Dynamic positive column in long-gap barrier discharges

A simple analytical model of the barrier discharge in a long gap between opposing plane electrodes is developed. It is shown that the plasma density becomes uniform over large part of the gap in the course of the discharge development, so that one can speak of a formation of a dynamic positive column. The column completely controls the dynamics of the barrier discharge and determines such characteristics as the discharge current, discharge duration, light output, etc. Using the proposed model, all discharge parameters can be easily evaluatedComment: 7 pages, 8 figures; submitted to the Journal of Applied Physic

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ ГИДРОДИНАМИКИ ПУЗЫРЬКОВОГО РЕЖИМА ПРИ ДОННОЙ ПРОДУВКЕ ПЕЧИ-КОВША. СООБЩЕНИЕ III

Formation and movement of gas bubbles in the melt affect the heat interchange and the kinetics of chemical transformations in the course of copper fire refining in a ladle-furnace. The present mathematical model considers changing the bubble speed and volume and surface of moving gas bubble through the melt height. Существенное влияние на теплообмен и кинетику химических превращений при проведении огневого рафинирования меди в печи-ковше оказывают формирование и движение газовых пузырей в расплаве. В представленной математической модели рассмотрено изменение скорости пузыря, а также объема и поверхности движущегося газового пузыря по высоте расплава

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

A record fuel hot-spot pressure P[subscript hs] = 56±7  Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium–tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility, these implosions achieved a Lawson parameter ∼60% of the value required for ignition [A. Bose et al., Phys. Rev. E 93, LM15119ER (2016)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is approximately 40% lower. Three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance.United States. Department of Energy (DE-NA0001944

Electron avalanche sliding along a dielectric surface

Abstract We consider the dynamics of an electron avalanche propagating along a dielectric surface in a channel wherein the Townsend breakdown condition does not hold. We show that when the angle θ between the electric field and the channel wall is less than some critical value θ cr , the electron avalanche grows. The function θ cr = θ cr (E) is found by kinetic Monte-Carlo simulations for a mixture of Xe and Ne gasses

Polar drive on OMEGA

High-convergence polar-drive experiments are being conducted on OMEGA [T. R. Boehly et al., Opt. Commum. 133, 495 (1997)] using triple-picket laser pulses. The goal of OMEGA experiments is to validate modeling of oblique laser deposition, heat conduction in the presence of nonradial thermal gradients in the corona, and implosion energetics in the presence of laser–plasma interactions such as crossed-beam energy transfer. Simulated shock velocities near the equator, where the beams are obliquely incident, are within 5% of experimentally inferred values in warm plastic shells, well within the required accuracy for ignition. High, near-one-dimensional areal density is obtained in warm-plastic-shell implosions. Simulated backlit images of the compressing core are in good agreement with measured images. Outstanding questions that will be addressed in the future relate to the role of cross-beam transfer in polar drive irradiation and increasing the energy coupled into the target by decreasing beam obliquity