output Charge-Sensitive Preamplifier ASIC for High-Performance, Low-Background HPGe Detector Readout

Next-generation neutrinoless double-beta (0νββ) decay searches require a large detector/isotope mass and very low radioactive backgrounds. The upcoming LEGEND-1000 experiment (Large Enriched Germanium Experiment for Neutrinoless double-beta Decay) constitute a ton-scale array of several hundred high-purity germanium (HPGe) detectors enriched in 76Ge, the isotope of interest. It aims to reach a sensitivity beyond 10 28 years on the 0νββ decay half-life of 76Ge, necessitating an order of magnitude reduction in background with respect to the state of the art. This will require the implementation of a dedicated application specific integrated circuit (ASIC) preamplifier that will significantly lower background contribution compared to the conventional low-mass front end (LMFE) employed in the Majorana Demonstrator and LEGEND-200 experiments while maintaining or improving energy resolution and other performance parameters. Features include a high (9 MeV) dynamic range with noise low enough to achieve a trigger threshold of <1 keV, a single power supply to reduce background-inducing cabling, and a differential output to maintain signal integrity over several meters of transmission line. The chip would be optimized to operate in liquid argon (87 K) and be able to do so reliably for ten years. Following on from an earlier 180-nm prototype, we have developed a differential-output charge-sensitive preamplifier ASIC fabricated in a 65-nm process, 1×2 mm in size, that addresses these needs. Here, we present recent results from the successful testing and characterization of the first version of this device.

ASIC↗
DOE OSTI2025

Constraints on lepton number violation with the 2 tonne · year CUORE dataset

Matter-antimatter asymmetry underlines the incompleteness of the current understanding of particle physics. Neutrinoless double-beta decay (0νββ) may help explain this asymmetry while unveiling the Majorana nature of the neutrino. The CUORE (Cryogenic Underground Observatory for Rare Events) experiment searches for 0νββ of 130 Te using a tonne-scale cryogenic calorimeter operated at milli-kelvin temperatures. We report no evidence of 0νββ and place a lower limit on the half-life of T 1/2 > 3.5 × 10 25 years (90% credibility interval) with over 2 tonne·years of TeO 2 exposure. Finally, the tools and techniques developed for this result and the 5-year stable operation of nearly 1000 detectors demonstrate crucial infrastructure for future-generation experiments capable of searching for 0νββ across multiple isotopes.

Adams, D. Q. [Department of Physics and Astronomy,↗
DOE OSTI2026

Evidence for an isomeric {pi}½{sup +}[411] state in {sup 183}Ta

We report on the identification of a new isomeric state in Ta populated via the ground-state -decay of Hf. The experiment was performed at the KISS setup at RIKEN, where neutron-rich hafnium isotopes were produced via multi-nucleon transfer (MNT) reactions, followed by laser ionization of hafnium atoms, mass separation, and detection using an electron-gamma coincidence system. Isomeric spectroscopy was carried out by gating on different electron-gamma time correlations. A 459.1 keV -ray transition was identified in delayed spectra, and a half-life of μ was extracted through time-distribution fitting. The 459.1 keV state in Ta is known from previous work and has been assigned a Nilsson orbital configuration of , while a proposed new isomeric state above it is interpreted as a configuration that decays to via a low-energy, unobserved E2 transition. This is consistent with the systematic trends in neighbouring odd-A nuclei and transition rate calculations. Similar content being viewed by others

Doshi, S.↗
DOE OSTI2025

CUPID, the Cuore upgrade with particle identification

CUPID, the CUORE Upgrade with Particle Identification, is a next-generation experiment to search for neutrinoless double beta decay (0 νββ ) and other rare events using enriched Li 2 100 MoO 4 scintillating bolometers. It will be hosted by the CUORE cryostat located at the Laboratori Nazionali del Gran Sasso in Italy. The main physics goal of CUPID is to search for 0 νββ of 100 Mo with a discovery sensitivity covering the full neutrino mass regime in the inverted ordering scenario, as well as the portion of the normal ordering regime with lightest neutrino mass larger than 10 meV. With a conservative background index of 10 −4 cts/(keV·kg·yr), 240 kg isotope mass, 5 keV FWHM energy resolution at 3 MeV and 10 live-years of data taking, CUPID will have a 90% C.L. half-life exclusion sensitivity of 1.8 · 10 27 yr, corresponding to an effective Majorana neutrino mass ( m ββ ) sensitivity of 9–15 meV, and a 3σ discovery sensitivity of 1 · 10 27 yr, corresponding to an m ββ range of 12–21 meV.

Alfonso, K. [Virginia Polytechnic Institute and St↗
DOE OSTI2025

The XLZD Design Book: towards the next-generation liquid xenon observatory for dark matter and neutrino physics

This report describes the experimental strategy and technologies for XLZD, the next-generation xenon observatory sensitive to dark matter and neutrino physics. In the baseline design, the detector will have an active liquid xenon target of 60 tonnes, which could be increased to 80 tonnes if the market conditions for xenon are favorable. It is based on the mature liquid xenon time projection chamber technology used in current-generation experiments, LZ and XENONnT. The report discusses the baseline design and opportunities for further optimization of the individual detector components. The experiment envisaged here has the capability to explore parameter space for Weakly Interacting Massive Particle (WIMP) dark matter down to the neutrino fog, with a 3σ evidence potential for WIMP-nucleon cross sections as low as 3 x 10 –49 cm 2 (at 40 GeV/c 2 WIMP mass). The observatory will also have leading sensitivity to a wide range of alternative dark matter models. It is projected to have a 3σ observation potential of neutrinoless double beta decay of 136 Xe at a half-life of up to 5.7 x 10 27 years. Additionally, it is sensitive to astrophysical neutrinos from the sun and galactic supernovae.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Establishing Pb-203 production from electrodeposited Tl targets at Brookhaven National Laboratory

Background: Promising developments in Pb-212 radiopharmaceutical therapies have increased demand for Pb-203 diagnostic agents. Building on previous work from various isotope production facilities, this study optimized Pb-203 production from electrodeposited Tl targets at Brookhaven National Laboratory (BNL). The additional supply of Pb-203 may help meet growing preclinical and clinical demands. Results: Two Tl targets were irradiated at the Brookhaven Linac Isotope Producer facility with 30 ± 1 MeV protons, measured using previously published cross section data. Distribution coefficients for Pb Resin in acetate media were investigated for both Na + and K + cations, where potassium acetate was ~ 4 times more effective at stripping Pb from the Pb Resin. The Tl electrodeposition was optimized to deposit 350 mg of Tl (~ 60 mg/cm 2 ) on Au backing in under 6 h. The proposed separation process was completed in < 1.5 h and achieved > 98% and 92 ± 3% recovery of Tl and Pb, respectively, with an overall Tl-Pb separation factor of 6 × 10 5 . The experimentally measured half-life of Pb-203 was 52.4 ± 0.7 h, agreeing with 51.93 ± 0.02 h reported by the National Nuclear Data Center. The radioisotopic purity of the Pb fraction at 24 h post end of bombardment (EOB) from a 24 h irradiation was 66% Pb-203, 28% Pb-201, and 6% Pb-200. Following chemical separation, the Pb-203 produced in this work (21 MBq Pb-203 EOB) achieved apparent molar activities of 10 ± 5 and 0.9 ± 0.5 GBq/µmol for [ 203 Pb]Pb-DOTAM and [ 203 Pb]Pb-DO3A, respectively, decay corrected to EOB. Data derived from this work suggests BNL can produce > 10’s GBq Pb-203 with > 99% radiochemical and radioisotopic purity from Tl-205 for worldwide distribution. Conclusions: The production and separation of Pb-203 from natural Tl target material was successfully demonstrated at BNL. Existing methods were adapted and optimized for the facilities at BNL. Results from this work will guide future large-scale Pb-203 production opportunities at BNL for clinical applications.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2026

Neutrinoless Double Beta Decay of 136 Xe and Related Nuclear Structure Studies (Final Scientific Report)

The search for neutrinoless double-beta decay (0nbb) explores new physics by directly probing the unknown mass scale and possible Majorana nature of the neutrino. The nEXO experiment, one of the two leading proposed ton-scale projects in the US, has a projected sensitivity to the 136 Xe 0nbb half-life of 10 28 years. The interpretation of possible signals in this next generation of experiments would be complicated by significant variations in theoretical calculations of the nuclear matrix elements (NMEs) of the decay, and nuclear structure measurements testing those theories can help address that uncertainty. We have 136 Xe(p,n) 136 Cs reaction at TUNL to deduce the level-scheme of states in 136 Cs through which the lowest-lying 1+ state decays. We find that over 99% of such decays will proceed through at least one isomeric state with a lifetime of order 100ns, which would enable large xenon detectors to employ a delayed-coincidence technique to search for charge-exchange processes including solar neutrino interactions. We have carried out measurements at TUNL of the 134 Xe( 3 He,n) 136 Ba and 136 Xe( 3 He,n) 138 Ba reactions to low-lying 0 + states in the residuals to probe the BCS assumption for QRPA NME calculations for the initial and final nuclei in 136 Xe 0nbb. While the analyses of these reactions is not yet complete and is ongoing, our initial results indicate tension with the BCS assumption. We have assembled a thermosyphon cooling R&D system for nEXO which has demonstrated up to 500 W of cooling in vacuum. We have developed a simple thermosyphon cooling simulation for nEXO and planned laboratory tests with the R&D system to benchmark it.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗