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Laboratory measurements of Fe IX EUV line emission using EBIT-I

Presentation #110.02 in the session Data Analysis Techniques Posters.

Published onSep 18, 2023
Laboratory measurements of Fe IX EUV line emission using EBIT-I

The Ar-like Fe IX 241.739/244.909 Å intensity ratio is predicted to be one of the best extreme ultraviolet (EUV) density diagnostics for the 106 K solar corona. This intensity ratio varies by over three orders of magnitude from densities of 108 to 1012 cm−3. Despite this, the diagnostic is not commonly used in part because previous observations by Orbiting Solar Observatory (OSO) 5, OSO 7, and Skylab, showed that the inferred electron densities differ significantly from those obtained from other ions. Uncertainties in the underlying atomic data have been proposed as one possible reason for the disagreement. Density diagnostics can be very sensitive to uncertainties in the atomic data because they depend on many factors, such as collisional excitation and de-excitation rates, radiative transition rates, and cascade contributions from higher energy levels. Additionally, line blends, including those from other ions, can impact the accuracy of density diagnostics. In order to benchmark the density sensitive line ratio of the Fe IX line pair, we have measured the EUV line emission from Fe VII-Fe X in the wavelength range 238 to 258 Å at the Lawrence Livermore National Laboratory electron beam ion trap (EBIT-I). Here we report a new line survey of Fe M-shell emission in this wavelength range and the implications for the 241.739/244.909 Å density diagnostic.

This work was supported by NASA H-TIDeS Grant No. 80NSSC20K0916 and was performed in part under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

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