Description
This work presents a new integrated study of hydrogen isotope effects on scrape-off layer (SOL) transport, divertor performance, and pedestal fueling combining dedicated DIII-D H-mode experiments together with SOLPS-ITER simulations with full drifts. Matched H and D discharges were specifically designed to isolate isotope effects providing a systematic comparison of pedestal structure and divertor detachment behavior. Increasing isotope mass significantly reduces divertor particle and heat fluxes prior to detachment, with particle fluxes decreasing from H to D. Detached conditions occur at ~15% higher upstream density in H after SOLPS-ITER modeling constrained by experiment indicates that carbon sputtering, rather than neutral mean free path effects, is the primary driver of the observed isotope dependence of detachment access. To isolate the fundamental mass dependence from impurity effects, simulations are extended to pure H, D, and T plasmas with both carbon and tungsten walls. The isotope effect is shown to arise primarily from parallel momentum balance: while pressure and electric-field forces are nearly identical across isotopes, heavier ions experience lower acceleration due to increased inertia, producing slower SOL parallel flows and reduced convective transport. From H to T, target particle fluxes decrease by nearly a factor of two, while divertor heat fluxes decrease by ~10% for each increase in isotope mass. These results provide a comprehensive, experimentally validated predictions of isotope effects for DT operation in future fusion devices.