[en] A method of synthesizing KMnF₃, KFeF₃, CoF₃ and KNiF₃ crystals is described for investigating them by the Moessbauer method on the Fe⁵⁷ isotope. Neel and Debye temperatures found for these crystals are given. The X-ray diffraction analysis of samples with a Fe⁵⁷ impurity confirms their single-phase character. For pure KMnF₃, KFeF₃, KCoF₃ and KNiF₃ the lattice constants are 4.184+-0.003, 4.116+-0.004, 4.065+-0.004 and 4.011+-0.002 A⁰, respectively. The Moessbauer spectra (MS) of all the absorbers at T=295 K present a single line of the width GAMMA = 0.4-0.6 mm/s with an isomeric shift sigma = +1.48+-0.02 mm/s relative to the source of Co⁵⁷(Cr). Line splitting in MS makes it possible to determine the temperature of magnetic transformation: Curie temperature for ferro- and ferrimagnetics and Neel temperature for antiferromagnetics. The dependence is presented of the number of γ-quanta passed through the KCoF₃-Fe⁵⁷ absorber on temperature at the source fixed velocity. The temperature of a drastic increase in the counting rate of γ-quanta corresponds to transformation of a crystal into a magneto-ordered state

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[en] The neutron beams generated at accelerators using nuclear reactions with well-known parameters are widely used in neutron physics and in many practical applications. This paper is devoted to the formation of a thermal neutron beam and the measurement of its intensity and spatial distribution at an angle of 0° to the beam axis using an activation method and an ionization chamber with a solid boron radiator KNT-10 that is not sensitive to γ-radiation. The nuclear reaction of ⁷Li(p,n) on metallic lithium installed in a cooled target device of the Tandetron accelerator was used as a neutron source.

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[en] It is shown that, at a sufficiently high current growth rate, the initial stage of implosion of a wire array is significantly affected by the radial electric fields. Due to the specific electrode configuration of wire arrays, the magnitude of the oppositely directed radial electric fields in different wire segments can reach 5 MV/cm. It is found that the process of plasma formation proceeds in different ways in segments with oppositely directed initial radial electric fields. The influence of this effect (the so-called 'polarity effect') on the implosion of cylindrical tungsten wire arrays in the Angara-5-1 facility becomes significant when the load voltage grows at a sufficiently high rate

[en] Results are presented from experimental studies of the anode plasma dynamics and measurements of the ion flux ejected along the axis of a high-current Z-pinch. Pinch discharges were formed by the implosion of tungsten wire arrays in the Angara-5-1 facility. It is shown that the ion energy spectrum depends on the mass and configuration of wire arrays, as well as on the diameter of the anode aperture. The shape of the ion spectrum indicates that the plasma propagates in the form of a compact plasmoid. Shadow and X-ray images of the plasma show that the axial velocity of the plasma outflowing through the anode aperture is comparable with the velocity of radial plasma compression and, for tungsten ions, can reach a value corresponding to an energy of 100 keV. The experimental data indicate that the ion energy spectrum mainly forms due to the electrodynamical acceleration of the plasma and cumulative jets. A possible mechanism for the production of compact plasma formations in the course of electrodynamic plasma acceleration is discussed.

[en] Results are presented from experimental studies of the implosion of twisted nested arrays in which the wires of the outer and inner arrays are twisted about the array axis in opposite directions (clockwise and counterclockwise). Experiments with twisted arrays were carried out at the Angara-5-1 facility at currents of up to 4 MA. The currents through the arrays were switched either simultaneously or the current pulse through the outer array was delayed by 10–15 ns with the help of an anode spark gap. It is shown that, in such arrays, the currents flow along the inclined wires and, accordingly, there are both the azimuthal and axial components of the discharge current. The process of plasma implosion in twisted arrays depends substantially on the value of the axial (longitudinal) magnetic field generated inside the array by the azimuthal currents. Two-dimensional simulations of the magnetic field in twisted nested arrays were performed in the (r, z) geometry with allowance for the skin effect in the discharge electrodes. It is shown that, depending on the geometry of the discharge electrodes, different configurations of the magnetic field can be implemented inside twisted nested arrays. The calculated magnetic configurations are compared with the results of measurements of the magnetic field inside such arrays. It is shown that the configuration of the axial magnetic field inside a twisted nested array depends substantially on the distribution of the azimuthal currents between the inner and outer arrays.

[en] Results are presented from experimental studies of hard X-ray (HXR) emission in the photon energy range above 20 keV from dense radiating Z-pinch plasmas. The work is aimed at revealing the nature of fast-electron (electron beam) generation during the implosion of cylindrical and conical wire arrays in the Angara-5-1 facility at currents of up to 3 MA. It is found that the plasma implosion zippering caused by the inclination of wires affects the parameters of the HXR pulse emitted during the implosion of a conical array. It is shown that HXR emission correlates well with the decay of the plasma column near the cathode in the stagnation phase. HXR images of the pinch are produced by the bremsstrahlung of fast electrons generated during plasma column decay and interacting with plasma ions and the anode target. It is found that the use of conical arrays makes it possible to control the direction of plasma implosion zippering and the spatiotemporal and energy parameters of the pinch X-ray emission, in particular the X-ray yield. For wire array with diameters of 12 mm and linear masses of 200-400 μg/cm, the current of the fast electron beam is 20 kA and its energy is 60 J, which is about 1/500 of the energy of the main soft X-ray pulse.