Journal of Contemporary Physics (Armenian Academy of Sciences)最新文献

Diffraction focusing of a spherical X-ray wave on a crystal with a low-angle twist boundary perpendicular to the crystal surface was studied in Laue geometry. It was shown that the diffracted wave propagating behind the crystal is focused not only on a distance corresponding to the focal length of an ideal crystal, but also on greater distances. Moreover, the farther the focus is from the crystal’s exit surface, the lower its intensity.

This work investigates laser control of populations of magnetic sublevels of the ground hyperfine level of the cesium atom on the D₂ line (6S_1/2 → 6P_3/2). A theoretical model is developed within the full density-matrix formalism based on the Lindblad equation, which accounts for coherent interaction with the laser field, spontaneous decay, and decoherence processes. The dynamics of the system is described by a set of coupled ordinary differential equations that reflect the complete Zeeman level structure and the competing relaxation channels characteristic of a realistic multilevel atomic medium. The aim of this work is the controlled redistribution and transfer of population between selected magnetic sublevels while minimizing the population of excited states. To this end, an optimization problem for the laser field parameters is formulated, including pulse amplitudes, frequency detunings, phases, and temporal profiles. Numerical calculations are performed by integrating the high-dimensional system of density-matrix evolution equations. The proposed approach constitutes a scalable computation platform for modeling and controlling Zeeman population dynamics in complex quantum systems and can be applied to problems of quantum state control and preparation.

Laser-induced fluorescence (LIF) was studied in the 400–1000 nm wavelength range using narrow-band 852 nm laser radiation resonant with Cs atomic 6S_1/2 → 6P_3/2 transition. T-shaped cells made entirely of technical sapphire with thicknesses of L = 1 cm, 40 μm, and ~400 nm, containing cesium atomic vapor, were used. It was shown that with the cell thickness decrease (from centimeters to nanometer thicknesses), many LIF signals are suppressed due to an increase in the number of atomic collisions with the walls, leading to quenching of excited states. By recording the LIF signal, it is also possible to estimate the amount of residual Rb atomic vapor (if any exists) in the Cs-containing cell. The Cs vapor cell can serve as an efficient optical frequency converter filter and has other applications.

The study investigates the effect of an ultrasonic field on the synthesis of natural carbonado-type polycrystalline diamond in a toroidal high-pressure chamber under constant pressure, temperature, and holding-time conditions. A method for introducing ultrasound into a toroid-type high-pressure apparatus was developed, ensuring the pressure–temperature parameters (P, T) required for carbonado synthesis. The proposed configuration provides acoustic excitation of both the rod and the graphite, implementing an axial waveguide energy-transfer mode and maximizing radial diffusion processes. An optimal range of amplitudes (1–1.5 μm) and frequencies (200–300 kHz) was determined, resulting in up to a 50% increase in product yield compared with synthesis performed without ultrasonic treatment. A significant improvement in the mechanical strength and performance characteristics of the synthesized carbonado-type polycrystalline diamond was also established.

Studies on the synthesis of high-purity materials have shown that cerium oxide-doped zinc and zirconium silicate nanopowders can be used as pigments for solar reflectors in spacecraft. This has created the need to investigate their radiation resistance. The hydrothermal microwave-assisted synthesis of pure and cerium-doped zinc orthosilicate and zirconium silicate is described. The elemental composition of the materials was determined by instrumental neutron activation analysis. The paper presents the results of simulations of radiation effects on modified composite thermal-control coatings based on cerium-doped zinc orthosilicate (willemite) and zirconium silicate (Zn₂SiO₄:Ce and ZrSiO₄:Ce). The theoretically predicted power-law dependence of the energy spectrum of atoms (ions) that acquired excess kinetic energy is consistent with the simulation results when only Coulomb scattering is taken into account during radiation exposure. The simulations also yielded the probabilities of defect formation in the crystals. Proton irradiation was found to produce the most severe damage to the crystal structure. The damaging effect of electrons is 4–7 times weaker, while that of neutrons is more than 70 times weaker. The simulation code is based on the GEANT4.11 software package.

We studied the generation of high-order harmonics in hexagonal graphene quantum dots interacting with an intense linearly polarized electromagnetic wave. We used the tight-binding mean-field approximation to account for the many-particle Coulomb interaction. Our detailed analysis of the spectrum reveals the multiphoton resonant nature of harmonic generation, shedding light on the underlying quantum processes. The obtained results show that a 96-atom quantum dot exhibits a significant increase in high-order harmonic emission compared to the previously discussed graphene quantum dots.

The results of an experimental study of fabricated monolithic perovskite/silicon tandem solar cells with a nanostructured black silicon interlayer are presented. It is shown that the integration of a black silicon layer with an optimal thickness of 530 nm leads to an increase in power conversion efficiency from 26.2 to 27.8% compared to a planar architecture. The main contribution arises from an increase in the short-circuit current density due to reduced reflection and enhanced light absorption at the interface between the subcells. The slight decrease in the open-circuit voltage is attributed to increased charge carrier recombination at the textured surface of black silicon. The experimental results qualitatively confirm the conclusions of the numerical modeling.

We present the results of a theoretical study on the spectral-angular distribution of radiation emitted by bunches of charged particles passing through a dielectric ball in a vacuum. As previously demonstrated, for certain values of the problem parameters, the generated radiation exhibits resonant behavior in narrow frequency ranges when the dielectric ball is non-dispersive. We show that the presence of dispersion can significantly alter the spectral-angular distribution of radiation and substantially increase its total energy over a sufficiently wide frequency range.

This work presents a Continuous Integration and Continuous Deployment (CI/CD) infrastructure for applications and software frameworks based on WinCC Open Architecture, developed at CERN and providing a development and operations (DevOps) approach for control software of the Large Hadron Collider experiments and CERN technical infrastructure. The system automates compilation, testing and deployment of control software, processing millions of lines of source code in several programming languages. A critical dependency chain is demonstrated: reliability of CI/CD infrastructure → quality of detector control system software → correctness of detector monitoring → validity of Good Run Lists formation → amount of data for physics → reliability of scientific results. Implementation of containerized testing pipelines, automated quality control and multi-level repository deployment strategy increased the release frequency by two orders of magnitude while simultaneously improving software quality and reducing expert dependency. A formal model is proposed that links software versions to the operational state of the facility, with formalized requirements for verification, traceability, and reproducibility of releases. The results demonstrate significant improvements in operational safety, development efficiency and maintainability of mission-critical control systems for high energy physics.

An X-ray interferometric method for studying phase-contrast imaging of polymer materials is presented. A plane-parallel plate was placed in one of the interfering beams. It is shown that, in this case, the plate causes a displacement of the moiré fringes relative to those obtained in its absence. The phase shift was determined, and on this basis, the refractive index decrement of the plate material was calculated. Phase-contrast imaging of a polymer cord was also investigated. A special device was developed for positioning and controlling the samples (the plate and the cord) between the interferometer blocks. An expression for calculating the refractive index decrement of the polymer cord material was obtained, and its density was determined.