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

Determination of the Li I 4d–4f Energy Separation Using Active Spectroscopy

An accurate knowledge of the Li i 4d–4f energy separation is essential for the determination of electric fields, as is pursued using several modern diagnostic techniques. However, there is a rather large spread in the values of this quantity in the available data sources. We have measured the Li i 4d–4f energy separation using a technique that combines laser-induced-fluorescence with the utilization of collisional excitations. The plasma used for these measurements is laser-produced, which allows for selection of an electron-density range for which line shifts due to the plasma microfields are sufficiently small. An observation of the forbidden 2p–4f line provides the information on the microfields that allows for accounting for the Stark-shifts and evaluating the 4d–4f energy separation in the field-free limit. A comparison of the measured value with a few previous measurements allows for resolving the uncertainties in this quantity. 1

Recent advances in Stark line broadening calculations and their applications to precise spectroscopy of pulsed plasmas

A new method for the calculation of the spectral line broadening in plasma has been developed and implemented. The main idea of the method is to numerically simulate the motion of the plasma particles, both ions and electrons, and use the resulting time-dependent field to evaluate the emitter oscillating function, the Fourier transform of which provides the spectral line shape. We applied this method to the analysis of dipole-forbidden line shapes used for the determination of plasma properties