Nuclear moment studies carried out with spin-precession methods at and after the turn of the millennium are critically assessed. A period of about 30 years is covered, during which much of} the focus of nuclear structure research shifted from high-spin physics to studies of neutron-rich exotic nuclei. The formalism for the extraction of nuclear moments is described. The $β$-nuclear magnetic resonance/nuclear quadrupole resonance ($β$-NMR/NQR), the time-dependent perturbed angular distribution (TDPAD), the transient field, the recoil-in-vacuum (RIV), and the tilted-foils methods for measurements of nuclear magnetic dipole and electric quadrupole moments are described in detail, as well as the requirements for their application in studies of exotic nuclei. The impact of nuclear-moment measurements on the understanding of key topics of nuclear structure research is discussed. {Key results on short-lived states, mainly from transient-field measurements, are reviewed. Included are comparisons with large-basis shell model calculations, discussions on the nature of weakly-collective nuclei, insights into emerging collectivity away from closed shells, and electromagnetic properties of odd-$A$ rotors.} In the field of high-spin physics, research related to high-spin yrast and $\mathrm{K}$ isomers, superdeformation, magnetic, anti-magnetic, and chiral rotation is covered. In neutron-rich exotic nuclei, studies related to the $\mathrm{N=20}$, $\mathrm{N=28}$ and $\mathrm{N=40}$ ``islands of inversion'', the structure of nuclei around $^{68-78}$Ni and $^{132}$Sn, and in the $A \sim 100$ mass region are discussed.

The efficient use of energy resources for scientific research is a challenging and timely topic, in particular for scientific fields that require particle accelerator facilities, such as particle or nuclear physics. Accelerator facilities capable of providing high electron beam currents with minimum emittance to ultra-relativistic energies are needed for the production of intense, MeV-ranged, quasi-monochromatic photon beams for photonuclear research and nuclear photonics applications. This contribution presents a design for such an electron accelerator which is capable of recycling most of the kinetic energy of the ultra-relativistic electrons by beam deceleration after a quasi destruction-free usage, thereby lowering significantly the electrical power consumption footprint of operating the accelerator without compromising beam delivery performance. We provide for the first time a technically quantitative design for a thrice-recirculating, superconducting energy-recovery LINAC (ERL) with individual beam transport focusing primarily on its use as a driver for a source of MeV-ranged photons from a laser-Compton backscattering (LCB) scheme. As a specific example, we choose an ERL design for maximum electron energy of 520 MeV at an electron current of up to 26 mA in continous wave mode at 1.3 GHz. This allows for 0.79 mA average current in a pulsed mode at 39.4 MHz, providing unprecedented spectral densities on the order of 105 γ /(eV s) on target for photon energies around 5 MeV with the aforementioned repetition rate. Our Design concept of an Individually recirculating Compact ERL (DICE) is discussed. Options for its scientific use are sketched.

Nuclear charge radii constitute a physical observable of growing significance across multiple subdisciplines of physics and related fields. Their determination relies on a combination of complementary experimental techniques and advanced theoretical frameworks. Current recommended values are informed by the outcomes of several independent working groups, each employing distinct methodological approaches and evaluation strategies. The present effort is directed toward a more precise and reliable extraction of charge radii, as well as the development of a modern, transparent, and methodologically robust compilation of recommended values.

We present the design, modeling, and experimental validation of a radio-frequency based time-to-position conversion system for keV electrons incorporating a helical deflector operating in the 400-1000 MHz range. The device performs circular deflection of the electrons when driven by a single RF frequency and enables spiral scanning when two phase-locked RF voltages with slightly different frequencies are applied. The superposition of the two phase-locked RF voltages produces an amplitude-beating field whose slowly varying envelope modulates the deflection radius, transforming the circular scan into a controlled spiral on the detector plane. A detailed theoretical model describing the electron dynamics under two phase-locked RF voltages with different frequencies was derived, yielding analytical expressions for the transverse velocity and radius-vector components at the deflector exit. The experimental studies demonstrated good agreement with the model predictions. Spiral scanning will allow measurements with picosecond resolution in a temporal dynamic range 1-2 orders of magnitude larger than the period of the circular scanning.

Vortex photons, carrying intrinsic orbital angular momentum, introduce an additional degree of freedom in photon–nucleus interactions and provide a promising approach to investigate the actinide photofission. In this work, combining the nuclear statistical theory and the formalism of the interaction between nuclei and vortex photons, for the first time we develop a theoretical framework describing vortex γ-ray beams induced fission channel (γvo,f) for both microscopic and macroscopic targets. For several representative actinides (232Th, 235U, 238U, and 239Pu), the (γvo,f) cross sections are calculated. The results show that the multipole excitations of the photofission, reflected by the (γvo,f) cross sections, can be significantly enhanced when specific vortex photon parameters are considered. In general, with the total angular-momentum projection mγ=4, the polar angle θk=71∘, and the impact parameter b=10 fm, the (γvo,f) cross sections are enhanced by factors of  ∼ 3–14 compared to the results of plane-wave photons induced fission. In particular, for 238U, the enhancement reaches  ∼ 12 at Eγ=6 MeV. It is also found that for macroscopic targets, by averaging the impact parameter, the enhancement of the photofission cross section depends primarily on θk and becomes essentially independent of mγ. Furthermore, based on the calculated fission observables for macroscopic targets, we propose a method to diagnose the characteristics of vortex γ photons, of which the vortex parameter θk is extracted from the yield ratio of fission fragment induced by pure plane-wave photon beam and mixed photon beam containing both plane-wave and vortex photons. Further Geant4 simulations are performed to verify the feasibility of this approach. The present work conducts the first study of vortex photons induced fission by providing the theoretical foundation and practical methodology for future photofission experiments and vortex γ photons diagnostics.

Simultaneous, broadband, high-precision direct mass measurements of thermalized exotic nuclides are reported. The FRS Ion Catcher and, in particular, its high-resolution multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) was used to measure neutron-rich nuclides in the element range from barium to europium, produced by the spontaneous fission of 252Cf. Results include the measurement of 64 masses, including 13 masses with no previous direct determination; for four nuclides, a measurement with improved uncertainty is reported. Relative mass uncertainties below 1 x 10-7are routinely achieved. This work shows the first use of a multiple-reflection time-of-flight mass spectrometer to map a larger region of the nuclear chart covering 51 masses measured simultaneously in a single setting. The broadband capability is a design feature of the MR-TOF-MS of the FRS Ion Catcher which enables the large-scale mapping of the mass surface. The obtained data are compared to existing literature values and predictions of mass models and are used to study the shape-phase transition at N = 90. A theoretical study, employing a Hartree-Fock-BCS approach with adjustable pairing strengths, is implemented to examine the evolution of the two-neutron separation energies along this region of the chart of nuclei.

The Mini-electronic Time Projection Chamber (Mini-eTPC) of ELI-NP is a state-of-the-art gaseous target detector whose primary application consists in studying reactions relevant to the field of nuclear astrophysics. A key element toward ensuring the optimal functionality of the Mini-eTPC is its associated Gas Management System (GMS), which allows the gas target to be recirculated through the active volume with a high degree of pressure stability over time and adequate purification to ensure minimal chances of contamination. The configuration and functionality of the GMS components are presented herein in turn, along with the reasoning that led to the specific design choices behind their implementation and the tests that were performed to ensure their optimal functionality. Our results show that the GMS can provide stability levels within +/- 0.01 mbar(a) of the required working pressure over almost 200 hours of continuous operation, meaning that the Mini-eTPC can be confidently used to perform extended astrophysics studies while purifying and recovering the gas target instead of venting it. Looking ahead, we plan to upscale the GMS design to create a separate gas system for serving the larger ELI-TPC that will become a key setup of our facility in the near future.

Neutron-induced reactions are an essential part of the nucleosynthesis process. In the present study, neutron capture cross-sections and reaction rates are systematically studied considering the nuclear structure obtained from microscopic and phenomenological models. In particular, the nuclear level density (NLD) derived from the microscopic Hartree-Fock-Bogoliuboiv plus combinatorial method and the phenomenological Constant Temperature model, and the gamma-ray strength function (gamma SF) determined by the semi-microscopic Gogny D1M interaction plus Quasi Random Phase Approximation and the global empirical Standard Modified Lorentzian are taken into account in the calculation, and the results are compared to the available experimental Maxwellian-averaged cross-sections. It is demonstrated that the experimental data are well reproduced by the nuclear structure models considered here, and the predictive power of these nuclear ingredients is very close. Furthermore, a sensitivity study of neutron capture reaction to the available nuclear ingredients for unstable nuclei, e.g. for Zr-89, is performed, which indicates that the NLD and gamma SF can considerably influence the crosssection and reaction rate. Therefore, we investigate the applicability of the NLD and gamma SF obtained from the analysis of stable nuclei to the calculations of all eight unstable nuclei of which the NLDs are experimentally determined so far. A good agreement of the astrophysical reaction rates predicted by the aforementioned nuclear structure ingredients is found.

Here we report on the measurements of the gamma -ray strength functions and nuclear level densities of 112,114Sn performed for the first time at the 9-MV Tandem accelerator facilities at Horia Hulubei Institute for Physics and Nuclear Engineering using the Oslo method. We extract thermodynamic properties and gross and fine properties of the pygmy dipole resonance for systematic comparison in the chain of Sn isotopes. The results are compared with microscopic models implemented in the TALYS reaction code and the fully microscopic quasiparticlephonon model for the underlying nuclear structure of the dipole strength in 112,114Sn. The quasiparticle-phonon model results show the importance of complex configurations to the low-energy dipole response in the pygmy dipole resonance energy region. The experimental data are further included in the cross section and reaction rate calculations for the (n, gamma ) reaction of the p-process nuclei 112,114Sn showing a significant increase in reaction rates at high temperatures compared to existing nuclear databases.

The first direct mass measurement of Pd-93, the one-proton-decay daughter of the (21+) isomer in Ag-94, has been performed, resulting in a mass excess value of -59 127(35) keV and reducing the mass uncertainty by an order of magnitude. As a consequence, the excitation energies of the presumed parent states of the one-proton This shows that there is an incompatibility in the previously reported decay scheme of the 1p and 2p branches. Three scenarios are discussed, which could resolve this apparent contradiction, and elucidated by performing state-of-the-art shell-model and mean-field calculations. The latter confirm that, based on the reported decay information, the 2p emission cannot be fed from the same (21(+)) isomer as the 1p emission, but indicate that it could originate from a second, structurally different, high-spin state.

We report on a novel design for a HPGe-BGO pair spectrometer with the aim to enhance the performance of existing HPGe detectors for high-energy γ-rays. In addition, the BGO shield as a standalone detector allows for a use with the selective detection of positron annihilation. The compact geometry was optimized to use it with ELIADE, the HPGe array at VEGA (ELI-NP). We present the design, results from two commissioning runs with high-energy γ-rays and an outlook to future applications.

In the period 2022-2025, four experimental campaigns were car­ried out at the 9 MW tandem accelerator of IFIN-HH using the large-volume LaBr3 :Ce and CeBr3 detectors of the ELIGANT-GN array, which were placed in the anti-Compton shields of the ROSPHERE. As a result, a highly efficient spec­trometer, ELIFANT, was assembled for the detection of high-energy gamma rays. In the experiments, nuclear level densities and γ-strength functions were studied, as well as weak γ-ray transitions in light nuclei. In the paper, the per­formance of the spectrometer is described, the goals of the campaigns are sum­marized, and first results are presented, e.g., the γ-ray spectroscopy in 10B and the γ-strength functions in 112,114Sn. The ELIGANT-GN array was also used to study neutron and γ-ray angular and energy correlations in spontaneous fission of 252Cf. First results from these studies are presented, too.

The isospin mixing was deduced in the compound nucleus 72Kr at a low nuclear temperature around 1.3 MeV, from the gamma decay of the giant dipole resonance. The gamma rays from two compound-nucleus reactions were measured: from the 32 S + 40Ca at bombarding energy of 90 MeV characterized by isospin I = 0, and from the 31 P + 40Ca at 82 MeV used as a reference. The ELIFANT array was employed at the Bucharest Tandem Laboratory, consisting of Compton-suppressed scintillator detectors. The statistical-model analysis of the measured spectra provided a mixing parameter of (3.5 +/- 0.8)%. This new point, being at the lowest temperature compared with the few other existing ones, can validate the predictions of the temperature dependence of the isospin mixing. The isospinsymmetry-breaking correction, delta c, used for the Fermi super-allowed transitions was extracted from the present result of the isospin mixing and found to be consistent with beta decay data, theoretical predictions, and previous experimental results.

The vortex photon beam induced nuclear reaction is studied. The interaction formalism of nuclei with vortex photons is developed and incorporated into the statistical reaction model to calculate reaction cross-sections. For 138 nuclei of high nuclear astrophysics and structure interest, the cross-sections of γ-ray emission and neutron production from the decay of the giant resonances (GR) populated by vortex photons, e.g., (γvo,γemit) and (γvo,nprod.), are computed. It is shown that for the (γvo,γemit) and (γvo,nprod.) cross-sections, the GR contribution of an individual L is either enhanced or suppressed depending on the parameters of vortex γ-rays, and the contribution from the GR of a specific L can be identified and deduced. To this end, a novel method to exclusively determine the γ-strength function (γSF) for the GR of a specific L is proposed considering the (γvo,γemit) and (γvo,nprod.) measurements, and the feasibility studies demonstrate that the γSF for the giant quadrupole resonance can be extracted. Furthermore, the astrophysical reaction rates of the vortex photon induced reactions in p-process are investigated. It is indicated that photo-nuclear reactions induced by vortex photons will bring new insights in nuclear physics and astrophysics research.

Fluorine is one of the most interesting elements in nuclear astrophysics. Its abundance can provide important hints to constrain the stellar models since fluorine production and destruction are strictly connected to the physical conditions inside the stars. The F19(p,α)16O reaction is one of the fluorine burning processes and the correction evaluation of its reaction rate is of pivotal importance to evaluate the fluorine abundance. Moreover, the F19(p,α)16O reaction rate can have an impact for the production of calcium in the first-generation of Population III stars. Here, we present the AsFiN collaboration efforts to the study of the F19(p,α)16O reaction by means of direct and indirect measurements. On the direct measurements side, an experimental campaign aimed to the measurement of the F19(p,α0,π)16O reaction is ongoing, taking advantage of the new versatile arrays of silicon strip detectors, LHASA and ELISSA. Moreover, the Trojan Horse Method (THM) was used to determine the F19(p,α0)16O reaction S(E)-factor in the energy range of astrophysical interest (Ecm≈ 0–1 MeV), showing, for the first time, the presence of resonant structures within the astrophysical energy range. THM has been also applied for the study of the F19(p,απ)16O reaction; data analysis is ongoing.

High energy photons, or γ -rays, were among the very first probes used to induce fission. Their significant impact in this field is due to particular properties of the γ -rays, such as the lack of a Coulomb barrier and the low, well-defined angular momentum transfer, but also to the variety of γ -ray sources developed over the years. This variety, going from simple but intense bremsstrahlung beams, through complex virtual photon excitations, to high resolution monochromatic sources of several types, gave rise to extensive photo-fission research programs. The review presents the evolution over more than 80 years of the methodology and instrumentation used in photo-fission experiments. The most important developments in fundamental and applied science are summarized and discussed. The main improvements necessary for the progression of this field into the age of nuclear photonics are outlined.

The Geant4 photonuclear process was benchmarked by comparing it with experimental data to verify the ability of the Geant4 toolkit to simulate the photon-induced reaction on deformed nuclei in the Giant Dipole Resonance (GDR) region. The simulation results are compared with experimental data of the deformed nuclei (153Eu, 160Gd, 165Ho, and 186W) targets in terms of both the average neutron energies and the photonuclear cross-sections. A reasonable agreement can be found between simulations and experimental data for the average neutron energies. However, Geant4 native cross-section models cannot accurately re-generate the measured photonuclear cross-sections of all four studied deformed nuclei. Meanwhile, the Talys-based cross-section model offers a decent agreement with the experimental data. We also used the simulations to re-interpret the experimental average energies for 160Gd.

Nuclear photonics is a emerging field of science which combines research with new generation γ -ray sources based on traditional and laser-based electron accelerators. Here, we discuss isomeric studies carried out with γ -ray beams having either continuous, or quasi-monochromatic photon spectra. In experiments with high-power lasers, intense secondary radiation sources are generated. Such experiments explore isomer population or de-excitation in plasma environments. Laser-accelerated particle beams with high charge also facilitate high-energy nuclear excitations, leading to efficient production of nuclear isomers with higher lying isomeric state (reaching MeV energy level) within very-short time scales. The population of isomeric states is a sensitive diagnostic method for characterization of the laser-driven secondary radiation sources.

. - The high-energy gamma-rays from the GDR decay of 56,60,62Ni* nuclei at finite temperature, produced in the reactions 32,34,36S + 24,26Mg at bombarding energies between 78 , 90 MeV, were measured and analyzed with statistical model using a Monte Carlo approach. It is found that the present analysis gives some evidence on the presence of an extra yield on the tail of the Giant Dipole Resonance which may be attributed to a Pygmy Dipole Resonance in an excited nucleus.

A γ-ray spectroscopic study of 10B is reported. Excited states in 10B were populated in inelastic proton scattering and their γ-decays were measured with the ELIFANT array, a state-of-the-art spectrometer with large volume LaBr3:Ce and CeBr3 detectors placed in anti-Compton shields and having unprecedented efficiency for high-energy γ rays. A few weak transitions were observed in the experiment, namely M3 transition between Jπ, T = 0+1, 1 isobaric analog state to the Jπ, T = 3+1,0 ground state and E2 transition between the Jπ, T = 2+1,0 state and the isobaric analog state. The results are compared to a new set of ab initio no-core shell model calculation using the newest version of the local position-space chiral N3LO nucleon-nucleon interaction, which correctly reproduces the spectrum of the excited states in 10B, a problem of the theory in previous years.