Influence of magnetic field strength on scrape-off layer drift effects in W7-X

E×B drifts play an important role in the island divertor scrape-off layer (SOL) employed by the W7-X stellarator, altering plasma flows and creating asymmetric strike line shifts between upper and lower divertors. To understand how drift effects scale with magnetic field strength and aid divertor design for future high-field stellarators, plasmas with different field strengths (1.8 and 2.5 T) but matched control parameters (line-averaged density and heating power) are compared. These experiments are enabled by the recent development of third harmonic electron cyclotron resonance (X3) heated scenarios for 1.8 T operation. The poloidal E×B velocity v_E,θ inferred just outside the last closed flux surface by gas puff imaging is systematically higher at 1.8 T, in line with a 1/B scaling. Coherence imaging spectroscopy measures slight shifts of the parallel flow v_‖ stagnation regions between 1.8 and 2.5 T, which based on a 1D simple SOL model indicates a stronger influence of v_E,θ on v_‖ at lower field. In contrast to these observations in the upstream SOL, the carbon radiation distribution near the divertor exhibits only minor changes with field strength. This suggests the upstream drift velocity may scale differently than the effects of the drift on divertor strike line positions.