Vol 46, No 1 (2019)

The dependence of the pulse shape of laser radiation of a CdS semiconductor target on the parameters of the exciting subnanosecond electron beam (EB) is studied. The effect of the time to reach the threshold excess carrier density (ECD) on the laser radiation pulse shape is considered. A train of laser radiation pulses with a maximum intensity to 10⁷ W/cm² is obtained at modulating EB pulses by a frequency of 5 GHz. It is shown that an increase in the ECD during the lifetime can be used to further increase the intensity and to reduce the laser radiation duration in the picosecond range.

The problem of ion drift in such a strong electric field that the ion drift velocity significantly exceeds the thermal velocity of atoms is considered. In the case where the ion mass is identical to the gas particle mass, scattering is isotropic in the center-of-mass system and the ion scattering cross section is independent of the collision velocity (hard sphere model). The ion velocity distribution function is calculated by the Monte Carlo method, its characteristics and diffusion coefficient are determined. A comparison with known numerical and analytical solutions is performed. It is found that average characteristics (drift velocity, longitudinal and transverse temperatures) are in very good agreement with the values obtained from integral relations for the two-temperature Maxwellian distribution; however, the ion velocity distribution itself differs significantly from the shifted two-temperature Maxwellian distribution.

For the first time, the effect of moisture content in the structure of wood samples on the quality of the results of the study of their internal structure using high-resolution X-ray computer tomography is considered. The tomographic method for determining the internal distribution of the structure and density of tree rings of stem wood can be used to solve problems in the field of dendroclimatology and biometeorology.

The project of the compact space detector for measuring proton (10–100 MeV) and electron (to 10 MeV) energy spectra in solar cosmic rays is presented. The detector can operate in two modes: differential (each event is reconstructed) and integral (only energy spectrum and radiation composition are reconstructed at a high loading).

The possibility of controlling wetting of the surface of a thin layered film consisting of silver and polymer layers at producing a periodic structure using a femtosecond laser is studied.

Using methods for measuring photocurrent and Raman scattering spectra the surface region microstructure of the silicon photovoltaic converter with n⁺—p junction and an antireflective porous silicon film is studied. The n⁺—p junction is formed by thermal diffusion of phosphorus from a porous film. It is found that high-temperature treatment during diffusion results in coarsening silicon crystallites and a decrease in the defect density in the porous silicon film. It is noted that the n⁺ —p junction is formed within the largest crystallites of the porous silicon film.