Berlin 2014 – scientific programme
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P: Fachverband Plasmaphysik
P 2: Magnetic Confinement I
P 2.2: Topical Talk
Monday, March 17, 2014, 11:00–11:25, SPA HS202
High density operation using pellet fuelling on ASDEX Upgrade — •P.T. Lang1, M. Bernert1, L. Casali1, R. Fischer1, O. Kardaun1, G. Kocsis2, M. Maraschek1, A. Mlynek1, B. Plöckl1, F. Ryter1, T. Szepesi2, G. Tardini1, H. Zohm1, and ASDEX Upgrade Team1 — 1MPI für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany — 2Wigner RCP, RMI, P.O.Box 49, H-1525 Budapest-114, Hungary
Operating a future fusion reactor at high central densities is needed to maximise fusion power. However, an empirical density limit called Greenwald density nGw is encountered for gas fuelling. Energy confinement degradation takes place already at about 0.8 × nGw. This limitation can be overcome by injecting mm size pellets of frozen Deuterium. The reason is that the pellets provide a particle source inside the plasma region where a critical density exists. An advanced launching system for efficient pellet fuelling has been developed and is applied at the ASDEX Upgrade tokamak. With this system reliable and reproducible high density operation was demonstrated. Core densities have been achieved up to 1.7 × nGw in steady state, and up to 4 × nGw transiently, while keeping the edge density always below nGw. As an additional benefit, edge localized mode activity, responsible for intense transient heat loads to plasma facing components, can be mitigated in the high density regime. By extending the accessible plasma density range beyond 0.85 × nGw, the conventional energy confinement scaling no longer applies. As this regime is of special interest for the design of future larger tokamak devices, a more refined scaling has been derived.