New insights on scrape-off layer plasma turbulence

Paolo Ricci

École Polytechnique Fédérale de Lausanne

Friday, April 27, 2018

3:00pm

NW17-218

PSFC Seminars

One of the greatest uncertainties in the success of ITER and future fusion reactors is related to the turbulent dynamics of the fusion fuel in the scrape-off layer (SOL). The plasma behavior in this region governs the overall confinement of a tokamak, regulates the impurity dynamics and the level of fusion ashes, and determines the heat load to the tokamak vessel walls -- a showstopper for the whole fusion program if material requirements cannot be met. With the goal of improving our understanding of plasma turbulence in the SOL, the GBS code has been developed in Lausanne during the past few years.  By solving the drift-reduced Braginskii equations coupled to a kinetic equation for the neutrals, GBS evolves self-consistently the SOL dynamics as it results from neutral recycling, turbulent transport, and plasma losses at the vessel. GBS simulations have led, for example, to the identification of the instabilities driving SOL turbulence and to a first-principles estimate ofthe turbulence saturation amplitude and of the SOL pressure scale length. We will present our simulation and theoretical results, as well as their comparison with experimental measurements from several tokamaks worldwide.