Bulletin of the Lebedev Physics Institute最新文献

We report an investigation of optical and scintillation characteristics of a prototype module of an electromagnetic calorimeter based on a Lu₂SiO_5‒z:Y³⁺:Ce³⁺:Ca²⁺ crystal with the size of 20 × 20 × 90 mm³ and grown by the Czochralski method. The scintillation decay time of the crystal module excited by gamma quanta by a ¹³⁷Cs source is obtained. The energy resolution of the crystal module is estimated by simulating it with the GEANT4 program.

Based on two different nonempirical (calculated ab initio) interatomic potentials, we study the sensitivity of the line shape of the anomalous light-induced drift (LID) to the difference in interaction potentials using Cs atoms as an example and taking into account the real level structure in the atmosphere of inert buffer gases He, Ne, and Xe. It is found that even a slight difference in the interatomic potentials strongly manifests itself in the frequency dependence of the drift velocity in the region of the anomalous LID. The obtained results make it possible to perform high-precision testing of interatomic potentials based on experiments on the anomalous LID of Cs atoms.

The use of millisecond laser sources has become an essential part of clinical practice in assisted reproductive technologies. The biopsy of embryos at the blastocyst stage is one of the challenges addressed in reproductive medicine. We have examined the feasibility of applying femtosecond laser pulses (with a duration of 280 fs and a radiation wavelength of 514 nm) and their effectiveness in solving this problem. The biopsy procedure was performed using micropipettes as part of a standard clinical protocol. It is demonstrated that pulses with an intensity of 4 to 6 TW/cm² can be used to separate bioptate cells. The outcomes of exposure in different regimes (from a single pulse to a sequence of pulses) are presented.

We report a study of a soliton-like regime of second harmonic generation in a crystal containing impurity atoms with a quantum transition, which is quasi-resonant with respect to a laser pulse at the fundamental frequency. Mismatches of phase and group velocities are taken into account. It is shown that quasi-resonant impurities, on the one hand, lead to a decrease in the generation efficiency, and, on the other hand, they are capable of creating conditions for the implementation of a two-frequency soliton regime, which is impossible in their absence.

We report a comparative study of the impact of repetitively pulsed neodymium laser radiation of the first (λ₁ = 1064 nm, τ₁ = 12 ns) and second (λ₂ = 532 nm, τ₂ = 10 ns) harmonics on tableted microparticles of brown (2B), gas (G), and fat (Zh) coals. The concentration of synthesis gas molecules formed when microparticles of hard coals are exposed to laser pulses of the same energy density is higher in the case of the second-harmonic radiation. The concentration of synthesis gas molecules formed when microparticles of coals are exposed to first- and second-harmonic pulses of the same intensity is the same. A model is proposed to explain the nonlinear dependence of the synthesis gas yield on the intensity of laser pulses, based on the nonlinear generation of primary centers of thermochemical reactions formed during optical breakdown of coal samples and generation of laser-induced plasma. The spectral intensity of the laser-induced plasma glow when tableted samples of coal microparticles are irradiated by the second-harmonic laser pulses is higher than that during irradiation by the first-harmonic pulses, with radiation energy densities being the same.

Long-lived electron-beam-induced absorption in a number of UV-optical materials for windows and multilayer coatings of inertial fusion energy reactor and promising KrF laser driver was studied using a pulsed linear electron accelerator with electron energy of 10 MeV. In testing high-purity samples of quartz glasses Corning 7980, KU-1, and KS-4V, as well as crystals of calcium fluoride, magnesium fluoride, and leucosapphire the radiation dose of 18.2 MGy, was comparable to the dose absorbed by windows of KrF electron-beam-pumped laser driver operating for 1 year with a pulse repetition rate of 5 Hz. Quartz glass KS-4V with an admixture of OH showed the lowest absorption with a coefficient of 0.4 cm^–1 at a wavelength of 248 nm among all other glasses. Rather high absorption with a coefficient of 4 cm^–1 in calcium fluoride is effectively bleached by the own KrF laser radiation.

We study the propagation of soft X-rays in conical hollow through nano- and micropores of polymer track membranes. The distribution of the field amplitude and the transmission coefficient of the conical structures are determined. The problem is of interest for two reasons. First, the conical shape of pores in track membranes is the norm rather than an exception to the rule. It is determined by the final ratio of the etching rates of the intact polymer and the membrane material in the track region. Secondly, the concentration of soft X-rays at the output from the conical pores of the sample has been scarcely studied. Calculations are performed for porous membranes made of polyethylene terephthalate at wavelengths of 13.3 and 30.4 nm at normal incidence of radiation on the pore end and at various angles of the pore cone. Examples of calculations for oblique incidence of radiation on the sample are presented, and the effect of the damaged pore wall layer on the calculation results is discussed.

We present a spectrum of primary galactic particles with energies of 10 TeV < E₀ < 500 TeV, obtained from the data of reprocessing of events related to nucleon‒nucleus interactions measured in four X-ray emulsion chambers (RECs) exposed in the stratosphere at ∼10 g/cm² for 6‒7 days in the Russian‒Japanese RUNJOB balloon experiment. The spectrum agrees within statistical errors with the proton spectrum published on the results of the final processing of the RUNJOB experiment [1]. The presented spectrum of galactic particles includes events with found and missing single-charged primary particles in nucleon‒nucleus interactions, and is compared with the spectrum constructed only from events with detected primary protons and the final spectrum of the cosmic ray proton component of the RUNJOB experiment.

The present work reported the preparation of Sm-doped zinc oxide (ZnO:Sm) nanoparticles using a chemical precipitation method. Particle size, morphology, luminescence and optical properties are studied. The role of doping concentration on the antibacterial and photocatalytic properties is explored. The atomic doping concentration of Sm is chosen as 0, 1, 3, and 5%. The uniformity and grain sizes of the prepared nanoparticles are effectively controlled by doping. Violet, blue and greenish yellow emissions are observed in the photoluminescence spectrum. The band gap of the material ranges from 3.322 to 3.143 eV as the doping concentration of Sm changes from 0 to 5%. The electron and hole concentrations are examined. The prepared nanoparticles have a high refractive index and are examined using various models. Antibacterial studies against the bacteria that cause the disease septicemia have been reported. The enhanced photocatalytic performance is observed. A maximum of 94% of the degradation of methylene blue is obtained using ZnO:Sm (5%) nanoparticles.

After achieving thermonuclear ignition in inertial confinement fusion (ICF), a new stage of research began, the ultimate goal of which is creation of an industrial ICF reactor for generating electric energy. This work is devoted to radiation stability of the optical components of ICF reactor chamber and a promising KrF laser driver as one of the unsolved problems along this path. The adaptation of a ten-megaelectronvolt pulsed linear electron accelerator with an average power of 15 kW for testing a number of optical materials transparent to UV radiation of KrF laser is described. With a peak electron beam power of 4 MW and a repetition rate of 8-μs pulses of 50 Hz, the accelerator provided a maximum dose rate of electron irradiation of materials of 2.5 kGy/s at controlled temperature of optical samples under conditions close to the operation of KrF laser driver windows. The results of current and dosimetric measurements are in good agreement with Monte Carlo calculations.