7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Progress of EUV impurity lines spectral diagnostics of highly charged Xe ions
measured in Large Helical Device
Shivam Gupta1, Tetsutarou Oishi2, Motoshi Goto1, 3, Yasuko Kawamoto1, 3, Tomoko Kawate1, 3, andIzumi Murakami1, 31National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Japan
2Department of Quantum Science and Energy Engineering, Tohoku University, Sendai, Japan
3Graduate Institute for Advanced Studies, SOKENDAI, Toki, Japane-mail (speaker): shivam.gupta@nifs.ac.jpThe study of spectral lines emitted from individual
extrinsic impurities in high-temperature tokamak devices
plays an essential role in diagnosing the fusion plasma intheir edge and core regions through various diagnostic
methods [1]. Many impurity seeding experiments havebeen conducted using Nitrogen (N2), and inert gases suchas Neon (Ne), Argon (Ar), and Krypton (Kr), to study theradiation enhancement and reduction of the particle heatload in the divertor region for the divertor detachment in
the fusion devices [2-6]. However, in large-scale fusionplasma devices such as ITER and CFETR, etc. higher
atomic Z elements (e.g. Kr and Xe) are considered to besuitable to serve as the impurity seeding element for theX-ray Crystal Spectrometer (XCS) diagnostics [7-8]. The
contribution of each charge state of the highly charged Xeions has not yet been clarified in detail in hightemperature fusion plasma, and their detailed atomic dataand collision cross-section data are required for plasma
modling purposes [9]. Therefore, the proper analysis ofsuch high Z spectra through a suitable plasma model isrelevant for international large tokamak devices, viz.
ITER, DEMO reactors, etc. [7-8].
In view of this, Extreme Ultraviolet (EUV) spectral
diagnostics of highly charged Xe ions have been
programmed for the 24th campaign of the Large Helical
Device (LHD) at the National Institute for Fusion Science(NIFS) Japan using a suitable Collisional Radiative (CR)plasma model calculation. In the present work, early CR
model calculations have been carried out for the Xe18+Xe19+ charge states for the preparation of the LHD
experiment and detailed CR model. An impurity seeding
experiment was conducted using the Xe gas puff. In theexperiment, LHD plasma was ignited using the Electron
Cyclotron Heating (ECH) system, while Negative-ionbased Neutral Beam Injection (N-NBI) #1-3 were utilized
to sustain the plasma from 3.3-7.3s. Xe gas was injected
at 4.0s, and emission spectra of highly charged Xe charge
states were measured in the EUV long (8-26nm) and EUV
short (2-9nm) wavelength regions. The detailed spectral
analysis of measured Xe-ions will be performed tovalidate the theoretical collisional data and CR model
calculations by comparing the LHD-measured spectrawith theoretical synthetic spectra.
The CR model calculation includes various populationtransfer kinetic processes among the fine structure levelsof the considered Xe-ions, such as electron impact
excitation and ionization, radiative decay, and theirreverse processes. Detailed atomic structure and collisioncalculations have been performed for the excitationenergies, oscillator strengths, wave functions, and theircross-sections for various fine structure transitions fromthe ground state and excited states to the other finestructure levels using the Flexible Atomic Code (FAC)[10]. In addition, relativistic multi-configuration DiracHartree-Fock (RMCDHF) calculations will be carried outfor the Xe18+-Xe19+ charge states using the General
Purpose Relativistic Atomic Structure Packages(GRASP2018) to confirm the reliability of the FAC
calculations [11]. Further, these calculated data will beincorporated into the CR model to solve the kinetic ratebalance equations. Theoretical synthetic spectra will begenerated through the population of the considered finestructure levels of the Xe-ions. The comparison oftheoretical spectra with the LHD-measured spectra willvalidate the atomic structure and collision data
calculations prominent for spectroscopic diagnostics offuture fusion plasma experiments in different tokamak
devices. Detailed experimental and theoretical results will
be discussed at the conference.
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