Abstract
Passive plasma spectroscopy is a well-established non-intrusive diagnostic technique. Depending on the emitter and its environment which determine the dominant interactions and effects governing emission line shapes, passive spectroscopy allows the determination of electron densities, emitter and perturber temperatures, as well as other quantities like relative abundances. However, using spectroscopy requires appropriate line shape codes retaining all the physical effects governing the emission line profiles. This is required for line shape code developers to continuously correct or improve them to increase their accuracy when applied for diagnostics. This is exactly the aim expected from code–code and code–data comparisons. In this context, the He i 492 nm line emitted in a helium corona discharge at room temperature represents an ideal case since its profile results from several broadening mechanisms: Stark, Doppler, resonance, and van der Waals. The importance of each broadening mechanism depends on the plasma parameters. Here the profiles of the He i 492 nm in a helium plasma computed by various codes are compared for a selected set of plasma parameters. In addition, preliminary results related to plasma parameter determination using an experimental spectrum from a helium corona discharge at atmospheric pressure, are presented.
Highlights
There are a number of diagnostic techniques allowing the characterization of plasmas, i.e., inferring their electron densities and temperatures, the temperatures of the other constituents, as well as other quantities like the relative abundances
As it is based on them, plasma spectroscopy needs appropriate line shape codes retaining all the physical effects governing the emission line profiles
Resonance and van der Waals broadenings [15], which are due to collisions between neutrals, can be represented by Lorentzian shapes whose full width at half maximum (FWHM) depend on the ratio (P/T) as follows: ∆λres ∝ ( P/T ) and ∆λvdW ∝ TP0.7, where P and T are respectively the pressure and the neutral temperature
Summary
There are a number of diagnostic techniques allowing the characterization of plasmas, i.e., inferring their electron densities and temperatures, the temperatures of the other constituents (emitters and ions), as well as other quantities like the relative abundances. Atoms 2018, 6, 19 compared against each other through well identified cases and against experimental data—contribute to the achievement of such an aim The He I 492 nm line emitted in a helium corona discharge at room temperature represents a rather unique case since its profile results from several broadening mechanisms whose relative importance depends on the plasma parameters. In such plasmas created by corona discharges in helium, a small amount of hydrogen is introduced for spectroscopic diagnostics like those based on the hydrogen Balmer-β line spectra, which is a subject of a separate paper in this issue [5]. The second part of this paper deals with preliminary comparisons with some experimental spectra of the same line measured in a corona discharge in helium
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