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We report here our results on the formation of a plasma configuration with the generic name of compact toroid (CT). A method of compact toroid formation to confine, heat and compress a plasma is investigated. Formation of a compact torus using an additional toroidal magnetic field helps to increase the plasma current to a maintainable level of the original magnetic field. We design the Compact Toroid Challenge (CTC) experiment in order to improve the magnetic flux trapping during field reversal in the formation of a compact toroid. The level of the magnetic field immersed in the plasma about 70% of the primary field is achieved. The CTC device and scheme of high level capturing of magnetic flux are presented. V C 2014 AIP Publishing LLC.

Measurement results for temperature dependences of kinematic viscosity in Bi-Pb melts are presented. Measurements were carried out in the temperature range between liquidus and 1400 K. The distinctive feature of experiments was their performance at heating after sample melting and further cooling. On the experimental temperature dependences of kinematic viscosity the values of viscosity at fixed temperature and activation energy of viscous flow have been calculated. Special attention was paid to non-coincidence of the curves obtained at heating and cooling. The specified anomaly is explained by the concept of metastable microcoherence of the studied melts.

Various ways of initiating cathode plasma for producing high-current densities of negative ions were tried at the P. N. Lebedev Physical Institute. The first was prepulse induced electrical breakdown on the surface of a dielectric inserted between two metallic parts of a cathode. A second method was surface discharge of a perforated dielectric sleeve on a metallic cathode rod, which yielded acceptable plasma parameters for larger prepulse voltages than in the first case. A circuit was developed and tested to supply an externally applied prepulse with changeable parameters. The third method employed laser illumination of a cathode dielectric surface to initiate cathode plasma. No prepulse was used in this case and nearly the same current densities of negative hydrogen ions were obtained as with the first method of plasma initiation. A new more widely applicable way of cathode plasma initiation was proposed recently and studied experimentally. This method allows one to produce negative ions of various chemical elements in high-current pulsed diodes. It utilizes cathode bombardment by positive ions extracted from near-anode plasma injected at the outer surface of the anode and which penetrates partially through anode holes into the diode. Plasma parameters can be easily varied by changing plasma gun voltage and time delay between plasma gun pulse and diode voltage pulse. Current densities of up to 30 A/cm2 of H− and about 1 A/cm2 of C−, 0.3 A/cm2 of F− and 0.1 A/cm2 of I− and Pb− were recorded using this last method of cathode plasma production. The merits and disadvantages of all methods of cathode plasma production are discussed.

Experimental studies of cathode plasma formation to generate high-power negative ion beams of various elements in a coaxial magnetically insulated pulsed diode are presented. The vacuum spark discharge outside the anode was used to facilitate cathode plasma formation with high content of H-, C-, F-, I-and Pb-ions. The main mechanism responsible for cathode plasma formation is cathode bombardment by positive ions accelerated from anode plasma by the main pulse accelerator voltage.