Bulletin of the Lebedev Physics Institute最新文献

Optoelectrical studies of a hollow-cathode discharge with a grid anode in He are performed at a pressure of 2 mbar. The electron concentration distribution and the intensity of individual He lines are determined both between the electrodes and in the postanode plasma, with the distance between the anode and cathode being varied from 30 to 100 mm. It is found that the plasma behind the anode is formed by low-energy electrons, whose energies are lower than the excitation energy of the emitting helium levels.

Magnetic monopoles g⁺ and g^‒ are likely the primary components of dark matter, which, immediately after their birth, form g⁺g^‒ atoms. These atoms are characterized by an annihilation energy of 2.4 GeV and Lyman-series transition energies of 1.8, 2.1, and 2.25 GeV corresponding to Ly_α, Ly_β, and Ly_γ lines, respectively. The gamma-ray excess observed in the galactic center by the Fermi observatory in the range of 1‒8 GeV with a maximum near 2.4 GeV indicates the presence of magnetic atoms. On galactic scales, magnetic atoms are dark matter. In addition, dark matter must necessarily include familons and light Goldstone bosons with energies ( ll )1 eV, formed during phase transitions accompanying the cooling of the Universe. The emergence of a new research field—the astrophysics of magnetic atoms—is anticipated, along with the presence of such monsters as g⁺e^‒, g^‒e⁺, g⁺μ^‒, g^‒μ⁺, g⁺τ^‒, and g^‒τ⁺.

The energy levels of the ground states of three-particle and four-particle bound states of leptons in quantum electrodynamics are calculated. A variational method with Gaussian basis functions is used for the calculations. The matrix elements of the Hamiltonian are calculated analytically. The computer code is written in MATLAB for the numerical calculations.

Methods for correcting the trajectory of a cryogenic fuel target (CFT) during its injection into the laser focus of an inertial confinement fusion (ICF) facility are studied. One of the approaches involves the use of various electrostatic fields. In our case, the field source is an electrode in the form of a charged needle (U = 500 V). A successful series of experiments is conducted in a test vacuum chamber (P = 10^‒5 Torr, T = 300 K) using glass and polystyrene microspheres (diameter Ø = 0.7–2.0 mm, wall thickness Δ = 10‒15 μm) as surrogate targets. In addition, free-falling microspheres (Ø = 2.0 mm, Δ = 20 μm) are delivered to a special holder located at a given point inside the test chamber. Stable microsphere positioning on the holder is achieved using a charged needle integrated with the holder. The results may find practical application in the development and optimization of advanced systems for high-precision injection delivery of CFTs to the laser focus of existing ICF facilities.

Solutions to the Vlasov kinetic equation for a distribution function with sharp boundaries have been obtained in the form of nonlinear periodic waves. It is demonstrated that the wave amplitude is bounded; furthermore, waves exhibiting maximum amplitude feature sharpening at the wave crest.

In high intensity laser accelerated beams (HILABs), numerous phenomena influence considerably various stages of the acceleration process, impacting beams quality. This study aims to analyze the Bragg-peak dose distribution behavior by characterizing the maximum energy, proton count, and dose distribution in HILAB, focusing on the interaction between suprathermal and relativistic electrons. These events arise from the strong plasma nonlinearity induced by intense laser fields. We employ a theoretical models to simulate proton acceleration combined with Monte-Carlo methods for dose investigation. It is shown that the competition between these factors leads to significant improvements in proton beam stability, producing a high-quality energy spectrum and an optimal Bragg-peak dose distribution, within the range of values for the electron suprathermality and relativistic parameters ((kappa ,theta )) that were optimized numerically.

This paper describes the production and tests performed with the tungsten collimator prototype produced using laser powder bed fusion technology in a converging geometry. This prototype has been tested for being the antiscatter grid for X-ray imaging to reduce background from the scattered photons. The purpose is reducing patient radiation exposure in medical applications. Obtained results are positive, grid provides definitive enhancement in marker detection, which proves to be especially useful with artificially created obstacles to imitate harsher working environments.

The radiation environment inside a manned spacecraft on the proposed orbit of the Russian Orbital Service Station (ROSS) is assessed using Monte Carlo simulation. The calculation is performed using a simplified model of the Service Module (SM) of the International Space Station (ISS) with the Geant4 software toolkit and the SPENVIS space radiation model. The value of the absorbed dose rate in the ROSS orbit is compared with the values obtained within the same ISS SM model for the low and high orbits of the ISS. The comparison shows that the proposed orbit of ROSS results in total absorbed dose values that lie within the range of values obtained for different ISS orbits; however, the component of the absorbed dose associated with galactic cosmic rays increases by several tens of percent.

We discuss the fraction of extragalactic cosmic iron nuclei that reach Earth without fragmentation in extragalactic space. It is shown that for particles with energies E = 10¹⁹ eV, this fraction is significant (approximately 10%), even for sources with redshifts as high as 0.2, and not just for nearby sources. Therefore, when analyzing possible sources of iron nuclei, distant sources must be taken into account.

The feasibility of using machine learning algorithms to pre-smooth the current-voltage characteristic (IVC) of a Langmuir probe before numerical differentiation to obtain the electron energy distribution function (EEDF) was investigated. It was found that the EEDF shape depends strongly on the IVC region used to train the model. Excluding the IVC region corresponding to the electron-saturation branch from the training process reproduces a local EEDF maximum at ~17 eV. Good agreement with the EEDF obtained by the independent splicing method in the energy range of 0 to 23 eV was demonstrated.