Atomic Nuclei Research Articles

Simulation and validation studies of a large drift tube muon tracker.

Cosmic ray muons are massive, charged particles created from high energy cosmic rays colliding with atomic nuclei in Earth's atmosphere. Because of their high momenta and weak interaction, these muons can penetrate through large thicknesses of dense material before being absorbed, making them ideal for nondestructive imaging of objects composed of high-Z elements. A Giant Muon Tracker with two horizontal 8 × 6 in.2 and two vertical 6 × 6 in.2 modules of drift tubes was used to measure muon tracks passing through samples placed inside the detector volume. The experimental results were used to validate a Monte Carlo simulation of the Giant Muon Tracker. The imaging results of simulated samples were reconstructed and compared with those from the experiment, which showed excellent agreement.

Overview of Fragment Separator Superconducting Magnets in the Facility for Rare Isotope Beams

In 2022, the Facility for Rare Isotope Beams (FRIB) has been established as one of the world-class user facilities for the study of physics of atomic nuclei. The key feature is to provide a variety of nuclei with an energy of 200 MeV per nucleon with a beam power up to 400 kW in the FRIB driver linear accelerator (linac). The linac driven beam experiences a series of the FRIB fragment separator, consisting of the hot-cell target hall, vertical pre-separator, and A1900 fragment separator, which eventually allows a successful delivery of the final rare isotope of interest into the experimental vaults. The superconducting magnet commissioning with heavy ion beams has been progressed by the completion of each area sequentially, and finally the first rare isotope of selenium-84 was successfully produced with the FRIB target using a krypton-86 primary beam, demonstrating FRIB's capability for scientific discovery. This paper presents the FRIB superconducting magnet scope, series fabrication and installation, and the energization at the FRIB premises. The discussion deals with the major test results, and also suggests the significance of advanced technology development for the FRIB next-generation superconducting magnet.

Soliton solutions of the equations of hydrodynamics in describing collisions and oscillations of atomic nuclei

The hydrodynamic approach was used to find an analytical solution of the hydrodynamic equations in the soliton approximation for layer collisions in the one- and two-dimensional cases. The compression stage, the decompression stage, and the expansion stage are considered within the framework of a single formula for layers with energies on the order of ten MeV per nucleon. Our generalization to the two-dimensional case leads to the idea of the formation of a rarefied bubble region at the stage of expansion. The approach can be used in other fields for calculations of the nonlinear dynamics of oscillations of complex systems.

Soliton Solutions to Hydrodynamic Equations When Describing Collisions and Oscillations of Atomic Nuclei

Soliton Solutions to Hydrodynamic Equations When Describing Collisions and Oscillations of Atomic Nuclei

A study on nuclear binding energy and beta decay energy using deep neural networks

The Artificial Neural Network (ANN) is one of the innovative methods for predicting the structural and dynamic properties of atomic nuclei. In this work, we employed machine learning based on the Deep Neural Network (DNN) technique to find the ground state binding energy and beta decay energy of various nuclei. 3560 experimental nuclear data sets have been used for training and validating the DNN model. Neutron number (N), proton number (Z), the pairing term (δ), a magic number greater than or equal to N and Z, asymmetry factor (a) and promiscuity factor (P) are used as input parameters. The Rectified Linear Unit (ReLU) function and Mean Absolute Error (MAE) are used as activation and Loss functions for the training process. We perform the predictions of ground state binding energy per nucleon and beta decay energies in Zinc and Promethium isotopes using the DNN model, which is in good agreement with experimental results.

New local magic nucleus <sup>146</sup>Gd

Recently, the existence of a special class of atomic nuclei, local magic nuclei, has been discovered. In the present paper, evidence for the existence of a new local magic nucleus, 146Gd, is presented on the base of experimental data. This nucleus has a magic pair of nucleons (N, Z) = (82, 64). The shell evolution scheme leading to this phenomenon was obtained. It is shown that the tensor proton-neutron force plays a crucial role in this evolution.

Reflective Thinking Profile of Physics Teacher Prospective Students through Nuclear Physics Learning using Virtual Laboratory

Virtual Laboratory is a platform that helps students carry out practicum-based learning both independently and in groups. Nuclear physics is an abstract concept that discusses atomic nuclei, atomic nuclei decay, radioactivity which allows in practice to use virtual. The purpose of this study was to determine the level of students' reflective thinking skills after using the virtual lab in the nuclear physics course. The method used is descriptive quantitative. The data collection technique used a modified Kember reflective questionnaire with 24 statement items consisting of aspects of habitual action, understanding, reflection, and critical reflection. The research subjects were 15 prospective physics teacher students. The results showed that the level of reflective ability: habitual action (72.7%), understanding (89.3%), reflection 76.9% and critical reflection (67.87%) means that all levels are in the high category. These results explain that the profile of students' reflective thinking abilities is in the high category after learning nuclear physics using a virtual laboratory.

Nuclear shell-model simulation in digital quantum computers

The nuclear shell model is one of the prime many-body methods to study the structure of atomic nuclei, but it is hampered by an exponential scaling on the basis size as the number of particles increases. We present a shell-model quantum circuit design strategy to find nuclear ground states by exploiting an adaptive variational quantum eigensolver algorithm. Our circuit implementation is in excellent agreement with classical shell-model simulations for a dozen of light and medium-mass nuclei, including neon and calcium isotopes. We quantify the circuit depth, width and number of gates to encode realistic shell-model wavefunctions. Our strategy also addresses explicitly energy measurements and the required number of circuits to perform them. Our simulated circuits approach the benchmark results exponentially with a polynomial scaling in quantum resources for each nucleus. This work paves the way for quantum computing shell-model studies across the nuclear chart and our quantum resource quantification may be used in configuration-interaction calculations of other fermionic systems.

Prolate-shape dominance in atomic nuclei within the deformed relativistic Hartree-Bogoliubov theory in continuum

Prolate-shape dominance in atomic nuclei within the deformed relativistic Hartree-Bogoliubov theory in continuum

Bayesian averaging for ground state masses of atomic nuclei in a Machine Learning approach

We present global predictions of the ground state mass of atomic nuclei based on a novel Machine Learning algorithm. We combine precision nuclear experimental measurements together with theoretical predictions of unmeasured nuclei. This hybrid data set is used to train a probabilistic neural network. In addition to training on this data, a physics-based loss function is employed to help refine the solutions. The resultant Bayesian averaged predictions have excellent performance compared to the testing set and come with well-quantified uncertainties which are critical for contemporary scientific applications. We assess extrapolations of the model’s predictions and estimate the growth of uncertainties in the region far from measurements.

New method for level-lifetime measurements with thick scintillators

Level lifetimes provide key insight into the structure of atomic nuclei and serve as stringent tests of theoretical descriptions. Though several methods for determining level lifetimes exist for both reaction measurements and decay studies, here the focus is on techniques involving the direct measurement of time differences between population and subsequent depopulation of excited states. The techniques presented herein are broadly applicable across multiple timing ranges, but the approach is specifically described for the βγ timing method. A multi-step, amplitude-dependent time walk correction and timing resolution corrections were employed to address the data analysis complications that arise from using thick scintillators for electron detection. Subsequently, a new Monte Carlo method utilizing measured detector responses obtained from the data, coupled with chi-square minimization, is presented for extracting excited state lifetimes ≳ 100 picoseconds. The framework of this Monte Carlo method is developed for the decay of a state in 68Zn with a known 1.6 ps half life, which is considered prompt given the detection sensitivity of the technique, and then benchmarked using two other excited states in neutron-rich Ni isotopes with 120(34) ps and 1.05(3) ns half lives. Using this new method which takes into account the thick scintillator used, these same half lives were measured to be 135(10) ps and 1.04(24) ns, respectively. The overall good agreement demonstrates the validity of the technique.

Impact of nuclear structure from shell model calculations on nuclear responses to WIMP elastic scattering for $^{19}$F and $^{nat}$Xe targets

Non-relativistic effective field theory (NREFT) is one approach used for describing the interaction of WIMPs with ordinary matter. Among other factors, these interactions are expected to be affected by the structure of the atomic nuclei in the target. The sensitivity of the nuclear response components of the WIMP-nucleus scattering amplitude is investigated using shell model calculations for ^{19}19F and ^{nat}natXe. Resulting integrated nuclear response values are shown to be sensitive to some specifics of the nuclear structure calculations.

Bifurcation and fission in the liquid drop model: A phase-field approach

The liquid drop model, originally used to model atomic nuclei, describes the competition between surface tension and Coulomb force. To help understand how a ball loses stability and becomes prone to fission, we calculate the minimum energy path of the fission process and study the bifurcation branch conjectured by Bohr and Wheeler. We then present the two-dimensional analog for comparison. Our study is conducted with the help of numerical simulations via a phase-field approach.

Observation of high-energy neutrinos from the Galactic plane.

The origin of high-energy cosmic rays, atomic nuclei that continuously impact Earth's atmosphere, is unknown. Because of deflection by interstellar magnetic fields, cosmic rays produced within the Milky Way arrive at Earth from random directions. However, cosmic rays interact with matter near their sources and during propagation, which produces high-energy neutrinos. We searched for neutrino emission using machine learning techniques applied to 10 years of data from the IceCube Neutrino Observatory. By comparing diffuse emission models to a background-only hypothesis, we identified neutrino emission from the Galactic plane at the 4.5σ level of significance. The signal is consistent with diffuse emission of neutrinos from the Milky Way but could also arise from a population of unresolved point sources.

Interactive Multimedia Based on Cognitive Conflict to Improve Understanding of Student Concepts in Atomic Nucleus Materials

Interactive Multimedia Based on Cognitive Conflict to Improve Understanding of Student Concepts in Atomic Nucleus Materials

Structure Determination and Refinement of Paramagnetic Materials by Solid-State NMR.

Paramagnetism in solid-state materials has long been considered an additional challenge for structural investigations by using solid-state nuclear magnetic resonance spectroscopy (ssNMR). The strong interactions between unpaired electrons and the surrounding atomic nuclei, on the one hand, are complex to describe, and on the other hand can cause fast decaying signals and extremely broad resonances. However, significant progress has been made over the recent years in developing both theoretical models to understand and calculate the frequency shifts due to paramagnetism and also more sophisticated experimental protocols for obtaining high-resolution ssNMR spectra. While the field is continuously moving forward, to date, the combination of state-of-the-art numerical and experimental techniques enables us to obtain high-quality data for a variety of systems. This involves the determination of several ssNMR parameters that represent different contributions to the frequency shift in paramagnetic solids. These contributions encode structural information on the studied material on various length scales, ranging from crystal morphologies, to the mid- and long-range order, down to the local atomic bonding environment. In this perspective, the different ssNMR parameters characteristic for paramagnetic materials are discussed with a focus on their interpretation in terms of structure. This includes a summary of studies that have explored the information content of these ssNMR parameters, mostly to complement experimental data from other methods, e.g., X-ray diffraction. The presented overview aims to demonstrate how far ssNMR has hitherto been able to determine and refine the structures of materials and to discuss where it currently falls short of its full potential. We attempt to highlight how much further ssNMR can be pushed to determine and refine structure to deliver a comprehensive structural characterization of paramagnetic materials comparable to what is to date achieved by the combined effort of electron microscopy, diffraction, and spectroscopy.

A comprehensive study on intrinsic alpha corpuscular radiation damage in monazite crystals using picometer-scale imaging, coupled with SCXRD and Raman spectroscopy

We have investigated monazite crystals, known to experience lattice distortions due to alpha particle emission from their atomic nuclei. Our aim in this investigation is to study the complex relationship between the lattice parameters and Raman spectra of monazite crystals. Through this study, we seek to understand the interdependency between these physical parameters and their influence on one another for an improved understanding of radiation-induced damage in these crystals. In addition to this, we also attempted to establish a correlation between these properties and their picometer-scale images to gain a deeper understanding of the structural changes that occur at the atomic scale. We conducted our study on four monazite samples withstanding intrinsic alpha decay radiation, denoted as M1, M2, M3, and M4, with crystal unit cell volume ranging from 299.961 Å3 to 301.96 Å3. Our Pearson statistical analysis revealed a correlation R2 (0.96) between the SCXRD-derived Ce–P Distance of monazite and the FWHM of PO4 band active mode in Raman spectra. This indicated lattice distortions due to alpha decay radiation impacting the Raman spectra. While Raman PO4 band broadening can be a consequence of impurities, dopants, and radiation damage, HRTEM scrutiny of the samples at picometer scales revealed the presence of point defects, plane rotation, and lattice distortions within the samples, suggesting the impact of alpha decay on the crystal lattice. HRTEM analysis has added additional confirmation that the major contribution to PO4 band broadening is due to alpha radiation damage in these samples. Through our study, we conclude a multiple-approach correlation is necessary to accurately study radiation damage dynamics at atomic scales.

γ-photons and high-energy electrons produced by neutron irradiation in nuclear materials

Neutrons interacting with atomic nuclei in most of the materials included in the current fusion reactor designs—notably tungsten, ferritic and stainless steels, copper alloys—generate a γ-photon flux that is comparable in magnitude and energy with that of the neutrons, and which in turn generates an intense flux of high-energy electrons in the materials themselves. The occurrence of these γ- and electron fluxes has implications, among others, for the mobility of crystal defects in the materials, for the stability of the plasma, and for the internal heating of reactor components. While a highly spatially resolved numerical calculation of neutron, photon, and electron fluxes on the reactor scale is computationally unfeasible, it is possible to provide estimates based on solutions of Boltzmann's transport equation in a stationary and homogeneous material. Within their limits of validity, these estimates are robust and straightforward and they enable studying photon and electron generation in various materials, under different fission and fusion irradiation conditions and at various locations inside a reactor. We show that the irradiation environment provided by the IFMIF irradiation facility is similar to the expected fusion power plant conditions both in terms of the energy and intensity of photons and electrons generated by the neutrons in tungsten and steels.

Silicon tracker for cluster-knockout reactions at intermediate energies

The cluster-knockout reaction project, ONOKORO, has been launched to elucidate the formation mechanism of clusters in atomic nuclei. For the inverse-kinetics cluster-knockout reaction experiments, a new detector array is under development to measure energies and angles of light ions emitted in the reactions. The silicon tracker tracks the particles with good angular and energy-loss resolutions. A performance test of the silicon strip detectors with a thickness of 100μm and a strip width of 100μm was performed using prototype silicon detectors. The mono-energetic proton and α-particle beams were irradiated on the silicon detectors. The energy-loss spectra in silicon detectors showed a good signal-to-noise ratio. The threshold level for signal detection is seven sigma of noise level. Their dynamic ranges were optimized wide enough to detect charge number Z= 1 and Z= 2 ions emitted in the cluster-knockout reactions.

Photonuclear legacy of the research group headed by B. S. Ishkhanov

A review of those photonuclear studies that were carried out at Skobeltsyn Institute of Nuclear Physics of M.V. Lomonosov Moscow State University (NIIYaF) in the Department of Electromagnetic Processes and Interactions of Atomic Nuclei (DEPIAN) in a 60-year period (1960–2020) by a group of researchers headed by Boris S. Ishkhanov is presented.