Nuclear Physics Research Articles

Small cross section of the synthesis of darmstadtium in the Ca48+Th232 reaction

The smallness of the cross section of evaporation residues formed in the hot fusion reaction Ca48+Th232 is analyzed by the dinuclear system model (DNS). The capture probability has been calculated by solving the dynamical equations of motion for the relative distance between the centers of mass of the DNS nuclei. Fusion of nuclei is considered as evolution of the DNS to a stable compound nucleus. The fusion probability has a bell-like shape and quasifission is one of reasons causing smallness of the yield of the evaporation residues products. Another reason is the decrease of the fission barrier for the isotopes Dm275–285 related with the shell effects in the neutron structure. The agreement of the theoretical results obtained for the yield of the evaporation residues with the experimental data measured in the Factory of Superheavy Elements of Joint Institute for Nuclear Research is well. Published by the American Physical Society 2024

X-ray and neutron imaging for cultural heritage: the INFN-CHNet experience

This paper reports on the instrumentation and expertise developed within the INFN-CHNet network for X-ray and neutron imaging, which enable non-invasive identification of materials and production processes in the field of cultural heritage. INFN-CHNet is the network of the Italian National Institute of Nuclear Physics specifically dedicated to the development and application of scientific methods and technologies to cultural heritage. This article focuses on portable MA-XRF scanners, often complemented by additional techniques, PIXE imaging on a newly developed portable accelerator, X-ray radiography and tomography, exploited to their full potential also through the use of portable systems, and neutron radiography and tomography, which require large-scale facilities. In many respects, the information obtained from X-ray and neutron-based methods is complementary, facilitating a comprehensive characterisation of materials, structures, and manufacturing techniques.Graphical abstract

Parameter optimisation using Bayesian inference for spallation models

The accuracy and precision of high-energy spallation models are key issues for the design and development of new applications and experiments. We present a method to estimate model parameters and associated uncertainties by leveraging the Bayesian version of the Generalised Least Squares method, which enables us to incorporate prior knowledge on the parameter values. This approach is designed to adjust parameters based on experimental data, accounting for experimental uncertainty information, and providing uncertainties for all adjusted parameters. This approach is designed in order both to improve the accuracy of models through the modification of free parameters of these models, which results in a better reproduction of experimental data, and to estimate the uncertainties of these parameters and, by extension, their impacts on the model output. We aim at demonstrating the Generalised Least Square method can be applied in the case of Monte Carlo models. We present a proof-of-concept for Monte Carlo models in the specific case of nuclear physics with the model combination INCL/ABLA. We discuss the challenges in the application of this method to high-energy spallation models, notably the large runtime and the stochasticity of the models. Our results indicate this framework can also be applied to analogous situations where parameters of a computationally expensive Monte Carlo code should be inferred/improved.

Non-autonomous Volterra series expansion of the Variable Phase Approximation and its application to the nucleon-nucleon inverse scattering problem

Abstract In this paper, the non-linear Volterra series expansion is extended and used to describe certain types of non-autonomous differential equations related to the inverse scattering problem in nuclear physics. The non-autonomous Volterra series expansion lets us determine a dynamic, polynomial approximation of the variable phase approximation (VPA), which is used to determine the phase shifts from nuclear potentials through first-order non-linear differential equations. By using the first-order Volterra expansion, a robust approximation is formulated to the inverse scattering problem for weak potentials and/or high energies. The method is then extended with the help of radial basis function neural networks by applying a nonlinear transformation on the measured phase shifts to be able to model the scattering system with a linear approximation given by the first order Volterra expansion. The method is applied to describe the 1S0 NN potentials in neutron+proton scattering below 200 MeV laboratory kinetic energies, giving physically sensible potentials and below $1\%$ averaged relative error between the re-calculated and the measured phase shifts.

Explicitly Correlated Gaussians with Tensor Pre-factors: Analytic Matrix Elements

We consider a specific form of explicitly correlated Gaussians—with tensor pre-factors—which appear naturally when dealing with certain few-body systems in nuclear and particle physics. We derive analytic matrix elements with these Gaussians—overlap, kinetic energy, and Coulomb potential—to be used in variational calculations of those systems. We also perform a quick test of the derived formulae by applying them to p- and d-waves of the hydrogen atom.

Analysis of 115In(n,γ)116mIn reaction cross-section and covariance for 13.52MeV and 14.54MeV neutron induced energies.

Neutron induced reactions play a vital role in the field of nuclear and particle physics. An effort was made to study the neutron-induced reaction cross-section of 115In(n,γ)116mIn with 197Au(n,γ)198Au as monitor reaction and carried out the reaction for the neutron energies of 13.520±0.005 and 14.54±0.24MeV. The neutrons obtained from the D-T fusion reaction of Purnima neutron generator were used for the activation of the given reaction and the monitor. The covariance analysis and the partial uncertainties due to various attributes were utilised for estimating the uncertainty propagation and hence obtained the correlation for measured reaction cross-sections. The measured reaction cross-sections have been validated with earlier reported data from EXFOR, ENDF data of various libraries, and also theoretically calculated the values of the TALYS-1.9 code.

Contributions of Prof. P. Venkataramaiah to the research on radiation physics and education in India.

Prof. P. Venkataramaiah (P.V.), born on July 08, 1937, has been active in research for the past five decades in several areas of Nuclear Physics and Environmental Sciences. He has visited several Universities and research institutes in various countries such as Japan, Hong Kong, Singapore, France, the UK, Canada and the USA. Apart from research work he has also held many administrative positions and made revolutionary improvements in the education sector of India. Even after retirement, Prof. P.V. has actively involved himself inspiring and encouraging the younger generation at secondary level. As an honour for his untiring dedication even in his eighties, his colleagues and students have written articles about his contributions to research and education. This include contributions from Prof. P.V. himself along with Prof. K.S. Mallesh, Prof. N. Nagaiah, Prof. S.A. Bari, Prof. M. Venkateshwaralu, Shri. M. Vasudev, Dr K. Nagaraja, Mrs. Sreemathi Hariprasad and Dr N. Bhagyalakshmi.

Pulsed-Mode Magnetic Field Measurements with a Single Stretched Wire System

In synchrotrons, accurate knowledge of the magnetic field generated by bending dipole magnets is essential to ensure beam stability. Measurement campaigns are necessary to characterize the field. The choice of the measurement method for such campaigns is determined by the combination of magnet dimensions and operating conditions and typically require a trade-off between accuracy and versatility. The single stretched wire (SSW) is a well-known, polyvalent method to measure the integral field of magnets having a wide range of geometries. It, however, requires steady-state excitation. This work presents a novel implementation of this method called pulsed SSW, which allows the system to measure rapidly time-varying magnetic fields, as is often needed, to save power or gain beam time. We first introduce the measurement principle of the pulsed SSW, followed by a combined strategy to calculate the absolute magnetic field by incorporating the classic DC SSW method. Using a bending magnet from the Proton Synchrotron Booster located at the European Organization for Nuclear Research as a case study, we validate the pulsed SSW method and compare its dynamic measurement capabilities to a fixed induction coil, showing thereby how the coil calibration must be adjusted according to the field level. Finally, we assess the method’s measurement accuracy using the standard SSW as a reference and present an analysis of the primary noise contributors.

Feasibility of probing the NEEC process using storage rings

One of the fundamental processes in nuclear physics is nuclear excitation by electron capture (NEEC). Having been proposed theoretically for almost 50 years, the experimental confirmation of NEEC is still missing, making it imperative to validate this process. In this paper, we propose a new experimental method based on the anti-coincidence principle to search for the long-anticipated NEEC phenomenon, which involve heavy-ion storage rings. Our calculations indicate that the proposed experimental setup, storage ring, have the potential to surmount background noise, particularly Radiative Recombination (RR) and Coulomb Excitation (CE), and offer a high likelihood of discovering the long-awaited NEEC process.

Neutron Skins: Weak Elastic Scattering and Neutron Stars

The recently completed PREX-2 campaign measured the density distribution of neutrons in the lead nucleus as a function of momentum transfer (the form factor), confirmed a relatively large extent of the neutrons beyond the protons in the nucleus (the neutron skin), and provided a precise determination of the density of protons and neutrons at the center of a heavy nucleus. In turn, the measured form factor can be related to various nuclear and neutron star properties. The NICER X-ray telescope has inferred the masses and radii of some X-ray pulsars (neutron stars), although complications arise when determining these quantities independently. Further improvements in NICER have enabled simultaneous mass–radius determinations that had not previously been possible. During the next decade, measurements in astrophysics, gravitational-wave astronomy, and nuclear physics are expected to provide a wealth of more precise data. In this review, we present an overview of the current state of neutron skin measurements and offer insights into prospects for the future.

Nonlinear-optical analogies in nuclear-like soliton reactions: selection rules, nonlinear tunneling and sub-barrier fusion-fission

Abstract The main goal of our article is to reveal unexpected but intriguing analogies arising between optical solitons and nuclear physics, which still remain hidden from us. We consider the main cornerstones of the concept of nonlinear optics of nuclear reactions and the well-dressed repulsive-core solitons. On the base of this model, we reveal the most intriguing properties of the nonlinear tunneling of nucleus-like solitons and the soliton selfinduced sub-barrier transparency effect. We describe novel interesting and stimulating analogies between the interaction of nucleus-like solitons on the repulsive barrier and nuclear sub-barrier reactions. The main finding of our study concerns the conservation of total number of nucleons (or the baryon number) in nuclear-like soliton reactions. We show that inelastic interactions among well-dressed repulsive-core solitons arise only when a “cloud” of “dressing” spectral side-bands appears in the frequency spectra of the solitons. This property of nucleus-like solitons is directly related to the nuclear density distribution described by the dimensionless small shape-squareness parameter. Thus the Fourier spectra of nucleus-like solitons are similar to the nuclear form factors. We show that the nuclear-like reactions between well-dressed solitons are realized by “exchange” between “particle-like” side-bands in their spectra.

Nonlinear-optical analogies in nuclear-like soliton reactions: selection rules, nonlinear tunneling and sub-barrier fusion-fission

Abstract The main goal of our article is to reveal unexpected but intriguing analogies arising between optical solitons and nuclear physics, which still remain hidden from us. We consider the main cornerstones of the concept of nonlinear optics of nuclear reactions and the well-dressed repulsive-core solitons. On the base of this model, we reveal the most intriguing properties of the nonlinear tunneling of nucleus-like solitons and the soliton selfinduced sub-barrier transparency effect. We describe novel interesting and stimulating analogies between the interaction of nucleus-like solitons on the repulsive barrier and nuclear sub-barrier reactions. The main finding of our study concerns the conservation of total number of nucleons (or the baryon number) in nuclear-like soliton reactions. We show that inelastic interactions among well-dressed repulsive-core solitons arise only when a “cloud” of “dressing” spectral side-bands appears in the frequency spectra of the solitons. This property of nucleus-like solitons is directly related to the nuclear density distribution described by the dimensionless small shape-squareness parameter. Thus the Fourier spectra of nucleus-like solitons are similar to the nuclear form factors. We show that the nuclear-like reactions between well-dressed solitons are realized by “exchange” between “particle-like” side-bands in their spectra.

Machine Learning in the Problem of Extrapolating Variational Calculations in Nuclear Physics

A modified machine learning method is proposed, utilizing an ensemble of artificial neural networks for the extrapolation of energies obtained in variational calculations, specifically in the No-core Shell Model (NCSM), to the case of the infinite basis. A new neural network topology is employed, and criteria for selecting both the data used for training and the trained neural networks for statistical analysis of the results are formulated. The approach is tested by extrapolating the deutron ground state energy in calculations with the Nijmegen II NN interaction and provides statistically significant results. This technique is applied to obtain extrapolated ground state energies of 6Li and 6He nuclei based on the NCSM calculations with Daejeon16 NN interaction.

Compact ultrafast neutron sources via bulk acceleration of deuteron ions in an optical trap

A scheme for a quasi-monoenergetic high-flux neutron source with femtosecond duration and highly anisotropic angular distribution is proposed. This scheme is based on bulk acceleration of deuteron ions in an optical trap or density grating formed by two counter-propagating laser pulses at an intensity of ∼1016W/cm2 in a near-critical-density plasma. The deuterons are first pre-accelerated to an energy of tens of keV in the ambipolar fields formed in the optical trap. Their energy is boosted to the MeV level by another one or two laser pulses at an intensity of ∼1020W/cm2, enabling fusion reactions to be triggered with high efficiency. In contrast to previously proposed pitcher–catcher configurations, our scheme can provide spatially periodic acceleration structures and effective collisions between deuterons inside the whole target volume. Subsequently, neutrons are generated directly inside the optical trap. Our simulations show that neutron pulses with energy 2–8 MeV, yield 1018–1019n/s, and total number 106–107 in a duration ∼400 fs can be obtained with a 25 μm target. Moreover, the neutron pulses exhibit unique angularly dependent energy spectra and flux distributions, predominantly along the axis of the energy-boosting lasers. Such microsize femtosecond neutron pulses may find many applications, such as high-resolution fast neutron imaging and nuclear physics research.

Using students’ critical aspects to deepen understanding of nuclear physics concepts

Abstract Identifying students’ understanding provides a pathway to develop focused teaching to facilitate conceptual understanding. This study aimed to gain more insight into undergraduate students’ conceptual understanding of two nuclear physics concepts. Literature shows that students face difficulties in learning and understanding them. These concepts are nuclear binding energy (NBE) and nuclear force (NF). Phenomenography was used to provide a special qualitative research approach to exploring students’ in-depth understanding, which was not addressed in previous studies. Data were collected from purposively selected students (N = 30) through semi-structured interviews. Phenomenography was used to reveal the different ways in which students’ understand these concepts and serves as indicators of potential conceptual difficulties. Based on these, the relevant and irrelevant critical aspects discerned by students were identified using the variation theory of learning. These critical aspects illustrated how the students understood each concept. For instance, NBE is the energy that must be added to a nucleus to separate it into its constituents and relates to a relevant critical aspect. But, NBE is the energy that binds nucleons and this relates to an irrelevant critical aspect. These critical aspects can provide crucial information that can assist physics instructors in developing focused teaching and learning strategies. Thus, the responses to the interview can be used as a basis for teaching and learning nuclear physics concepts.

Using students’ critical aspects to deepen understanding of nuclear physics concepts

Abstract Identifying students’ understanding provides a pathway to develop focused teaching to facilitate conceptual understanding. This study aimed to gain more insight into undergraduate students’ conceptual understanding of two nuclear physics concepts. Literature shows that students face difficulties in learning and understanding them. These concepts are nuclear binding energy (NBE) and nuclear force (NF). Phenomenography was used to provide a special qualitative research approach to exploring students’ in-depth understanding, which was not addressed in previous studies. Data were collected from purposively selected students (N = 30) through semi-structured interviews. Phenomenography was used to reveal the different ways in which students’ understand these concepts and serves as indicators of potential conceptual difficulties. Based on these, the relevant and irrelevant critical aspects discerned by students were identified using the variation theory of learning. These critical aspects illustrated how the students understood each concept. For instance, NBE is the energy that must be added to a nucleus to separate it into its constituents and relates to a relevant critical aspect. But, NBE is the energy that binds nucleons and this relates to an irrelevant critical aspect. These critical aspects can provide crucial information that can assist physics instructors in developing focused teaching and learning strategies. Thus, the responses to the interview can be used as a basis for teaching and learning nuclear physics concepts.

Measurement of cross-section of the 6Li(d,α)4He, 6Li(d,p)7Li, 6Li(d,p)7Li*, 7Li(d,α)5He, and 7Li(d,nα)4He reactions at the deuteron energies from 0.3 MeV to 2.2 MeV

The interaction of a deuteron beam with lithium is characterized by a high yield of neutrons, high energy of neutrons and a large variety of reactions. The reliable data of the reactions cross-sections are important for many applications, including radiation testing of advanced materials and equipment. The experimental data on the cross-sections differ greatly from one author to another; for a number of reactions there is no data on the cross-section in the databases. Measurements of the reactions cross-sections were carried out at the accelerator-based neutron source VITA at Budker Institute of Nuclear Physics (Novosibirsk, Russia) using an α-spectrometer. The 6Li(d,α)4He, 6Li(d,p)7Li, 6Li(d,p)7Li*, 7Li(d,α)5He, and 7Li(d,nα)4He reactions cross-sections at deuteron energies from 0.3 MeV to 2.2 MeV have been measured. The obtained data are presented tabular form.

Modelling Gd-diamond and Gd-SiC neutron detectors

A custom Monte Carlo (MC) computer model was developed to simulate thermal neutron absorption in, and subsequent photon and electron emission from, natural Gd with a view to using the material as a neutron conversion layer for neutron detectors. The MC code also modelled photon and electron detection with two dissimilar detectors: a thick (500 μm) single crystal diamond detector; and a thin (5.15 μm) commercial off the shelf (COTS) 4H–SiC photodiode detector. The detectors’ quantum detection efficiencies (QE) for hard X-rays and γ-rays were relatively low in comparison to their QE for electrons, thus making it possible to collect electron spectra from the Gd layer neutron conversion products which were not overwhelmed by photon emissions from the Gd. The MC code was utilised to determine the optimal thickness of Gd for the efficient detection of a thermal neutron flux. These radiation hard and spectroscopic detectors paired with natural Gd could find utility as robust and compact thermal neutron detectors for nuclear science and engineering, space science, and other applications.

A novel irradiation module for ANICCA fuel cycle code based on multi-task learning

This paper introduces an alternative approach to irradiation modelling within the context of nuclear fuel cycle codes like ANICCA, the fuel cycle code developed by the Belgian Nuclear Research Centre (SCK CEN). The focus lies on upgrading the irradiation module by substituting the CRAM-based depletion calculations for a more flexible and innovative approach based on Multi-Task Learning (MTL). Utilizing data generated with SERPENT2 Monte Carlo simulations, two MTL neural networks are developed to surrogate irradiation processes of Uranium Oxide (UOX) and Mixed Oxide (MOX) fuels, respectively. MTL enables simultaneous learning of the evolution of the inventories for different observables – i.e., transuranium elements, fission products, minor actinides and fertile materials – offering improved predictive capabilities compared to non-MTL neural networks, as demonstrated in the cross-validation tests.Hyperparameters of the models were found using Bayesian optimization, resulting in superior model performance compared to the old CRAM-based model. Verification against SERPENT2, used as a reference code for comparison, demonstrates the stability and accuracy of the MTL-based models, outperforming the original CRAM method for the majority of predicted isotopes.

Baby skyrmion crystals stabilized by vector mesons

In this letter we study soliton crystals in the (2+1)-dimensional analogue model of the (3+1)-dimensional Adkins–Nappi model of nuclear physics. The baby ω-Skyrme model studied here is an O(3) nonlinear σ model coupled to a massive vector meson, the ω-meson. Using recently developed methods in the (3+1)-dimensional ω-Skyrme model we are able to construct soliton crystals in this (2+1)-dimensional baby ω-Skyrme model. The resulting crystals form a hexagonal lattice structure and are qualitatively and quantitatively similar to crystals observed in the standard baby Skyrme model.