Hannover 2016 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 21: Magnetic Confinement II
P 21.4: Vortrag
Donnerstag, 3. März 2016, 12:25–12:40, b302
Impact of Lithium on the plasma performance in the all-metal-wall tokamak ASDEX Upgrade — •P.T. Lang1, R. Moreno Quicios1, R. Arredondo Parra1, B. Ploeckl1, R. Maingi2, D.K. Mansfield2, A. Diallo2, R. McDermott1, R. Neu1, E. Wolfrum1, and ASDEX Upgrade Team1 — 1MPI für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany — 2Princeton Plasma Physics Laboratory, Princeton, NJ 08543, USA
Several tokamaks reported improvement in key plasma parameters concurrent with the presence of lithium in the plasma. At ASDEX Upgrade explorative experiments have been performed to find out if such effects can be observed when operating with an all-metal-wall. A gas gun launcher was developed capable to inject pellets containing about 1.6 × 1020 Li atoms at 2 Hz. The speed of about 600 m/s is sufficient to achieve core penetration and to create a homogeneous Li concentration of up to 10 %. With a typical sustainment time on the order of 100 ms, only transient Li presence without any pile up was achieved. Deposition of Li on plasma facing components, which remained for several discharges after injection, was observed. This short lived wall conditioning showed beneficial effects during plasma start-up. However, the accompanying surface contamination negatively impacted some diagnostics. The Li impact on the confinement was investigated in a dedicated plasma scenario with a proven sensitivity to nitrogen and helium. In phases with N seeding enhancing the confinement by about 30 %, Li injection resulted in a very modest, transient loss of confinement (about 5 %). No Li impact was found for pure Deuterium plasmas.