Unified scaling of divertor heat flux widths across confinement regimes to reactor-relevant magnetic fields in the Alcator C-Mod tokamak*

New data from Alcator C-Mod have extended the range of heat flux measurements and scalings to poloidal magnetic fields above ITER-level (1.2 T). An international database indicated that λ_q scaled inversely with the poloidal magnetic field (B_p) up to 0.8 T and had no other significant dependencies. Alcator C-Mod has been the only diverted tokamak capable of operating at reactor-level B_p. A major focus of the final campaign on Alcator C-Mod was to characterize λ_q over a wide range of conditions, utilizing a unique array of heat flux sensors with unprecedented spatial resolution and heat flux dynamic range. The heat flux width scaling is found to extend up to B_p~1.3 T in H-mode. Looking across confinement regimes (L-, I-, and H-modes) we find the remarkable result that λ_q exhibits a unified dependence on core volume-averaged core plasma pressure. Within a standard deviation of ~20%, the heat flux width in any of the C-Mod plasmas studied is proportional to the inverse square root of core volume-averaged core plasma pressure. These results stand in stark contrast to recent simulations, indicating ~10 times wider heat flux width for ITER.