Edge Physics Issues In A Burning Plasma Experiment

One of the key issues in the design of a burning plasma experiment is to find suitable plasma facing components (PFC). We have investigated a variety of plasma edge conditions ranging from full plasma contact yielding high heat flux conditions (attached mode) to impurity addition that causes radiative dispersal of the plasma power and lower heat flux (detached mode). The predicted peak heat flux on the divertor is 5 to 25 MW/m2. For all of the cases investigated the edge plasma region is led to a region far from the core plasma (divertor operation). The inner leg of the divertor easily enters detached mode due to hydrogen radiation while impurities have to be added to the outer divertor to achieve detachment. Particle diffusivity and thermal conductivity of the edge plasma are derived from experiments on existing fusion machines. The models include ionization, radiation and recombination effects on both plasma ions and impurities. Neutral atom generation and transport in the edge region are included. Magnetohydrodynamic effects in the core plasma near the edge can cause Edge Localized Modes that cause periodic fluctuations in the particle and heat flux to the divertor plates. We will discuss the impact of the variety of physics operating conditions on the PFC design.