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Vol 525, No 1 (2025)
ФИЗИКА
On the unpredictability of quantum measurement outcomes
Abstract
The paper addresses the issue of stochastic behavior in quantum systems. The causes of the unpredictability of measurement outcomes in quantum mechanics are analyzed. The fundamental postulate of quantum mechanics is formulated, and on its basis a clear and consistent general concept of measurements in quantum mechanics is developed. The principles of designing an instrument that operates in accordance with Bohr's postulates are outlined. A model of the corresponding measurement process is proposed in the simplest case of a spin 1/2 particle in a constant magnetic field. It is shown that there is no difference between the nature of the stochastic behavior of quantum and classical systems.
5-10
Inversion of surface conductivity type in correlated topological insulator SmB6
Abstract
The potential to control the type of surface conductivity in the correlated topological insulator SmB6 was demonstrated for the first time. The transition to p-type surface conductivity with the Hall effect sign inversion at helium temperatures was achieved by cleaning the SmB6 faces formed by the (110) surfaces with the help of argon ion sputtering with an average energy of 500 eV. The crossover in the surface conductivity type with a dominant contribution from surface holes (having mobility up to 60 cm2V−1s−1 at 2 K) is associated with both the removal of carbon from the surface of SmB6 and its passivation by oxygen, and with the generation of defects in the near-surface layer initiated by ion bombardment. The discovered effect opens up possibilities for modifying the parameters of surface electron transport in the correlated topological insulator SmB6 by means of the controlled injection of defects or due to the field effect.
11–20
Study of laser cavitation process using numerical simulation
Abstract
The work presents a numerical simulation of the process of growth and collapse of a vapor bubble that occurs at the tip of an optical fiber (laser heating element) immersed in water. The constructed numerical solutions allow us to find the temperature field distribution in a superheated liquid when a bubble appears, and to obtain the values of the velocity and temperature of the cavitation jet that occurs when the bubble collapses.
21-30
Parameters of fast electrons on “MIC” facility
Abstract
The paper presents the results of experiments with fast electrons generated by laser radiation with energy of about 30 kJ, intensity of 3·1014 W·cm−2 and duration of 5 ns focused on a metal target. It is shown that in the evacuated interaction chamber a flux of electrons, having energies of about 10 keV and a neutralized spatial charge and diverging over distances of meters from the target, is formed. The amplitude of the generated current is about one hundred megadampers, which also indicates a complete current compensation of the electron flux. According to the estimates, the charge neutralization and the current compensation can be provided by weakly ionized plasma formed in the interaction chamber due to residual gas when pumping the chamber to a pressure of 10−3 Torr. The effect of generating such electron fluxes is of interest for radiation-related applications and academic problems related, for example, to the development of filament instability in plasma.
31-37
Experimental modeling of cavitation effects in an underwater explosive eruption
Abstract
As an experimental model of a volcanic eruption, the Electro-Magnetic HST method was used, the scheme of which includes optically transparent cuvettes with a metal bottom, a layer of distilled water and a battery of high-voltage capacitors. Under the bottom there is a “charge” in the form of a flat spiral, onto which, when closed by a high-voltage pulse of a break in the circuit, a battery of capacitors is discharged, forming a shock wave and a quasi-empty rupture, the growth of which is accompanied by a continuous decrease in pressure. The experiments recorded a detailed process of focusing a quasi-empty cavity with a smooth increase in pressure both inside it and in the shell bubbles, and the rapid transition of the latter into a dust cloud. The formation of SW ends in the form of a clear annular boundary on the surface of the cuvette bottom. The formation of toroidal bubble clusters, their separation from the bottom of the layer and a breakthrough into free space.
38–44
Laser ultrananoablation of diamond free from generation of color centers
Abstract
The process of nanoablation of the diamond surface by UV laser pulses of nanosecond duration with a high repetition rate is investigated. Special attention is paid to the change of fluorescent properties of diamond in the irradiation zone. It was found that at a comparable etching rate (10–7...10–4 nm/pulse) irradiation by nanosecond pulses does not lead to the generation of color centers (in particular, NV centers) which are produced in significant quantities when exposed to femtosecond pulses. The features of ultrananoablation at low pressures are analyzed and a noticeable change in the optical properties of the diamond surface in the impact zone is noted for the first time, that is associated with the formation of a surface nanorelief and quasi-periodic structures (~100 nm).
45-54
Flow pattern evolution of a nanoparticle suspension drop with water merging in the impact flow mode
Abstract
The evolution of the substance transfer pattern at the initial stage of merging a drop of nanofluid — a suspension of iron oxide nanoparticles — with tap water was tracked using high-speed video recording for the first time. Experiments were performed in the impact mode, when the kinetic energy of the drop significantly exceeds its potential surface energy (PSE). During merging, the nanofluid drop disintegrates into thin trickles, traces of which form linear and mesh structures on the surface of the crown and cavity. The trickles pierce the walls of the cavity and penetrate into the thickness of the liquid, where they form an intermediate layer. The general geometry of the flow is consistent with the coalescing pattern of a drop of electrolyte — a dilute solution of potassium permanganate. The evolution of the structure over time was traced at the initial stage of drop merging.
55-69
A new representation of the thermodynamic potential of lithium niobate
Abstract
Within the framework of the phenomenological theory new thermodynamic models of lithium niobate with Landau potentials of the fourth and sixth degrees have been constructed. The coefficients of these potentials have been calculated using known experimental values of the material constants of the linear equations of the piezoelectric effect, as well as electro-optical and acousto-optical constants obtained at room temperature. When constructing the potentials, the temperature behavior of the permittivity, spontaneous polarization and deformation has been taken into account. Both potentials allow calculating the full set of piezoelectric, electro-optical and acousto-optical constants of lithium niobate in a wide range of temperature changes. Computational experiments have been carried out to calculate the deformation and spontaneous polarization in the range of 300–1400 K. The results of calculations obtained using the sixth-degree potential have shown good agreement with the results of experimental studies.
70-79
ТЕХНИЧЕСКИЕ НАУКИ
Nitriding of iron under conditions of thermal coupling of self-propagating high-temperature synthesis processes: phase and elemental composition, magnetic properties
Abstract
Direct nitriding of micron-sized carbonyl iron powders with spherical particles was carried out under conditions of thermal coupling of self-propagating high-temperature synthesis processes. Urea was used for iron nitriding. The nitriding products are composite materials based on the α-Fe, ε-Fe3Nx, Fe3C and Fe4N phases. X-ray phase analysis and chemical analysis methods showed that when the urea content is more than 15 wt. %, iron carbonitride ε-Fe3NxC1-x is formed in a mixture with iron, in which the nitrogen atoms in the ε-Fe3Nx crystal lattice are partially replaced by carbon. The iron nitriding products are soft magnetic ferromagnetic materials and have high values of specific magnetization from 142 to 157 emu/g.
80–87
Electron microscopic study of the contact zone "plasma coating (molybdenum high-speed steel) – substrate (medium carbon steel)"
Abstract
The structural and phase states, as well as the elemental composition of the transition zone in the "plasma coating (molybdenum high-speed steel) – substrate (medium carbon steel)" system, have been investigated. It has been established that the transition layer, approximately 100 μm thick, contains an α-phase, γ-phase, complex carbide phases (Me23C6, Me6C), as well as MoC and cementite. No microcracks or microdiscontinuities were detected in the transition layer.
88-96