Open AccessReal-time wall conditioning by controlled injection of boron and boron nitride powder in full tungsten wall ASDEX Upgrade
Author(s) -
A. Bortolon,
V. Rohde,
R. Maingi,
E. Wolfrum,
R. Dux,
A. Herrmann,
R. Lunsford,
R. M. McDermott,
A. Nagy,
A. Kallenbach,
D. K. Mansfield,
R. Nazikian,
R. Neu
Publication year - 2019
Publication title -
nuclear materials and energy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.324
H-Index - 25
ISSN - 2352-1791
DOI - 10.1016/j.nme.2019.03.022
Subject(s) - asdex upgrade , collisionality , boron nitride , boron , tungsten , materials science , tokamak , limiter , divertor , metallurgy , plasma , nuclear engineering , composite material , nuclear physics , physics , electrical engineering , engineering
In ASDEX Upgrade with full-tungsten wall, boronization is an important tool to control tungsten sources and allow reliable operation at low collisionality. The duration of the beneficial effects is limited by the erosion of the boron layer, in particular on the tungsten ion-cyclotron antenna limiters. We report results from experiments exploring injection boron-rich powders in tokamak plasmas as a way to replenish boron coating and extend the lifetime of boronization effects. Pure boron and boron nitride powders were introduced gravitationally in plasma discharges at rates up to 60 mg/s for durations up to 3 s. Boron injection with cumulative amounts >100 mg appeared to improve wall conditions similarly to boronization, with indications of reduced influx of oxygen and tungsten from the antenna limiter. Moreover, cumulative injection of 340 mg of B appeared sufficient to enable successful execution of low collisionality scenarios critically relying on freshly boronized walls.
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