Abstract
Small current modulations in a subset of DIII-D I-coils were used in RMP ELM suppression experiments at ITER-like conditions (shape, collisionality, RMP spectrum) to control position of the divertor particle and heat fluxes. Qualitative agreement was found between measured HFS particle flux striations and modeling of magnetic footprints with and without ideal MHD plasma response. However, the radial separation of the particle flux striations is 4-7x larger than the modeled splitting. Striations are generally not observed in the divertor heat flux to the inner strike point in RMP ELM suppression at ITER-like conditions; this is understood to be due to an increase in the volumetric carbon radiation in the inner divertor which washes out the striations in the heat flux to the inner strike point. This suggests that radiative divertor operations in ITER may avoid striated peaks. The divertor target plate heat flux can be reduced 2–3x, with a 60% radiated power fraction, by establishing a narrow radiating mantle between 0.95 ≤ Ψ' ≤ 1. This is achieved without the loss of ELM suppression by using neon or argon injection into the main chamber. These radiating mantle discharges show for the first time that ELM suppression can be maintained over a wide range of pedestal collisionalities (0.1 < 𝜈+∗ < 1.1) with only a modest increase in the line average electron density.
