Broadening of the neutral helium 492 nm line in a corona discharge: code comparisons and data fitting

International audiencePassive plasma spectroscopy is a well-established non-intrusive diagnostic technique.Depending on the emitter and its environment which determine the dominant interactions and effectsgoverning 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 governingthe emission line profiles. This is required for line shape code developers to continuously corrector improve them to increase their accuracy when applied for diagnostics. This is exactly the aimexpected from code–code and code–data comparisons. In this context, the He I 492 nm line emitted ina helium corona discharge at room temperature represents an ideal case since its profile results fromseveral broadening mechanisms: Stark, Doppler, resonance, and van der Waals. The importance ofeach broadening mechanism depends on the plasma parameters. Here the profiles of the He I 492 nmin 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 experimentalspectrum from a helium corona discharge at atmospheric pressure, are presented