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内容記述 |
This study presents a spectroscopic investigation of Kr24+ ion, generated via a krypton impurity seeding experiment in the Large Helical Device, aimed at supporting Extreme Ultraviolet (EUV) diagnostics of high-temperature fusion plasma. EUV spectral lines corresponding to fine-structure transitions among the 2p63s2, 2p63s3p, 2p63s3d, and 2p63p2 configurations were observed in the 12–25 nm wavelength range. To systematically analyze the measured emission lines, extensive relativistic atomic structure calculations were carried out over a broad configuration space, spanning more than 40 configurations, including core-excited and correlation-dominated states up to n ≤ 7 and ℓ ≤ 4. Bound-state wave functions were obtained using the relativistic many-body perturbation theory and configuration interaction method, implemented via the Flexible Atomic Code. Parallel calculations based on the relativistic multiconfiguration Dirac-Hartree-Fock method with configuration interaction were performed using the GRASP-2018 code to ensure numerical consistency. This article presents fine-structure-resolved excitation energies and transition parameters, including oscillator strengths and transition probabilities, for the relevant spectroscopic configurations up to 3ℓ. Moreover, electron impact excitation and ionization cross-sections from the ground state (2p63s2 1S0) as well as from selected excited states to higher-lying levels were calculated using the relativistic distorted wave method from the respective thresholds over a wide energy range. The corresponding Maxwellian averaged rate coefficients for excitation, de-excitation, ionization, and three-body recombination were evaluated over fusion-relevant electron temperatures. The results are presented for the prominent spectroscopic transitions up to 3ℓ. These complete atomic and electron-collision datasets were incorporated into a suitable collisional-radiative model, accounting for the dominant population and depopulation processes, including electron impact excitation, de-excitation, ionization, radiative decay, and three-body recombination. The theoretically modeled EUV spectrum, calculated at ne=5.5 × 1019 m-3 and Te=578 eV, shows good agreement with experimental observations, validating the accuracy of the calculated atomic structure, and electron-collision parameters. The resulting atomic dataset and modeling framework enable detailed spectral analysis of highly charged Kr24+ ion under magnetically confined fusion plasma conditions. |
