[en] Research has been made into the tendency to temper brittleness of complex-alloyed steels 20Kh3MVF, 25KhMF, 20Kh2N4MA, 38KhN3MFA within the temperature range of from 500 to 650 deg C. The steels 20Kh3MVF and 25KhMF exhibit the tendency to temper brittleness within the temperature range studied. The maximum embrittlement is observed at higher temperatures (620-650 deg C) as compared with the temperature of the nonreversible temper brittleness. This shift is explained by the presence in the composition of the steels, of a great proportion of elements forming special carbides whose coagulation occurs at a higher temperature. The steels of the grades 20Kh2N4MA and 38KhN3MFA have no tendency to temper brittleness

[en] The cross sections and rate constants for quenching ⁴He(2¹S), ⁴He(2¹P), ³He(2¹S) and ³He(2¹P) states by collisions with ground state Ne atoms are measured by a time-resolved method in a He-Ne electron beam excited plasma at low pressure. These rate constants at T_g=600 K are: k_⁴He(2¹S)=(1.6±0.2)x10^-10, k_⁴He(2¹P)=(3.4±2.5)x10^-10, k_³He(2¹S)=(1.6±0.2)x10^-10 and k_³He(2¹P)=(5.7±1.2)x10^-10 cm³ s^-1. The cross sections derived from the rate constant are σ_⁴He(2¹S)=(8.4±0.8)x10^-16, σ_⁴He(2¹P)=(1.8±1.3)x10^-15, σ_³He(2¹S)=(7.1±0.9)x10^-16 and σ_³He(2¹P)=(2.6±0.5)x10^-15 cm², respectively. The diffusion coefficient of ³He(2¹S) in ³He is estimated to be D_{³He(2¹S)-³He}=1.9D_{⁴He(2¹S)-⁴He}, based on comparison with ⁴He. A time-dependent collisional radiative model for an e-beam sustained He-Ne plasma is developed and the predicted line intensity of NeI λ=6328 A line is compared with the experimental data. The influence of different processes involved in population and depopulation dynamics of He(2¹S) state are evaluated

[en] Penning recombination lasers (PRL), as first proposed in, operate in non-equilibrium recombination plasma where the upper laser level (ULL) is populated by the recombination flux and the lower laser level (LLL) is depopulated by Penning reactions. The lack of chemical activity and degradation of the laser mixture, lasing in the visible spectral region and high output power obtained attract the attention to the Ne-H₂ PRL operating on the NeI 585.3 nm line (the 2p₁-1s₂ transition). Despite the most powerful PRL are pumped by electron beams of relativistic energies, it is of practical interest to realize PRL pumped in a hollow cathode discharge where beam of high energy primary electrons exists. In this study a detailed experimental investigation of a Ne-H₂ PRL operating in a helical hollow cathode discharge is carried out. The obtained data are compared with the results of the theoretical model. The laser tube design is similar to that used in our previous work. The cathode is made of Mo band 10 mm wide, helically wound with a 15 mm pitch to form a cylindrical hollow. Five laser tubes with different cathode diameters (5.5-12 mm) and lengths (110-280 mm) are investigated

[en] The Penning Recombination Laser (PRL) requires the presence of both a recombination plasma populating the upper laser level (ULL) and a gas component efficiently depopulating the lower laser level (LLL) by Penning reactions. Such requirements are met in the negative glow plasma of a pulsed high voltage Ne-H₂ discharge with a helical hollow cathode. High rates of ionizations followed by recombinations are reached due to the beam component of non-Maxwellian electrons of 1-2 keV energy present in the tail of the electron energy distribution function. The H₂, on the one hand plays the role of Penning component and on the other hand effectively cools the electrons by rotational and vibrational levels excitation. The latter contributes to the effectiveness of the recombination processes. A kinetic model of the physical processes determining the inversion population on the NeI(2p₁-1s₂) transition (the 585.3 nm line) in a Ne-H₂ PRL operating in a high voltage hollow cathode discharge at intermediate pressures is proposed. About 60 plasma-chemical reactions are considered in the model. These include: two-electron recombination of Ne⁺; dissociative recombination of Ne₂⁺, NeH⁺ and H₂⁺; ion-ion recombination of Ne⁺ and H^-; Ne and H₂ direct ionization by fast electrons; Ne stepwise ionization; Penning ionization; Ne excitation by fast electrons; Ne stepwise excitation and de-excitation; radiative transitions; electron mixing between Ne excited states; H₂ rotational and vibrational levels excitation; H₂ dissociative attachment; elastic electron collisions with H₂ and Ne. The rate constants for the reactions are either taken from the literature or calculated in this work

[en] The dynamics of Xe clusters irradiated by a high intensity subpicosecond laser pulse is investigated through a relativistic time-dependent three-dimensional particle simulation model. In order to explore the effect of transition from underdense to overdense plasma, we performed calculations for laser wavelengths between 100 and 800 nm. The ionization of clusters and charge accumulation was found to be independent of the laser wavelength, while the removal rate of electrons from the cluster into the intercluster space, mean electron and ion energies, and energy absorption increase with the wavelength

[en] Efficient guiding and propagation of multi-keV x-rays in plasmas can be achieved by dynamically modifying the media through plasma channel formation. The dynamics of plasma channel formation is studied in preformed underdense plasma irradiated by a high intensity laser. This is done by a two-dimensional model coupling laser propagation to a relativistic particle-in-cell model. For laser intensity of 10²⁰ W/cm² and a laser beam width of 5 μm the channel formation proceeds on a time scale of 60-70 fs in uniform plasma with density 10¹⁸ cm^-3. The channel closes shortly after the rear of the laser pulse has passed due to Coulomb attraction from the ion core. Electron cavitation occurs only if the laser intensity is above a certain threshold intensity and the laser pulse duration exceeds 100 fs. X-ray generation and propagation is feasible for ultrarelativistic laser pulses with small beam width, less than ∼20 μm, and duration of more than 100 fs

[en] The fusion neutron yield from a compact neutron source is studied. Laser-irradiated deuterium clusters serve as a precursor of high-energy deuterium ions, which react with the walls of a fusion reaction chamber and produce copious amounts of neutrons in fusion reactions. The explosion of deuterium clusters with initial radius of 50-200 A irradiated by a subpicosecond laser with intensity of 10¹⁶ W/cm² is examined theoretically. We studied the conversion efficiency of laser energy to ion kinetic energy, the mean and maximum ion kinetic energy, and ion energy distribution function by a molecular dynamics model. A yield of ∼10⁵-10⁶ neutrons/J is obtainable for a peak laser intensity of 10¹⁶-10¹⁷ W/cm² and clusters with an initial radius of 200-400 A

No abstract available

[en] The inhomogeneous electron Boltzmann equation is solved for an Ar-Hg positive column direct current glow discharge with properties similar to the standard fluorescent lamp. The inhomogeneity arises from the ambipolar potential and requires the inclusion of the spatial gradient term in the Boltzmann equation. The electron kinetics is coupled to a collisional-radiative equilibrium model for various states of Ar and Hg subject to a reaction set with electron and heavy particle collisions. The axial electric field and space-charge potential are solved self-consistently. The calculated electron distribution function satisfies neither the local nor nonlocal approaches, but rather is found to be a function of both the electron energy and radial position. The radial dependence produces an energy flow from one part of the discharge to another, which results in nonuniform ultraviolet radiative power. Results are given for global properties of the discharge such as power per unit length and axial electric field, as well as spatially averaged quantities (densities, electron and gas temperatures, and emission powers) as a function of the wall temperature and the current. Extensive comparisons are presented with experimental data and previous homogeneous Boltzmann models of the discharge. The optimum current and fill pressures are determined and the general trends of varying the input parameters are established. There is general agreement between the present model and data, except that the calculated average electron density is larger than the measured values

[en] The dynamics of Xe clusters with initial radius between 10 and 100 A irradiated by an IR subpicosecond laser pulse is investigated. The evolution of the cluster is modeled with a relativistic time-dependent three-dimensional particle simulation model. The focus of this investigation is to understand the energy absorption of clusters and how the absorbed energy is distributed among the various degrees of freedom. The consequence of the initial cluster radius on the absorbed energy, average charge per atom, mean electron and ion energies, ionization, removal of electrons from the cluster, and cluster expansion was studied. The absorbed energy per cluster scales as N^5/3, and the mean electron and ion energies scale as N^1/3 and N^2/3, respectively (N is the number of atoms per cluster). A significant fraction of the absorbed energy (∼90%) is converted into kinetic energy with comparable contribution to electrons and ions. The energy balance suggests that smaller clusters are more efficient as radiators, while larger clusters are more conducive to particle acceleration. The radiation yield of clusters with initial radius 20-50 A irradiated by a laser with peak intensity 10¹⁶ W/cm² is determined to be 1%-2%