Characteristics of high-power radiating imploding discharge with cold start

A qualitative model of the dynamics of a multiterawatt radiating Z-pinch with cold start and high rate of current rise is proposed. The model is used to analyze discharges with currents I ～ 2–5 MA (with dI/dt > 10¹³ A/s) through uniform or structured plasma-producing loads, including wire arrays. The most important consequence of cold start is that spatially nonuniform plasma production is prolonged to almost the entire current rise time. Under these conditions, the Ampére force begins to play a dominant role in the plasma dynamics before the plasma-producing load is completely transformed into an accelerated plasma. The results of computations of wire-array vaporization are presented. A formula is proposed for estimating the highest attainable velocity of plasma flow into a heterogeneous liner driven by the Ampére force. It is shown that local imbalance between radial motion of the produced plasma and supply of the plasma-producing substance to be ionized leads to axially nonuniform breakthrough of magnetic flux into the liner, which precedes plasma collapse. The magnetic-flux breakthrough gives rise to a chaotic azimuthal-axial plasma structure consisting of radial plasma jets of relatively small diameter, which is called a radial plasma rainstorm. The breaking-through azimuthal magnetic flux obstructs further current flow in the breakthrough region. Analyses of Z-pinch implosion based on the theory of Rayleigh-Taylor instability or the snowplow model are incorrect under the plasma-rainstorm conditions. The processes taking place in a stagnant Z-pinch include conversion of the energy carried by the current-generated magnetic field into turbulent MHD flow of the ion component of the plasma, its convective mixing with magnetic field, heating, energy transfer from ions to electrons, and emission from the plasma. Under typical experimental conditions, emission plays a key role in the energy balance in an imploding pinch. Z-pinch is modeled by an electric-circuit component that has a time-dependent nonlinear impedance and consumes the magnetic energy supplied by a generator through a magnetically insulated transmission line (MITL). The peak power reached in the circuit is comparable to the peak soft X-ray power output emitted by the pinch in terms of magnitude and timing. Optimum matching conditions are formulated for the generator-MITL-pinch circuit.     

Expansion of explosion products of silver azide

A new method for studying the kinetics of the expansion of explosion products based on measuring the time elapsed from explosion initiation to the short-circuiting of the discharge gap by the products was proposed. It was revealed that, at the initial stage of expansion of the silver azide explosion products, they move with uniform acceleration, a behavior suggestive that, during this period, the exothermic reaction 2N₃ → 3N₂ occurs.     

Ultrasoft x-ray emission spectra of the components in complete titanium nitrides

Results are given for a study of the TiL, TiL, and NK x-ray emission bands in TiC _1–x N _x compounds (x from 0.038 to 0.930). These spectra served as the basis for a discussion of the structure of the energy bands of TiC–TiN solid solutions and the evaluation of the validity of various theoretical models. The possibility of determining the composition of solid carbonitride alloys by analysis of the intensity of the x-ray emission bands was examined.Institute of Metal Physics, Urals Branch, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 6, pp. 75–78, November–December, 1989.     

Calculation of Absorption Intensities of Cr3+ Ion Pair Lines in Ruby

The calculation of relative intensities of the optical absorption lines of the fourth order pair of Cr³⁺ ions in ruby has been performed assuming the electro-dipole character of the transitions.     

Complexation of Scandium with Oxabis(ethylenenitrilo)tetramethylenephosphonic Acid and Applicability of Its 44Sc-Labelled Analogue as Bone-Seeking Agent

Russian Journal of General Chemistry - The regularities of complexation of scandium with oxabis(ethylenenitrilo)tetramethylenephosphonic acid (OBEP), which is actively used nowadays in the clinical...     

Silver/polystyrene-coated hollow glass waveguides for the transmission of terahertz radiation

We have applied techniques developed for IR waveguides to fabricate Ag/polystyrene (PS) -coated hollow glass waveguides (HGWs) for transmission of terahertz radiation. A loss of 0.95 dB/m at 119 microm (2.5 THz) was obtained for a 2 mm bore, 90 cm long Ag/PS HGW. We found that TE modes are supported in HGWs with thin PS films, while hybrid (HE) modes dominate when PS film thickness increases. The lowest losses are obtained for the thicker PS films and the propagation of the HE modes.     

Laser-Synchrotron Facility of the National Research Centre “Kurchatov Institute”

Crystallography Reports - The laser-synchrotron facility (LSF) of the National Research Centre “Kurchatov Institute” (NRC KI) is a unique research complex that combines unprecedented...     

Wire metamaterial based on semiconductor matrices

In this Letter, we have presented a new approach for the fabrication of nanowire media (wire metamaterials) by electrochemical methods. A^IIIB^V porous matrices (a host medium) were prepared by anodic electrochemical etching of industrial substrates. The host medium has been filled via electrochemical deposition with a metal and by means of annealing process. We have shown that this technique can be used to fabricate a nanowire medium with unique parameters (such as aspect ratio, high electric permittivity and strong χ⁽³⁾ nonlinearity near the fundamental absorption edge of the host media). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)