Edge PhysicsEdge Physics

As well as needed to understand what is occuring within a fusion plasma to ensure stability and therefore a sustained reaction it is also essential to understand what is occuring at the edge of the fusion plasma, where it is closest to the reactor walls.  The plasma-wall interaction has to be carefully controlled to keep the plasma pure, maintain the quality of the plasma and the purity of the fuel being used.  Any interaction between the plasma and the wall can potential contaminate the plasma with "heavy ions" which reduce the efficiency of the plasma and can interfere with the fusion process.

Plasma confinement can Cutaway of ITER Edgenever be ideal, not least as it is necessary to flush the plasma flame of ash (Helium) and to replace the fuel (Hydrogen). This already sets a critical lower bound to the level of plasma surface interaction needed: the plasma core is connected to the vessel walls by a magnetically non-confined outer region, via which plasma throughput has to be maintained and in which plasma surface interactions lead to powerful exchange of matter between the plasma and the solid container. The sheer complexity of this edge physics demands multi-scale, multi-physics modelling.  In particular, very near to the solid surfaces a self-consistent description for electrostatic fields and even full gyro motion resolved kinetics is essential for the dynamics of the system, the plasma chemistry, and to provide consistent boundary conditions.,

Addressing "near surface plasma effects", this work looks to provide connections between the "core" and "upstream" plasma simulations with gyro-kinetic codes on the one hand, and computational material science on the other. Ultimately, this could provide the computational bridge leading to mutually consistent, integrated global numerical tokamak approaches.