Fusion for Energy

The gas in fusion reactors is in the 4th state of matter, the plasma state, where electrons are no longer bound to nuclei. In tokamaks like ITER, the international facility presently under construction at Cadarache (France), the plasma is confined by magnetic fields of a few Tesla. From the plasma physics point of view, three critical issues are identified on the route towards a Fusion based reactor: (i) ensuring the lifetime of the divertor – which collects particle and heat out fluxes, (ii) improving the quality of the energy confinement within the magnetic configuration, and (iii) preserving the purity of the fuel with respect to impurities and helium ashes. The long term objectives target these three major problems by first principle simulations, which provide support to experiments in this quest:

• To predict and optimise confinement properties of tokamak plasmas through 5D gyrokinetic simulations of core turbulent and collisional transport in realistic geometries. A broad spectrum of scales is needed for a self-consistent treatment of the problem;
• To predict the power threshold for the Low to High confinement regime via 3D fluid simulations of turbulent transport across the last closed magnetic flux surface, which separates the confined and unconfined regions of tokamak plasmas. This includes divertor physics and plasma-wall interactions;
• To model edge quasi-periodic relaxation events called "ELMs" by means of 3D Magneto Hydro Dynamics (MHD) simulations, in view of predicting their impact on the divertor plates, of understanding the underlying physics and developing strategies for their mitigation;
• To predict the sources & transport of neutrals by means of 1D to 3D fluid simulations coupled to a Monte-Carlo code.