Active conditioning of asdex upgrade tungsten plasma-facing components and discharge enhancement through boron and boron nitride particulate injection

R. Lunsford, V. Rohde, A. Bortolon, R. Dux, A. Herrmann, A. Kallenbach, R. M. McDermott, P. David, A. Drenik, F. Laggner, R. Maingi, D. K. Mansfield, A. Nagy, R. Neu, E. Wolfrum

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31 Scopus citations

Abstract

The injection of boron (B) and boron nitride (BN) powders into ASDEX Upgrade H-mode discharges have demonstrated effective control of tungsten influx in low density/collisionality operational regimes, similar to conventional boronization methods. Sub-mm powder particles are gravitationally accelerated into the upper edge of a lower single null H-mode plasma with a boundary shape roughly conforming to the shape of the poloidal midplane limiters. Visible spectroscopy measurements at one of the outer limiter showed increases in both B and N signal levels, as well as elevated B levels in the divertor, and an increase in total radiated power by greater than a factor of two during BN injection. Globally the BN injection improved energy confinement by 10%-20%, associated with improvements in pedestal performance similar to gaseous N injection. Following conditioning discharges with B powder injection, three low gas-fueling discharges with magnetic perturbations for ELM suppression were successfully conducted. These first results suggest that the application of B containing powders can be used to both improve plasma performance in real-time, and to improve overall wall conditions for subsequent discharges.

Original languageEnglish
Article number126034
JournalNuclear Fusion
Volume59
Issue number12
DOIs
StatePublished - 14 Oct 2019
Externally publishedYes

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