Plasma and Fusion Research

Volume 21, 2401006 (2026)

Regular Articles

Photoexcitation Spectroscopy of Highly Charged Ions for Application to Astronomy Using a Compact Electron Beam Ion Trap (EBIT) at the Synchrotron Radiation Facility SPring-8
Leo HIRATA1,2,3), Yuki AMANO2,3), Moto TOGAWA4,5), Hiroyuki A. SAKAUE6), Nobuyuki NAKAMURA3,7), Makoto SAWADA3,8), Hiromasa SUZUKI3,9), Masaki OURA10), Hiroya YAMAGUCHI1,2,3)
1)
Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
2)
Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara 252-5210, Japan
3)
RIKEN Pioneering Research Institute, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
4)
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
5)
European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany
6)
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho, Toki 509-5292, Japan
7)
Institute for Laser Science, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu 182-8585, Japan
8)
Department of Physics, Rikkyo University, 3-34-1 Nishi Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan
9)
Faculty of Engineering, University of Miyazaki, 1-1 Gakuen Kibanadai-nishi, Miyazaki 889-2192 Japan
10)
RIKEN SPring-8 Center, RIKEN, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
(Received 30 September 2025 / Accepted 2 November 2025 / Published 31 March 2026)

Abstract

In the past few decades, X-ray astronomy satellites equipped with grating spectrometers and microcalorimeters have enabled high-resolution spectroscopic observations of astrophysical objects. The need for accurate atomic data has arose as we attempt detailed analysis of the high-resolution spectra they provide. This is because current spectral models, which heavily rely on theoretical calculations, entail non-negligible uncertainties. We employ a plasma spectroscopy device called electron beam ion trap (EBIT) to experimentally obtain precise atomic data. An EBIT with a design that allows combined operation with synchrotron radiation facilities was developed based on the Heidelberg Compact EBIT and installed at ISAS/JAXA for this purpose. We conducted a spectroscopic experiment using the JAXA-EBIT at the synchrotron radiation facility SPring-8, and successfully obtained high-resolution spectra of the Lα resonance transition of Ne-like Fe16+ ions, 3C, as well as the Kα resonance transition of He-like O6+ ions. We also measured another Ne-like Fe16+ Lα resonance transition, 3G, and constrained an upper limit of the oscillator strength ratio of 3G to 3C, using our experimental results. The experimental values obtained in this study will be applied to observational studies of astrophysical objects as a part of the plasma spectral modeling.

Keywords

plasma spectroscopy, resonant photoexcitation, highly charged iron ion, electron beam ion trap (ebit), synchrotron radiation, atomic data, x-ray astronomyity

DOI: 10.1585/pfr.21.2401006

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