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| Home > Publications database > Spectroscopic characterization of boronizations in Wendelstein 7-X |
| Abstract | FZJ-2021-01435 |
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2021
Abstract: Spectroscopic characterization of boronizations in Wendelstein 7-X S. Seredaa*, S. Brezinseka, E. Wanga, T. Barbuib, R. Brakelc, B. Buttenschönc, A. Goriaevd, M. Jakubowksic, R. Königc, M. Krychowiakc, Y. Lianga, D. Naujoksc, L. Rudischhauserc, H. Viebkec, T. Wautersd, Y. Weie, V. Wintersc and the W7-X team aForschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung – Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), Jülich, Germany bPrinceton Plasma Physics Laboratory, Princeton, NJ 08540, United States of America cMax-Planck-Institut für Plasmaphysik, Greifswald, GermanydLaboratory for Plasma Physics, LPP-ERM/KMS, B-1000 Brussels, Belgium, Trilateral Euregio Cluster (TEC) Partner eSouthwestern Institute of Physics, Chengdu, People’s Republic of Chinas.sereda@fz-juelich.deThe last experimental campaign of the Wendelstein 7-X stellarator was performed with the passively cooled graphite test divertor unit (TDU) and the stainless steel walls. In this configuration oxygen and carbon were the main low-Z plasma impurities preventing reaching high plasma densities in the machine. To solve this challenge a set of three boronizations [1] have been applied in a helium glow discharge with 10% diborane.The boronization has resulted in a significant reduction of oxygen (more than one order of magnitude) and carbon (a factor of 4) yields at the TDU strike line location. This change is characterized by an overview spectroscopy system with a wide wavelength range (350 – 1100 nm [2]) allowing simultaneous observation of line emission of the neutrals and the ions of interest (BII, CI, CII, OI, hydrogen Balmer lines). Together with the divertor Langmuir probes in this region it allows deduction of the source particle fluxes. Furthermore, photon fluxes from the filterscope system [3] aiming at the stainless steel wall and equipped with the CIII narrow band filter show a decrease in carbon fluxes after the boronization. These observations prove that oxygen was also an important problem for carbon erosion due to its chemical reactivity with oxygen.In addition, the spectroscopic camera system observing complete TDU module and equipped with the narrowband filters for carbon and hydrogen Balmer lines is used to study influence of boronizations on the fuel recycling. The big observation area of the system provides informatio on the influence of the boronizations on the carbon erosion pattern at TDU. [1] J. Winter, et al., J. Nucl. Mater. (1989) 713-723[2] Y. Wei, et al., AIP Advances (2018) 085011[3] L. Stephey, et al., Phys. Rev. Lett. (2016) 025002This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.
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