Sixth IAEA Technical Meeting on Fusion Data Processing, Validation and Analysis

Benchmarking Fusion Plasma Diagnostics: Analysis of Experimental W and Mo X-ray Data from EBIT Resolves Plasma Speed Contradiction

11 Sept 2025, 11:40

25m

Auditorium Hall HGX 102 (Guanghua Twin Tower) (Fudan University, Shanghai, China)

Oral (Regular) Uncertainty Propagation, Verification and Validation Uncertainty Propagation, Verification and Validation

Speaker

YANG YANG (Fudan University)

Description

Tungsten will be a strong candidate of the material for ITER divertor. All Spectroscopies related to tungsten were then become highlight fields. Meanwhile Molybdenum is an impurity that are not be neglected in many Tokamak plasma, and thus be used for diagnostic widely.
The x-ray transitions from W45+,46+ ions and Mo32+ in the 5.19–5.26Å wavelength range that are relevant as a high-temperature tokamak diagnostic, in particular for JET in the ITER-like wall configuration, have been studied in this work with an electron beam ion trap which produces and confines highly charged ions for disentangle studies of plasma atomic processes.
Tungsten spectra were measured at the upgraded Shanghai Electron Beam Ion Trap operated with electron-beam energies from 3.16 to 4.55 keV. High-resolution measurements were performed by means of a flat Si 111 crystal spectrometer[1] quipped by a CCD camera. The experimental wavelengths were determined with an accuracy of 0.3–0.4 mÅ[2]. All measured wavelengths were compared with those measured from JET ITER-like wall plasmas and with other experiments and various theoretical predictions including COWAN, RELAC, multi-configurational Dirac-Fock (MCDF), and FAC calculations. To obtain a higher accuracy from theoretical predictions, the MCDF calculations were extended by taking into account correlation effects (configuration-interaction approach). And Mo32+ spectra in the same region were studied after that. With these very accurate wavelength data, contradiction between theoretical result and measured values was resolved related to impurity transportation speed in the fusion plasma.

Fig. 1 A general scheme of the experimental setup at the upgraded Shanghai EBIT.

Fig 2. Tungsten (W45+ and W46+) and molybdenum (Mo32+) x-ray lines observed in the spectrum measured at JET (shot #85909) at 𝑇𝑒≈3.9 keV and 𝑛𝑒≈3.2×10^19 m−3.

References
[1] Y. Yang, J. Xiao, D. Lu, Y. Shen, K. Yao, C. Chen, R. Hutton, and Y. Zou, A high precision flat crystal spectrometer compatible for ultra-high vacuum light Source, REVIEW OF SCIENTIFIC INSTRUMENTS 88 113108 (2017)
[2] J.Rzadkiewicz, Y. Yang, K. Koziol, M. G. O’Mullane, A. Patel, J. Xiao, K. Yao, Y. Shen, D. Lu, R. Hutton, Y. Zou, and JET Contributors, High-resolution tungsten spectroscopy relevant to the diagnostic of high-temperature tokamak plasmas, PHYSICAL REVIEW A 97 052501 (2018)