High-current-density subnanosecond electron beams formed in a gas-filled diode at low pressures

The formation of electron beams in a gas diode filled with various gases at low and medium pressures under the action of nanosecond voltage pulses has been studied. It is shown that subnanosecond pulses of the beam current in helium, hydrogen, neon, nitrogen, argon, methane, sulfur hexafluoride, krypton, and xenon can be obtained both at atmospheric pressure and at a pressure of several units or dozens of Torr. In particular, a beam current density above 2 kA/cm² behind the foil at a pulse duration (FWHM) of 250 ps has been obtained in helium-filled diode. On the passage from the regime of ultrashort avalanche electron beam formation to the vacuum diode regime, the beam current pulse amplitude decreases, while both the beam pulse duration (FWHM) and the pulse front width increase.     

A high-power xenon dimer excilamp

A high-power sealed-off excilamp operating on xenon dimers excited by a barrier discharge and emitting in the vacuum ultraviolet spectral range (λ ～ 172 nm) has been designed, constructed, and tested. The lamp comprises six quartz tubes (emitters) and has a total radiating surface area of 20 × 20 = 400 cm². The average output power density radiated from the surface of each emitter exceeds 120 mW/cm². The total output power of the excilamp immediately upon discharge ignition exceeds 50 W.     

On diffusion theory in inhomogeneous media: Thin-film source of diffusant

Using asymptotic methods in the theory of differential equations, the original solution of the atomic diffusion problem in the semi-infinite inhomogeneous medium has been obtained for the thin-film (instantaneous) source of diffusant and arbitrary coordinate dependence of the diffusion coefficient. We have mathematically estimated the applicability of this solution and compared it numerically with the known exact solution for a particular case of the exponential coordinate dependence of the diffusion coefficient and a trivial case of the constant diffusion coefficient. Based on our analysis, the ranges of annealing times and depths of diffusant penetration for which the suggested approach proves to be correct have been established.     

On the theory of grain-boundary diffusion in nanostructured materials under conditions of saturation of the subboundary region by the diffusant

In this work, which is the continuation of our previous work (Phys. Met. Metallogr. 109 (6), 329–336 (2010)), we give an extension of the theory of the coefficient of grain-boundary diffusion for the case of relatively large annealing times, when the width of the saturated subboundary zone exceeds the characteristic scale of decreasing coefficient of diffusion but no overlap of diffusion zones occurs in the bulk of nanograins. An analysis of the diffusion problem in this case leads to solutions that in form are analogous to the solution of the problem of one-dimensional diffusion along grain boundaries, corresponding to the C regime of annealing in conventional polycrystals but with time-dependent effective parameters (the grain-boundary diffusion width and the grain-boundary diffusion coefficient). It has been shown that the allowance for the existence of a subboundary region of enhanced diffusion leads to a decrease in the depth of the diffusant penetration along the boundary and to a simultaneous increase in the average sheet concentration. Estimates of these diffusion characteristics for nanocrystalline copper are given. Results of numerical calculations of the diffusion problem are presented, which make it possible to establish the field of the applicability of the approach suggested.     

Afterglow emission from xenon, krypton, and argon dimers in nanosecond volume discharge at elevated pressures

The emission characteristics of plasma of a volume discharge initiated by electron avalanche beams in heavy inert gases at pressures up to 1.5 bar have been studied. It is established that more than 90% of the energy radiated in the wavelength range from 120 to 850 nm is emitted from xenon, krypton, and argon dimers. In the case of excited xenon plasma, an output radiation power of ～300 kW and an energy of 45 mJ per cubic centimeter were obtained.     

On possible mechanisms of nanostructure evolution upon severe plastic deformation of metals and alloys

Nondislocation mechanisms of deformation-induced fragmentation of nanostructures in metals upon plastic deformation are discussed. Conditions under which the refinement of nanograins can effectively occur via deformation twinning and/or deformation-induced phase transformations of a martensitic type are considered. It is shown that for each metal system and each deformation method, there exists a limiting nanostructure with a minimum possible average size of nanocrystallites.     

A portable magnetometer

A portable magnetometer to determine magnetic field anomalies is described. The block diagram of the magnetometer and its specifications are presented.     

Capacitive and barrier discharge excilamps and their applications (Review)

The results of studies, development works, and tests of barrier-and capacitive-discharge excilamps radiating in the UV and VUV spectrum regions are presented. The main information on the designs of radiators and generators is presented. The spectral, temporal, and energy characteristics of excilamps based on the emission of KrCl*, XeCl*, XeI*, XeBr*, KrBr*, Xe*₂, Br*₂, and Cl*₂ molecules and the I* atomic line are described. It is shown that the created generators and sealed-off radiators have long service lives. Examples of specific applications of excilamps are presented.