Development of a simple prognostic method for SDD in neutron spectroscopy for steady-state fusion reactors

Neutron spin echo (NSE) spectroscopy provides unique access to microscopic dynamics, but its application is often constrained by low neutron flux, long acquisition times, and significant noise. We present a Bayesian inference approach based on Gaussian process regression (GPR) to reconstruct high-quality spin echo signals from sparse and noisy data by exploiting correlations in reciprocal space. Benchmarks on synthetic datasets and validation with experimental NSE measurements of dendrimers show that GPR suppresses noise, interpolates missing intensity values, and accommodates irregular observations. The method improves accuracy, shortens acquisition times, and enables high-throughput and real-time studies. Beyond NSE, the framework is broadly applicable to other low signal-to-noise ratio scattering techniques, thereby extending the scope of neutron spectroscopy.

Abstract Silicon carbide (SiC)-based detectors offer exceptional radiation hardness and thermal stability, making them suitable for neutron spectroscopy in fusion reactor environments, which are characterized by high temperatures and intense neutron fluxes. In this study we demonstrate a 250 µm-thick 4 H-SiC p–n junction detector that maintains stable deuterium–tritium neutron detection performance across the full temperature range from 25 °C to 500 °C, thereby overcoming the limitations commonly encountered with diamond-based detectors. These results highlight the potential of thick SiC detectors for monitoring neutron flux and performing neutron spectroscopy in harsh environments, such as the breeding blanket of fusion reactors.

The role of chlorine as a neutron poison and as a seed for producing radioactive waste in nuclear systems has driven a renewed interest to improve its nuclear data uncertainties. Additionally, basic and applied science programs that use CLYC (Cs_2LiYCl_6:Ce) detectors for neutron spectroscopy and monitoring are also very sensitive to any change in chlorine nuclear data for simulations of the detector response. In this work, sensitivities relevant for these different applications are addressed through simulations of the efficiency of CLYC detectors in a fast fission spectrum when applying new chlorine nuclear data as input. These simulations are validated by an experimental measurement using CLYC detectors coupled to an ionization chamber loaded with a ^{252}Cf spontaneous fission source. The results are then used to obtain the first reliable direct measurement of the ^{35}Cl(n,p_0) and summed ^{35}Cl(n,p+n,alpha) fission spectrum average cross sections, found to be 54.7(32) and 105.0(98) mb, respectively. The results are within uncertainty of calculated fission spectrum averaged cross sections based on recently re-evaluated chlorine nuclear data, which confirm recent impact studies performed for the Molten Chloride Reactor Experiment. Meanwhile, there currently exists only one published criticality benchmark experiment that is sufficiently sensitive to chlorine nuclear data. Discrepancies are found with this set of criticality safety benchmarks, which are more sensitive to thermal and epithermal neutron energies than the energies, above 100 keV, tested in this current work. Hence, there is still a need to re-evaluate the chlorine nuclear data at lower energies to assess these discrepancies. Interpretation of the data from future “faster” criticality benchmarks, which are needed for next-gen fast reactor designs, benefit from the improved constraints on the chlorine nuclear data validated in this work.

Differences in water and biopolymer dynamics in Australian native fruits and the connection with drought-tolerance markers.

Growth and characterization of SrCl2 crystal for fast neutron spectroscopy

Boric acid (hbox {H}_3hbox {BO}_3, BA), due to its neutron absorption and scattering properties, is used in nuclear medicine and nuclear engineering either as an absorber of thermal neutrons or a moderator of epithermal ones. BA was one of the earliest boron carriers historically evaluated for boron neutron capture therapy (BNCT). Recent advances in neutron spectroscopy and imaging, isotope labelling, and ab initio simulation have renewed interest in BA as a model system for pilot studies. Also in terms of BNCT treatment, BA emerges again as an efficient boron compound in the case of selected tumour types. Nuclear quantum dynamics and nuclear quantum effects, such as zero-point energy (ZPE), significantly influence the structure and vibrational properties of BA, and consequently, via Doppler-broadening, alter the way it scatters and absorbs neutrons. In this work, we systematically characterise the nuclear dynamics of boric acid in an isotope-resolved manner across a broad energy range using VESUVIO, a thermal-to-epithermal neutron station at the ISIS facility. We validate a series of thermodynamic and neutron observables against comprehensive ab initio calculations, providing direct insight into isotope-dependent neutron scattering and absorption in BA. Moreover, we establish limits of detection and quantification of boron and boric acid by concurrently employing neutron Compton scattering, the incident neutron energy-dependent transmission and prompt-gamma activation analysis.

Accurate reconstruction of neutron spectra is essential for fissile material identification and nuclear safeguard applications. However, most existing studies only reconstructed neutron spectrum above 1–2 MeV, leaving the detector response in low energy region poorly constrained. This study introduces a unified experimental-simulation framework for high-fidelity spectrum unfolding in EJ-301 liquid scintillators. Detailed Geant4 Monte Carlo simulations were performed to model energy deposition and light-output processes for both gamma rays and neutrons, generating ideal response functions. To reproduce real detector behavior, energy-resolution parameters were experimentally calibrated using Compton-edge measurements from 137Cs and 22Na sources for 1-inch and 2-inch detectors. Validated by accurate reconstruction of 22Na gamma spectra, the calibrated response matrices were then applied in iterative unfolding algorithms(GRAVEL and MLEM) to reconstruct the neutron spectrum of a 252Cf source. The proposed approach achieves a lower energy threshold of 0.35 MeV and maintains an average deviation below 4.28%, with the best agreement of 1.42% from ISO 8529-1 reference data. The 2-inch detector demonstrated higher efficiency and resolution. This experimentally validated framework bridges the gap between ideal simulations and practical detector performance, providing a robust pathway for precise neutron spectroscopy and quantitative nuclear safeguards verification.

In most condensed-matter systems, local and collective excitations remain decoupled due to their distinct energy scales. Here, we identify the coupled local-collective excitations in the triangular antiferromagnet NaErSe_{2}, by combining neutron spectroscopy with a total angular momentum modeling. The low-lying crystalline electric field (CEF) doublets include a dipolar Γ_{4} ground state forming a stripe-x order and a Γ_{5,6} excited state with dipole-octupole character. High-resolution spectra reveal emergent symmetry-selected dispersions where magnon branches from the ground state are replicated on higher Γ_{4} levels but couple with the Γ_{5,6} levels to form a distinct multipolar band. An applied magnetic field reconstructs the CEF wave functions and polarizes the system into a multipolar ferromagnet, further reshaping the spectra. The study demonstrates the emergent coupling of local and collective excitations driven by strong spin-orbit coupling and establishes NaErSe_{2} as a platform for field-tunable multipolar excitations in frustrated magnets.

Diamond detector with novel contacts for neutron spectroscopy

Abstract Single crystal spinel CoFe 2 O 4 exhibits the largest room‐temperature saturation magnetostriction among non‐rare‐earth compounds and a high Curie temperature ( K), properties that are critical to a wide range of industrial and medical applications. Neutron spectroscopy reveals a large band splitting (∼60 meV) between two ferrimagnetic magnon branches, which is driven by site mixing between Co 2+ and Fe 3+ cations, and a significantly weaker magnetocrystalline anisotropy (∼3 meV). Central to this behavior is the competition between vast mismatched molecular fields on the tetrahedral A ‐site and octahedral B ‐site sublattices and the single‐ion anisotropy on the B ‐site. This creates a strong, energetic anisotropy that locks the magnetic moment within each structural domain in place. As a result of these differing energy scales, switching structural domains is energetically favored over a global spin reorientation under applied magnetic fields, and this is what amplifies the magnetostrictive nature of CoFe 2 O 4 .

CuGeO 3 has long been studied as a prototypical example of the spin-Peierls transition in a S = 1 / 2 Heisenberg chain. Despite intensive investigation of this quasi-one-dimensional material, systematic measurements and calculations of the phonon excitations in the dimerized phase have not to date been possible, leaving certain aspects of the spin-Peierls phenomenon unresolved. We perform state-of-the-art density functional theory (DFT) calculations to compute the electronic structure and phonon dynamics in the low-temperature dimerized phase. We also perform high-resolution neutron spectroscopy to measure the full phonon spectrum over multiple Brillouin zones. We find excellent agreement between our numerical and experimental results that extend to all measurement temperatures. Notable features of our phonon spectra include a number of steeply dispersive modes, nonmonotonic dispersion features, and specific phonon anticrossings, which we relate to the mode eigenvectors. By calculating the magnetic interactions within DFT and studying the effects of different phonon modes on the superexchange paths, we discuss the possibility of observing spin-phonon hybridization effects in experiments performed both in and out of equilibrium.

Neutron spectrometry in space and aviation with a compact scintillator-based detector.

Investigation of the light output properties of organic scintillators in a neutron-scatter TOF spectrometer for improved fast neutron spectroscopy

Abstract The fast-ion distribution function in fusion plasmas can only be measured indirectly by solving an ill-posed inverse problem. The inversion being ill-posed necessitates regularisation of the problem to ensure that the reconstruction of the fast-ion distribution function depends smoothly on the measurements obtained by fast-ion diagnostics. In turn, the resulting reconstruction depends on the choice of regularisation, and it is therefore beneficial to choose a physics-informed prior as regularisation scheme. In this work, we reconstruct the high-energy tail in the MeV-range of the fast-deuterium distribution in JET discharges heated by waves in the ion cyclotron range of frequencies (ICRF) using neutron and gamma-ray emission spectroscopy. We do this by applying a physics-informed prior based on collision physics and a newly formulated ICRF-physics prior, and we compare these results with numerical simulations and inversions based on a standard Tikhonov regularisation scheme. Our findings suggest that the physics-informed regularisation scheme including the ICRF prior improves the reconstructions compared with standard Tikhonov regularisation. Finally, it is shown that constraining the reconstruction to have negative gradients in the directions of phase space dictated by ICRF physics results in a reconstruction that well resembles expectations based on ICRF physics theory and numerical simulations.

The “phonon-glass electron-crystal” is an infamously challenging thermoelectric material design principle due to the interconnectedness of thermal and electronic transport in materials. Here, the incorporation of ∼5-nm particles of diamond—a phonon crystal—into the thermoelectric matrix of SnTe is explored as a route toward low lattice thermal conductivity. This counterintuitive strategy works because the large acoustic property mismatch at the SnTe–diamond interface blocks thermal transport. Between 300 and 773 K, SnTe with 1.0 vol. % nanodiamond inclusion exhibits the lowest average and absolute lattice thermal conductivities of any reported SnTe material in this temperature range. The ultra-low lattice thermal conductivity of the nanocomposites is investigated in the two-channel framework—recently advanced in the context of glassy and disordered materials—whereby heat is transported by propagating and non-propagating phonons termed propagons and diffusons, respectively. Above ∼650 K, calculations demonstrate the breakdown of the phonon gas (propagon-only) model for describing the nanocomposite conductivity. At ∼773 K, conductivity reaches the glassy limit where thermal transport is mediated by diffusons. Neutron spectroscopy reveals that with the increase in temperature, phonon modes in SnTe broaden and overlap in energy. We propose that linewidth broadening from nanodiamond-induced scattering and Umklapp processes promotes coupling and wave-like tunneling between overlapping modes, thereby enhancing diffuson-mediated transport at the expense of propagon transport. This progression toward diffuson-dominated conduction represents a novel transport paradigm in primarily crystalline nanocomposites.

A fundamental feature of the antibody structure is the flexible linker between the 3 fragments that allows great flexibility and simultaneous binding to epitopes of antigens and receptors. Combining dynamic light scattering, neutron spin-echo spectroscopy and PFG-NMR we determine characteristic internal fragment dynamics on top of translational and rotational diffusion under crowding conditions. Short-time and long-time translational diffusion show an effective hard sphere like behavior within a colloidal picture. Internal fragment motions are characterized as “attack” and “search” motions complemented by rotational fragment motions. We find that the “attack” motions exposing the binding domain are highly preserved from low to physiologically relevant concentrations and higher, while “search” motions and overall rotational diffusion are suppressed under crowding conditions. Hydrodynamic interactions change the friction between fragments determining relaxation times while interparticle interactions influence the strength of the entropic spring between fragments. The strategic redesign of the linker region to facilitate “attack” motions and fragment rotation has the potential to enhance the therapeutic efficacy of mAbs.

Abstract 7CLYC scintillators have shown excellent performances for fast neutron spectroscopy, thanks to good energy resolution and superb pulse shape discrimination. In this work, a 7CLYC detector has been studied and characterised with monoenergetic neutrons at metrology laboratories. Results of application in a more complex neutron field are presented and discussed.

Mordenite ((Ca,Na2,K2)Al2Si10O24·7H2O) is a natural and synthetic nanoporous zeolite containing several channels of different sizes in its structure. Because of this, its structure provides an important opportunity to study the relationship between confined and ultraconfined water as these channels have sizes between those typical of these water environments. In this study, the properties of water molecules in these environments were analyzed using inelastic and quasielastic neutron spectroscopy of a natural mordenite. The quasielastic spectra showed the presence of nonfreezing, mobile water molecules through the entire temperature range of the measurements, but very little anisotropy of the dynamics measured along and perpendicular to the channels. Faster and slower quasi-elastic neutron scattering (QENS) components may be consistent with the presence of two separate classes of water molecules in mordenite. Inelastic neutron spectroscopy also found no evidence of directional anisotropy. The strong intensity characteristic of neutron recoil on protons from highly mobile water molecules at low temperature (5 K), along with a significant shift of water librational band to lower energies and the O-H stretching modes to high energies, indicate that the hydrogen bonds acting on these water molecules in mordenite resemble those in liquid water rather than ice.

Neutron spectroscopy with LaCl3(Ce)-based detector on EAST tokamak