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Measurement of the Effective Electron Density in the SAO EBIT

Presentation #105.26 in the session Missions and Instruments - Poster Session.

Published onMay 03, 2024
Measurement of the Effective Electron Density in the SAO EBIT

Electron densities in astrophysical sources can be determined spectroscopically using sensitive line ratios. However, laboratory tests are required to verify the accuracy of the atomic data and provide realistic uncertainties. The electron beam ion trap (EBIT) at the Smithsonian Astrophysical Observatory is ideally suited to carry out such calibration studies, provided the electron density is well-understood. In an EBIT, trapped ions extend beyond the dense electron beam and can experience a lower effective electron density. We describe an experimental setup used to determine the effective electron density by measuring the spatial distribution of the electron beam and ion cloud. An optical setup consisting of two lenses, a narrow band filter, and a CCD camera was used to image emission from a metastable transition in Ar13+, while an X-ray pinhole and CCD camera were used to image X-rays, primarily from Ar16+ and Ar17+. Measurements were used to estimate the ion cloud and electron beam spatial distribution from which an effective electron density of 1.77 x 1010 cm−3 was derived. This is about an order of magnitude less than predicted from the geometry of the electron beam alone.

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