Reduced ELM heat loads from increased magnetic field-line length in snowflake configurations

A major concern for fusion devices is the temperature rise of bounding material surfaces from plasma energy exhaust. For short bursts of energy deposition, as from edge-localized modes (ELMs), the temperature rise scales as the total energy deposited divided by the square root of the burst duration, T$_{b}$. The time T$_{b}$ is known to depend on electron and ion convective and conductive transport along the field line, electron and ion collisional equilibration, and radiative losses. The conduction time scales as the field-line length, L, whereas the conduction time scales as L$^{2}$. The snowflake configuration naturally has a much larger L than the conventional X-point divertor, thus yielding larger T$_{b}$, and reduced surface temperature rise. The quantitative impact for the snowflake is presented through the comparison of 3 models: 2-point analytic scaling, 1D along a field line, and 2D including full snowflake tokamak geometry.