Spectroscopic investigations of a dielectric-surface-discharge plasma source

Abstract

Spectroscopic investigations of the properties of a plasma produced by a flashboard plasma source, commonly used in pulsed plasma experiments, are presented. The plasma is used to prefill a planar 0.4-µs-conduction time plasma opening switch (POS). A novel gas-doping technique and a secondary surface flashover plasma source are used to locally dope the plasma with gaseous and solid materials, respectively, allowing for spatiallyresolved measurements. The electron density, temperature, and plasma composition are determined from spectral line intensities and line profiles. Detailed collisional-radiative modeling is used to analyze the observed line intensities. The propagation velocity and divergence angle of various ions are determined from time-of-flight measurements and Doppler broadening of spectral lines, respectively. This allows for distinguishing the secondary plasma ejected from the POS electrodes from the plasma of the flashboard source.

Electron density evolution during a fast, non-diffusive propagation of a magnetic field in a multi-ion-species plasma

“…The current generating the magnetic field is applied 1.1 ls after the application of the flashboard plasma source. By this time, the electron density (n e ) and temperature (T e ) in the middle of the interelectrode gap are found to be, 34 respectively, n e $ 3 Â 10 14 cm À3 and T e $ 6.5 eV.…”

“…However, here, the initial T e is 10 eV, 34 and thus I 3d =I 3p depends both on T e and n e . Thus, additional data are required for the diagnostics.…”

“…The inferred ion dynamics, together with the known plasma composition and initial ion velocity distribution, 34 allow for deriving the electron density evolution and examining whether the potential hill assumption is consistent with the measured density. If the ionization rate of the plasma constituents is negligible, then the density evolution of each ion species in the plasma is determined by the change in the velocity distribution of that ion species.…”

“…The equations that describe the change of the density as a function of the ion position in the potential hill are given in the Appendix. The plasma composition is taken from a previous study, 34 but scaled here by a factor of 0.7 to account for minor modifications in the experimental set-up. Thus, the initial ion density are: n p ¼ 3:5 Â 10 13 cm À3 , n CII ¼ 9:1 Â 10 12 cm À3 , n CIII ¼ 1:5 Â 10 13 cm À3 , n CIV ¼ 4: 9 FIG.…”

Is There a High‐Energy Particle Population in the Quiet Solar Corona?

“…Calculations of the level populations and line intensities expected from non-Maxwellian plasmas were performed with the collisional-radiative (CR) code NOMAD (Ralchenko & Maron 2001). This code allows modeling of plasma population kinetics for an arbitrary electron energy distribution function and was intensively used in simulations of emission from low-and medium-density plasmas (see, e.g., Arad et al 2000;Gregorian et al 2005).…”