卷 80, 编号 9 (2017)

A review of works performed at the Institute for Nuclear Research of the Russian Academy of Sciences and at the International Laser Center of the Moscow State University in the context of the new research area called “nuclear photonics” is presented. Nuclear photonics is based on creation of the new-generation gamma-ray sources which make it possible to solve a number of fundamental and applied problems, including research of low-energy photonuclear reactions, namely, investigation of collective excitations of nuclei near the threshold (pygmy resonances); nuclear safety assurance; production of low-energy positron beams; and phase-contrast X-ray imaging.

For the stable silicon isotopes ²⁸Si and ³⁰Si, the energies and occupancies of single-particle states of the 1d2s shell are determined by analyzing the combined data for the nucleon stripping and pickup reactions. From the results of analysis and the available experimental data, the variation of the 1d2s proton-shell structure with increasing neutron number for the silicon isotopes with A = 26–34 is discussed.

An algorithm for calculating the spectra of neutrons and associated charged particles produced in the target of a neutron generator is detailed. The products of four nuclear reactions ³H(d,n)⁴He, ²H(d,n)³He, ²H(d,p)³H, and ³He(d,p)⁴He are analyzed. The results of calculations are presented in the form of neutron spectra for several emission angles and spectra of associated charged particles emitted at an angle of 180° for a deuteron initial energy of 0.13 MeV.

Fiber optic communication lines on the basis of the Mach–Zehnder intensity modulator can be used in studies of pulsed plasma for transmission of signals from detectors to data acquisition equipment. In this study, a system for transmission of nanosecond signals over fiber optic cables in the ranges of 1550 and 850 nm is demonstrated. A chronographic electro-optical detector is used for recording the signals in the range of 850 nm.

Results concerning the structural and elemental analysis of beryllium samples obtained via different technologies using a Microzond-EGP-10 unit with the help of the PIXE and RBS methods are presented. As a result, the overall chemical composition and the nature of inclusions were determined. The mapping method made it possible to reveal the structural features of beryllium samples: to select the grains of the main substance having different size and chemical composition, to visualize the interfaces between the regions of different composition, and to describe the features of the distribution of impurities in the samples.

The results of numerical simulation of the behavior of a system consisting of a spherical bubble filled with nitrogen or its mixtures with argon and surrounding water under external influence typical of experimental study of single-bubble sonoluminescence are presented. Comparison of the results of calculations and experiments shows that gas heated at the bubble compression stage cannot be regarded as the only source of radiation. This circumstance requires the presence of other, basic, sources. In the polarization model, this is the channel of electrical breakdown in a liquid. Possible electrical effects accompanying the liquid−solid phase transformation in water near the moment of the maximum compression of the bubble are assumed.

A method of elimination of silicon compounds from the anode wire of an aged proportional counter is presented. The aging of a counter with a 70%Ar + 30%CO₂ and a 60%Ar + 30%CO₂ + 10%СF₄ working mixture was stimulated by a ⁹⁰Sr β source. To accelerate the process of aging, the gas mixture flow to the counter was supplied through a pipe with RTV coated wall. As a result, the amplitude of the signal decreased 70% already at accumulated charge of Q = 0.03 C/cm. The etching of the silicon compounds on the wire surface with an 80%CF₄ + 20%CO₂ gas mixture discharge led to full recovery of the operating characteristics of detector and an increase in the lifetime. A scanning electron microscopy and X-ray spectroscopy analysis of the recovered wire surface were performed. In accordance with the results, a good quality of wire cleaning from SiO₂ compounds was obtained.

The reaction γn → π⁰n is investigated both theoretically and experimentally as an important step toward determining the electromagnetic coupling constants of the N* and Δ* resonances [1]. We analyze the data on the collisions of γ quanta with energies between 200 and 800 MeV with a deuterium target collected by the A2 experiment in Mainz, Germany. These complement the data for neutral-pion photoproduction on protons obtained by the same experiment [2].