E. Velikhov

Materials processing by high-repetition-rate pulsed excimer and carbon dioxide lasers

Recently created pulsed gas lasers with high pulse repetition rate produce radiation in the IR [ V. Yu. Baranov , in Molecular Gas Lasers. Physics Applications, VelikhovE. P., Ed. ( Mir, Moscow, 1981), pp. 252– 255] and the UV ( V. Yu. Baranov , in Proceedings, International Conference on Lasers, 14–18 Dec. 1981, pp. 968– 974) regions of the spectrum. These lasers are widely used in research on the selective excitation of matter. This field of study includes laser isotope separation { G. I. Abdushelashvili , Kvantovaya Elektron. (Moscow)9, 743 ( 1982) [ Sov. J. Quantum Electron.12, 459 ( 1982)]} and laser-induced chemical reactions [ V. Yu. Baranov , Preprint IAE 3693/13 ( Moscow, 1982)]. But there are few publications dealing with uses of high-repetition-rate lasers for materials processing, although this problem undoubtedly is of considerable scientific interest.

Multiwatt optically pumped ammonia laser operation in the 12–13 μm

Design and operating caracteristics of high pulse repetition rate NH3 laser producing up to 20 W of average output power are described. The NH3 laser, operating in the 12–13 μm region was optically pumped with a high pulse repetition rate TEA CO2 laser. Dependences of the NH3 laser output on the pump energy, ammonia and buffer gas pressures and pulse repetition rate have been studied. The conversion efficiency of up to 16% has been received.

Magnetorotational instability in electrically driven flow of liquid metal : Spectral analysis of global modes

The spectral magnetohydrodynamics stability of liquid metal differentially rotating in transverse magnetic field is studied numerically by solving the eigenvalue problem with rigid-wall boundary conditions. The equilibrium velocity profile used in calculations corresponds to the electrically driven flow in circular channel with the rotation law Ω(r)∝1∕r2. This type of flow profile is planned to be used in new experimental devices to test the magnetorotational instability (MRI) in the laboratory. Our analysis includes calculations of the eigenfrequency spectra for both axisymmetric (with azimuthal wavenumber m=0) and nonaxisymmetric (m≠0) modes. It is shown that for certain parameters the flow is unstable with respect to MRI with the fastest growth rate corresponding to the axisymmetric mode. For other parameters, the axisymmetric MRI modes can be suppressed and the instability develops only for modes with m≠0.

Magnetic field distribution in the plasma flow generated by a plasma focus discharge

The magnetic field in the plasma jet propagating from the plasma pinch region along the axis of the chamber in a megajoule PF-3 plasma focus facility is studied. The dynamics of plasma with a trapped magnetic flow is analyzed. The spatial sizes of the plasma jet region in which the magnetic field concentrates are determined in the radial and axial directions. The magnetic field configuration in the plasma jet is investigated: the radial distribution of the azimuthal component of the magnetic field inside the jet is determined. It is shown that the magnetic induction vector at a given point in space can change its direction during the plasma flight. Conclusions regarding the symmetry of the plasma flow propagation relative to the chamber axis are drawn.

The application of a high pulse repetition rate CO2 laser with high average power for isotope separation by molecular dissociation in a strong IR field

Considering a SF6 molecule we demonstrate feasibility of using high pulse repetition rate CO2 laser for isotope separation by selective molecular dissociation in a strong IR field. Dependences of dissociation efficiency as well as separation selectivity on pulse repetition rate up to 150 Hz are investigated. The inherent thermal effects are discussed.

Electromagnetic sounding of the Kola Peninsula with a powerful extremely low frequency source

Experiment on electromagnetic sounding of the Kola Peninsula using unique mobile measuring complex of the low-frequency sounding was conducted, allowing to investigate a geoelectric section with a depth of several kilometers on distances up to 100 km from the stationary transmitting aerial. Excess on the order of amplitudes of the vertical component above the horizontal at all frequencies of sounding was registered in a number of points of measurements. This feature managed to be explained quantitatively by circulation of current on regional faults with the closure of current through the sea—before unknown galvanic coastal effect. Interpretation of the results of modeling and neural network solving of inverse problem essentially specifies the fault tectonics of the central part of the Kola Peninsula. Anomaly remote from the observation profile was found out—local pinch of a crustal conductive layer consisting of graphitized rocks and associated with the zone of overthrust.

KTM Experimental Complex Project Status

Abstract A review of KTM experimental complex project status, which is aimed the creation of a Kazakhstani spherical tokamak for study and tests materials and components of future fusion reactors. Revised basic parameters of the KTM facility and ground of the changes taking into account new plasma core geometry, new design of vacuum chamber and modified magnetic system, transport sluice and movable divertor devices, and additional RF-heating system are presented here.

Project ‘Baikal’ – testing the scheme for electric pulse generation

The scheme of a multi-objective installation ‘Baikal’, a multi-megajoule source of X-ray emission with a temperature of 250–300 eV and a power of 500–1000 TW, is described in this article. The Project of the ‘Baikal’ installation is based on an inductive energy store, which in the process of step-by-step energy transmission with increasing power generates an electric pulse with parameters required for compression of liners. Electric parameters of the ‘Baikal’ installation are: current −50 MA, voltage 8–10 MV, pulse duration −150 ns, pulse energy 30 MJ. An installation ‘MOL’ is intended for testing the scheme of one of ‘Baikal’ modules. It consists of an inductive store IN-1 with accumulated energy of 12,5 MJ, capacitor banks, a magnetic amplifier, a magnetic compressor with a capacitor bank for generation of initial magnetic flow, a plasma opening switch (POS) and a load simulator.

The Kovdor-2015 experiment: study of the parameters of a conductive layer of dilatancy–diffusion nature (DD Layer) in the Archaean crystalline basement of the Baltic Shield

This paper addresses the Kovdor-2015 Experiment involving frequency electromagnetic soundings of the Archaean basement of the Earth’s crust in the southwestern part of the Kola Peninsula. Eleven soundings were carried out using two transmitting arrangements, 85 km apart. Each arrangement consisted of two mutually orthogonal grounded electric dipoles of 1.5 km long. The distances between the source and the receiver were 25 and 50 km. Interpretation of the results took into account the influence of displacement currents and static distortions. It is found that there is an intermediate conductive layer of the dilatancy–diffusion nature (DD layer) with a longitudinal conductivity of about one siemens at depths ranging from 1.5–2 to 5–7 km. The results are interpreted in the terms of geodynamics.

Magneto-rotational instability in the accreting envelope of a protostar and the formation of the large-scale magnetic field

We investigate the role of the magnetic field in the collapse of a gas-dust cloud into a massive gravitating object. Observations of one such object (G31.41) indicate that the magnetic field has an hourglass shape oriented along the rotation axis of the matter, due to the freezing-in of the magnetic-field lines in the accreting matter. It is believed that accretion in stellar disks is associated with the transport of angular momentum from the center to the periphery, which could be initiated by large-scale vortex structures arising in the presence of unstable rotational flows of matter. The numerical simulations have established that the equilibrium configuration of a gas-dust disk rotating in a spherically symmetrical gravitational potential is subject to the development of strong instability in the presence of a weak magnetic field. It is shown that the development of instability leads to a transport of angular momentum to the disk periphery by large-scale vortex structures, together with the accretion of matter onto the gravitating object. The magnetic-field lines near the equator take on a chaotic character, but an hourglass configuration is observed near the rotation axis, in agreement with observations.