Experimental study on boron distribution and transport at plasma-facing components during impurity powder dropping in the Large Helical Device

Kawate, Tomoko; Ashikawa, N.; Goto, Motoshi; Oishi, T.; Kawamoto, Y.; Toyoda, H.; Shoji, M.; Kawamura, Gakushi; Masuzaki, S.; Nespoli, Federico; Gilson, E. P.; Lunsford, Robert; Suzuki, Chihiro; Nagy, A.; Gates, David

doi:10.1088/1741-4326/ac9ac6

Title: Experimental study on boron distribution and transport at plasma-facing components during impurity powder dropping in the Large Helical Device

Journal Article · Thu Nov 03 00:00:00 EDT 2022 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/ac9ac6· OSTI ID:1905782

^[1]; Ashikawa, N. ^[1];

^[1]; Oishi, T. ^[1]; Kawamoto, Y. ^[2]; Toyoda, H. ^[3]; Shoji, M. ^[1];

^[1];

^[4]; Gilson, E. P. ^[4];

^[4];

^[1]; Nagy, A. ^[4];

^[4]

National Institute for Fusion Science, Toki (Japan); Graduate University for Advanced Studies (SOKENDAI), Toki (Japan)
National Institute for Fusion Science, Toki (Japan)
National Institute for Fusion Science, Toki (Japan); Nagoya Univ. (Japan)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Toward real-time wall conditioning, impurity powder dropping experiments with boron powder were performed in the 22nd experimental campaign of the Large Helical Device. To examine the deposition and desorption process of boron, we focus on boron hydride (BH) molecules which presumably populate near plasma-facing components. We performed spatially-resolved spectroscopic measurements of emission by boron ions and BH molecules. From the measurement, we found that BH and B⁺ were concentrated on the divertor viewing chord, which suggest boron deposition in the divertor region. By comparing Hγ emissions with and without boron injection, neutral hydrogen shows uniform reduction in the SOL region, whereas less reduction of neutral hydrogen is confirmed in the divertor region. Although emissions from BH and B⁺ increased linearly, emissions by B0 and B4⁺ became constant after the middle of the discharge. Continuous reduction of carbon density in the core plasma was confirmed even after B⁰ and B⁴⁺ became constant. The results may show reduction of hydrogen recycling and facilitation of impurity gettering by boron in the divertor region and thus effective real-time wall conditioning.

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Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 1905782

Journal Information:: Nuclear Fusion, Vol. 62, Issue 12; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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