Characterize SVR Peeling-Ballooning Boundary through Shape Modifications and Front End Development for SuperH Channel Access

2025 Research Campaign, Thrust: Shape Rise Divertor

Purpose of Experiment

The Shape and Volume Rise (SVR) project at DIII-D involved the removal of an in-vessel cryopump and modifying the divertor baffling structures with the goal of enabling tokamak plasma equilibrium shapes with larger volume, elongation and triangularity. These shape changes are predicted to enable a significant increase in confined plasma pressure. The primary goal of this experiment is to allow access to larger volume plasmas at increased triangularity with divertor pumping for density control. Integrated pedestal modeling with EFIT, ELITE and SOLPS predict more Fusion Power Plant (FPP) relevant pedestal conditions can be achieved combining low pedestal collisionality with high neutral opacity in high density, high plasma current, strongly shaped super-H-mode discharges. The primary objectives of this experiment will be to 1) Develop a plasma scenario at high shape and volume that accesses the Super H-mode (SH) channel on the peeling-limited pedestal stability boundary: RMP ELM mitigation or suppression or QH-mode operation may be required due to transient events during channel initial navigation into the SH channel, 2) Optimize plasma shape and q95 for pedestal performance and explore trade-offs between pedestal and divertor performance (e.g. elongation versus divertor leg length), and 3) Identify and characterize limits for operation of a low collisionality pedestal in high density conditions.