Physics of Particles and Nuclei最新文献

A weight-based algorithm for unfolding neutron spectra from the results of measurements with the Bonner multi-sphere spectrometer is proposed. Measurements are related to the spectrum through a system of Fredholm integral equations of the 1st kind. The energy dependences of the response functions for moderator spheres of different diameters have different extended shapes with mutual overlaps, which makes it difficult to get an appropriate solution for the ill-posed inverse task of spectrum unfolding. To solve the system of Fredholm integral equations we use decomposition of the spectrum into shifted Legendre polynomials and apply the Tikhonov regularization with weighting factors which are based on the condition numbers of the matrix constructed by the spectrometer response functions. It is shown that including the weight factors in the stabilizing functional ensures statistical balancing of the contributions of measurements with moderator spheres of different diameters. This allows one to determine the optimal set of spheres for measurements, as well as to more accurately unfold spectra using a more subtle regularization procedure. The proposed algorithm is used to unfold neutron spectra at the IREN JINR facility.

An inertial electrostatic confinement (IEC) device is often referred to as a portable neutron source and can be used as a research reactor due to its simple structure and low cost. This device includes two electrodes and a feed-stalk. By using a power source, a voltage difference is applied between two electrodes, by means of a feed-stalk connected to the inner electrode. A lot of experimental and simulation research has been done on this device all over the world. In this work, the IEC device is kinetically modeled using the particle-in-cell (PIC) method. This modeling has been done at a constant voltage of –25 kV and pressure range ((1 times {{10}^{{ - 2}}}) to (1 times {{10}^{{ - 4}}}) Torr). According to the obtained results, the number of ions increases with decreasing pressure. At (1 times {{10}^{{ - 2}}}) Torr, the number of ions is equal to (1.03 times {{10}^{{11}}}), while at (1 times {{10}^{{ - 4}}}) Torr, this value increases to (9.35 times {{10}^{{12}}}). This increase in ions shows that the mean free distance increases with the decrease in pressure, and the probability of collision between ions and neutrals decreases.

The present paper discusses the observations on structural transitions in ferronematics (FNs) based on the liquid crystal E7 doped with magnetic goethite nanoparticles. The dielectric properties of the prepared FNs have been investigated under the application of an orienting magnetic field and a DC biasing electric field. It was demonstrated that the addition of nanoparticles substantially influences the sensitivity of FNs to external magnetic fields.

In the present paper, we have studied the nonrelativistic problem for a spin 3/2 particle in presence in the external Coulomb field. The known general procedure for performing the nonrelativistic approximation is based on the method of projective operators. This approach is applied directly in the relativistic system of radial equation derived previously for a free spin 3/2 particle for states with the spherical symmetry within the covariant tetrad formalism. The system of two 2-nd order differential equations describing the nonrelativistic particle has been derived. It refers to states with quantum numbers of energy, square and the third projection of the total angular momentum, and spatial parity. Solutions of radial equations have been constructed in terms of confluent hypergeometric functions, the corresponding energy spectra are found.

This article explores the application of machine learning techniques to the isochronization of the magnetic field in the MSC 230 isochronous cyclotron. The primary objective is to reduce the computational effort typically required for adjusting the magnet geometry in order to achieve isochronicity. By predicting the necessary modifications to the magnet’s geometry, our approach aims to streamline the iterative process. We compare several machine learning models against traditional methods, demonstrating their potential to reduce the number of iterations needed.

Based on the Holstein Hamiltonian, the charge dynamics in a chain of sites is investigated at finite temperatures. Previously, we compared results obtained for canonical ensemble and for microcanonical description. According to the simulation results, the transition from the polaron mode to the delocalized state occurs in the same range of thermal energy values of a chain of (N) sites with the adjustment: for the microcanonical description the temperature does not correspond to the initially set one, but is determined after long-term calculations from the average kinetic energy of the chain. In this paper, mixed model is considered: first, a polaron is automatically formed in a short chain with Langevin thermostat. Then, the chain is extended by sites with the same temperature. Dynamics of this system in the microcanonical approach, i.e. for a chain in a vacuum, leads to polaron desruption and cooling of the chain. Such effect may be useful in the design of a molecular DNA refrigerator.

This paper presents a detailed examination of difference schemes that establish a one-to-one correspondence between time layers, commonly known as Kahan’s method or reversible difference schemes. These mathematical frameworks play a crucial role in numerical analysis and computational mathematics, enabling accurate modeling of dynamic systems. The paper discusses the applications of these schemes, particularly in dynamic systems with quadratic right-hand sides, which are found in various fields such as physics, engineering, and applied mathematics. These systems often describe complex phenomena, including mechanical vibrations and fluid dynamics. Additionally, the study explores the integration of Kahan’s method with the direct method for solving partial differential equations (PDEs) in mathematical physics. This combination aims to enhance the accuracy and computational efficiency of numerical solutions. By investigating the correlation between these methodologies, this work seeks to advance numerical techniques for addressing complex dynamic systems. The findings indicate that this integration improves the stability and convergence of solutions, highlighting the potential of Kahan’s method and reversible difference schemes in tackling challenges across diverse scientific disciplines.

The dynamics of microtubules is considered in the frameworks of the longitudinal model. By using the approximation of the slowly varying envelopes, we obtain the approximate solution of the model equation in the form of the oscillating kink. The evolution of this solution is compared with the results of the numerical simulation. Several types of the dynamics of the oscillating kinks, which are determined by the parameters of the approximate solution, are identified.

Inclusive jets production in proton-proton collisions at an energy of (sqrt s = 27) GeV in the SPD experiment was studied. The study was performed on the simulation of the (qg to gamma q) process and all QCD processes using the anti-({{k}_{{text{T}}}}) algorithms by Pythia8 generator. The results include determination of kinematic characteristics of hard-scattered partons based on jets properties and with machine learning methods.

Direct computational simulation in naval aerohydromechanics can serve as an available toolkit for engineering research both in the design of new marine equipment and in storm tests, replacing model and full-scale experiments. The latter is due to the increased power of computing systems and the level of detail of mathematical models possible for computer realization. The paper presents an interactive computational environment for modeling the dynamics and control of ship maneuvering. This virtual testbed can be considered both as a navigator’s expert environment and as a simulator for improving skills of effective and safe ship navigation in storm conditions. The paper discusses a reasonable balance between the detail of the applied computational models and computational efficiency. The proposed approach can be implemented in various physical fields, where it is required to develop a virtual testbed to study the behavior of complex technical objects: transport systems, experimental facilities of high-energy physics, etc.