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

In previous works, the electromagnetic field in an arbitrarily chosen volume is represented in vector form including surface and volume integrals using the found vector Green’s function. Surface integrals describe the diffraction of the field created by charges external to the volume, and volume integrals describe the fields created by charges moving inside the volume. In this work, passing to the Fourier transforms in the previously found vector formulas of the field, expressions for a monochromatic electromagnetic field are obtained. Integro-differential equations are also obtained for a monochromatic electromagnetic field in a non-magnetic medium, in the presence of charges with a given motion. Because both diffraction fields and the fields of charges with a given motion, as well as the fields of charges induced in the medium, are considered together, these equations are obtained for the first time.

The modeling calculation of cross-sections of residual nuclei for isotopically enriched lead (²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb) targets irradiated by 2.2 GeV/nucleon deuteron beam has been made by the Monte Carlo N-Particle Transport Code (MCNP). The experimental results were obtained on the Nuclotron of the Laboratory of High Energy Physics at the Joint Institute for Nuclear Research in Dubna. The production cross-sections of target fragments were determined for about 90 residual nuclei on each target mentioned above by the method of induced activity. The first-time irradiation has been made on the ²⁰⁴Pb in the GeV range. The comparison of theoretical computations and experimental results showed good agreement between the experiment and simulation data.

Rare decays of B-mesons allow one the investigation of physics outside of the SM. For (B to {{X}_{s}}{{gamma gamma }}) processes, the potential new physics should be visible not only for the width of the decay but also in the differential distributions for the parameters (({{s}_{1}},{{s}_{2}})), defined as ({{s}_{i}} = {{({{p}_{b}} - {{q}_{i}})}^{2}}{text{/}}m_{b}^{2}), (i = 1, 2), where ({{p}_{b}}), ({{q}_{1}},{{q}_{2}}) are the momenta of the b-quark and the two photons. In this work, the contribution of the order ({{{{alpha }}}_{s}}) of the interference of the operators ({{O}_{7}} - {{O}_{8}}) was calculated. We also consider the dependence of the results from the mass of the s-quark by changing ({{m}_{s}}) in the range of 400–600 MeV. The contribution of the interference of the operators ({{O}_{7}} - {{O}_{8}}) into the width of the decay (B to {{X}_{s}}{{gamma gamma }}) in the regions of the phase space considered is equal to 2–3%.

The results of the simulation of heat propagation processes in the multilayer detection pixel of a single-photon thermoelectric detector consisting of heat sink (Bi-2223), thermoelectric sensor (CeB₆), absorber (Bi-2223), and antireflection layer (SiO₂) arranged in series on sapphire substrate (Al₂O₃) are presented. The design of the detection pixel without an antireflection layer is also considered. Simulation of the processes of absorbed photons heat transfer is carried out based on the equation of heat propagation from a limited volume. The cases of absorption of photons with energies of 0.8–1000 eV in detection pixels with a surface of 4 and 1 µm², different thicknesses of absorber and sensor at a fixed operating temperature of the detector of 9 K are studied. Temporal dependences of voltage arising on the sensor, the equivalent power of Johnson and phonon noise are investigated, the signal-to-noise ratio is calculated, and the ways to increase this parameter are proposed.

The Jaynes-Cummings (JC) model is presented based on quantized counterpropagating waves, characteristic of a ring resonator. This model, in addition to the Hamiltonian and the operator of the number of excitations, includes an interference operator whose eigenvalues imitate the term cos 2kz of the classical picture of the field. The average number of photons, dispersion, the Mandel parameter Q, and atomic-photon entanglement in states with certain excitations are considered. The collapses and revivals are revealed, which in the standard JC model are present only in states with an indefinite number of excitations. It is shown that photons at the boundary energy levels are antibunched (with Q ≈ –1/2) regardless of the system’s parameters, and photons of other energy levels are grouped to the degree that grows with the total number of photons.

The vibrating wire monitors are used for measuring transverse pro-files of radiation beams of different nature. For increasing the accuracy of scanning, and in some cases escaping the scanning procedure (measurement of the beam profile using a matrix of wires), it is proposed to use several vibrating wires. A monitor of this kind with two vibrating wires spaced apart at some distance formed the measuring unit of the laboratory stand, developed by us for training students in accelerator technology. The features of such a two-wire monitor and, in particular, the problem of laser radiation power redistribution between the wires are discussed.

For the process of nondegenerate parametric decay in an optical cavity in which a photon with energy (hbar {{{{omega }}}_{3}}) decays into two photons with energies (hbar {{{{omega }}}_{2}}) and (hbar {{{{omega }}}_{1}}), where (hbar {{{{omega }}}_{3}} = hbar {{{{omega }}}_{2}} + hbar {{{{omega }}}_{1}},) the possibility of forming entangled field states of the interacting modes of the optical system based on the variable of quadrature amplitudes is studied. It is shown that strongly entangled states are obtained between the modes with the frequencies ({{{{omega }}}_{2}}) and ({{{{omega }}}_{1}}) in the case of a very strong coupling of the interacting modes. Weakly entangled states are formed in the case of strong coupling between modes, and no entanglement of these modes occurs in the case of weak coupling. In the optical system, the entangled states by the variable of quadrature amplitude do not form for the modes with frequencies ({{{{omega }}}_{3}}) and ({{{{omega }}}_{1}}).

Semitransparent gray color obsidian samples (bulk and powder) were irradiated at room temperature by Co⁶⁰ radiation source with the γ-photon average energy of 1.25 MeV and different doses from 5 to ~500 kGy. It is known that γ-irradiation influences the optical properties of glass materials depending on the composition as well as on the presence of defects in the glass matrix. Analysis of obsidian samples was carried out by absorption and reflection spectroscopy in the UV, visible, and IR ranges, as well as by EPR measurements for characterization of semitransparent gray color obsidian depending on the γ-irradiation of different doses. The difference in transmittance spectra between the pristine sample and those irradiated with different doses made it possible to distinguish three absorption bands at 368, 386, and 442 nm, which are responsible for Fe³⁺ ions in different environments. The content of hydroxyl OH groups, determined from the absorption in the band at ~4500 cm^–1, does not change in the range of used doses. The EPR measurements showed three signals with g-factors of ~6.0, ~4.2, and ~2.0 characteristic for Fe³⁺ ions, the intensities of which increase with increasing irradiation doses. Obsidian turned out to be resistant to the formation of NBOHC paramagnetic defects in the region of the indicated doses of γ-irradiation.

An X-ray three-block interferometer with a thin neck between the analyzer and mirror blocks is designed. The mutual arrangement of these blocks is changed with the help of levers with weights at the ends, which made it possible to rotate the analyzer block with the splitter blocks (S) and the mirror block fixed. Sectional topograms of interference patterns at different torques show that rotational moiré prevails in the recorded moiré patterns. With an increase in the mechanical torque, the period of the moiré fringes increases; at some moment, the moiré pattern disappears, and the interference field becomes uniform, which means that the interferometer becomes an “ideal”: further increase in the torque results in the appearance of a rotational moiré with a change in the sign of the slope of the interference fringes. A theoretical interpretation of all observed phenomena is given.

Single phase and highly transparent ZnO:Tb films with a Tb concentration from 0.41 at% up to 0.78 аt% were formed on glass and silicon substrates by sol-gel deposition. The influence of ultraviolet radiation on the structural and photoelectric characteristics of n-ZnO:Tb/n-Si structures has been studied. The appearance of a photoelectric effect under the influence of a bias voltage and UV radiation (405 and 278 nm) was established, with an increase in photo effect when irradiated with shorter wavelength UV radiation (278 nm). It was shown that the concentration of the Tb³⁺ dopant is the determining factor for increasing the UV photosensitivity of the structures. The experimentally established selective sensitivity of n-ZnO:Tb/n-Si structures to UV radiation with a wavelength of less than 405 nm demonstrates the possibility of their use in UV radiation detectors or sun-blind detectors.