Investigation of Highly Charged Xe Ions Measured in Xe
Puffing Experiment at Large Helical Device Through Detailed
Atomic Structure and Electron-Ion Collision Calculations
Shivam Gupta1, Tetsutarou Oishi2, Chihiro Suzuki1, Motoshi Goto1, 3, Yasuko Kawamoto1, 3,Tomoko Kawate1,3, and Izumi Murakami1, 31National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Japan2

Department of Quantum Science and Energy Engineering, Tohoku University, Sendai, Japan
3Graduate Institute for Advanced Studies, SOKENDAI, Toki, Japan
https://unit.nifs.ac.jp/research/theme/unit04?paper=unit04The study of spectral lines emitted from individual extrinsic impurities in high-temperature
tokamak devices plays an essential role in diagnosing the fusion plasma in their edge andcore regions through various diagnostic methods [1]. In large-scale fusion plasma devices
such as ITER and CFETR, etc. higher atomic Z elements (e.g. Kr and Xe) are considered tobe suitable to serve as the impurity seeding element for the X-ray Crystal Spectrometer(XCS) diagnostics [2]. The contribution of each charge state of the highly charged Xe ionshas not yet been clarified in detail in high-temperature fusion plasma, and their detailed
atomic data and collision cross-section data are required for plasma modling purposes.
In view of this, Extreme Ultraviolet (EUV) spectral diagnostics of highly charged Xe ionswere programmed for the 24th campaign of the Large Helical Device (LHD). In the presentwork, early Collisional-Radiative (CR) model calculations were carried out for the Xe25+
charge state. An impurity seeding experiment was conducted using the Xe gas puff. In theexperiment, LHD plasma was ignited using the electron cyclotron heating system, while
Negative-ion-based Neutral Beam Injection (N-NBI) #1-3 was 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 wavelength regions. The detailed spectral analysis ofmeasured Xe-ions was performed to validate the theoretical collisional data and CR model
calculations. The CR model calculation included various population transfer kinetic processes
among the fine structure levels of the considered Xe-ion. Detailed atomic structure andcollision calculations were performed for the excitation energies, oscillator strengths, wave
functions, and their cross-sections for various fine structure transitions from the ground stateand excited states to the other fine structure levels using the Flexible Atomic Code (FAC) [3].
Further, these calculated data incorporated into the CR model to solve the kinetic rate balance
equations. Theoretical synthetic spectrum was generated through the population of theconsidered fine structure levels of the Xe-ion. The comparison of theoretical spectra with theLHD-measured spectra validated the atomic structure and collision data calculations
prominent for spectroscopic diagnostics of future fusion plasma experiments in different
tokamak devices.
References[1] A Kallenbach et al, Plasma Phys. Control. Fusion 55, 124041 (2013).
[2] D. Lu et al, Nuclear Fusion 63, 056002 (2023).
[3] M. F. Gu, Can. J. Phys. 86, 675 (2008).