Electric fields in plasmas under pulsed currents

Electric fields in a plasma that conducts a high-current pulse are measured as a function of time and space. The experiment is performed using a coaxial configuration, in which a current rising to 160 kA in 100 ns is conducted through a plasma that prefills the region between two coaxial electrodes. The electric field is determined using laser spectroscopy and line-shape analysis. Plasma doping allows for 3D spatially resolved measurements. The measured peak magnitude and propagation velocity of the electric field is found to match those of the Hall electric field, inferred from the magnetic-field front propagation measured previously.Comment: 13 pages, 13 figures, submitted to PR

“Electron impact ionization of helium isoelectronic systems"

We show that the criticism [Eur. Phys. J. D 49, 167 (2008)] of our empirical formula for electron-impact ionization of atomic ions [J. Phys B. 33, 5025 (2000)] is unjustified

Use of laser spectroscopy for high-accuracy investigations of relatively-dilute pulsed plasmas with nanosecond time resolution

In this report we describe the development of new approaches to measure the electric field and properties of relatively dilute plasmas under high-power pulses at the nanosecond time scale. These approaches are based on high-resolution laser spectroscopy. The study is carried out in a coaxial-pulsed-plasma configuration. The plasma was doped with a laser-produced lithium beam, followed by pumping of a selected transition in LiI using a tunable dye laser. This setup enables to perform spatially resolved sub-mm measurements of the electric field properties and the plasma parameters. For the first time, line-shape diagnostics with a sub-microsecond resolution was successfully applied to low-density plasma, down to 10 13 cm-3

High-resolution spectroscopic X-ray diagnostics for studying the ion kinetic energy and plasma properties in a pinch at stagnation,” Dig

Doubly-curved-crystal spectroscopic systems are used to obtain time-resolved measurements of Ne K emission from the stagnating plasma in a Ne-puff Z-pinch experiment. These systems, with a spectral resolving power of ≅ 6700 (only limited by the crystal Rocking curve) and simultaneous z-imaging with a resolution ≅ 0.1 mm, are used to obtain the time history of the ion kinetic energy at stagnation from the line profiles of Lyα satellites, which were verified to be optically thin. The measurements allowed for tracking the ion energy throughout the entire K-emission period. It was found that the ions lose most of their kinetic energy during the Kemission period, i.e. before the electrons cool down enough to terminate the K-emission, and before the ions recombine to Li-like charge state. Also in this study, the profile of the optically thin intercombination line was used to investigate the velocities of the He-like ions. Together with the determination of the electron density from satellite ratios, absolute line and continuum intensities, time resolved observation of the plasma size, and collisional-radiative and radiation-transport calculations, these data are used to study the various contributions to the energy deposition and energy losses of the plasma at stagnation. I