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P: Fachverband Plasmaphysik

P 18: Postersitzung

P 18.101: Poster

Donnerstag, 21. März 2019, 16:30–18:30, Foyer Audimax

Conceptual system design study of an NNBI beamline for DEMO — •Giuseppe Starnella, Christian Hopf, Niek den Harder, and Ursel Fantz — Max-Planck-Institut für Plasmaphysik, Garching bei München, Germany

Neutral Beam Injection (NBI) is one of the heating and current drive (H&CD) systems considered for DEMO. The DEMO design is in a pre-conceptual phase, meaning that many options are under investigation and, therefore, the requirements for the NBI development are still not clear. In any case, the commercial viability of Fusion Power Plants (FPP) depends on maximizing the wall-plug efficiency. The NBI wall-plug efficiency is currently limited to about 27% on ITER, mostly due to the low efficiency of the gas neutralization. Hence, increasing the neutralization efficiency is compulsory.

Plasma neutralization is one of the alternatives that we take into consideration: a plasma is used in place of the neutral gas, in which the electrons more readily strip the negative ions. The plasma inside the neutralizer is created by the negative ion beam as it passes through the neutral gas. The optimum target thickness to obtain the maximum neutralization efficiency is studied for different geometries as well as the ion trajectories in presence of the magnetic cusp field that is applied to confine the plasma.

Another technological solution is the Energy Recovery (ER): after neutralization, the energy of the residual ions is recovered by separating, decelerating and collecting them on different collectors. We present a first conceptual design for the integration of an ER system.