First achievement of high poloidal beta scenario with KSTAR-like constraints on DIII-D

The high poloidal beta (β_P) scenario, recognized as a promising solution for achieving steady-state operation in future fusion devices, has been well established in DIII-D. Recently, initiatives have been taken to demonstrate its feasibility for long-pulse operation in a tungsten environment like KSTAR. As an initial step towards this goal, a collaborative DIII-D-KSTAR team was formed to conduct experiments during the FY24-25 campaign aimed at establishing a high-β_P scenario with KSTAR-like constraints. These constraints include considerations such as the latest plasma shape optimized for a new W-divertor, limited I_P ramp-up rates, and restrictions on auxiliary heating.

The initial experimental results showed that achieving and sustaining a high qmin early in the discharge, a critical element for accessing high-β_P regime, was challenging. Consequently, achieving a large radius ITB formation was initially unsuccessful. However, through optimizations in plasma shape, density, and beta evolutions, and in heating power waveforms, high-performance high-β_P plasmas with ITB at large radius (ρ~0.7), β_N~3.0, H_98y2~1.5, and ƒ_GW~0.8, were eventually achieved. In the presentation, additional improvement strategies will be discussed through more detailed analysis.