Abstract Details
Abstracts
Author: David R Hatch
Requested Type: Consider for Invited
Submitted: 2024-03-29 16:11:22
Co-authors: M. Kotschenreuther, S. M. Mahajan, C. Stevens, G. Merlo, P-Y Li
Contact Info:
Institute for Fusion Studies, UT Austin
2515 Speedway C1500
Austin, Texas 78712
USA
Abstract Text:
One of the most critical challenges in developing a tokamak or stellarator based fusion pilot plant (FPP) lies in simultaneously satisfying the requirements of plasma confinement and plasma exhaust. These are often in conflict, arising from the need to reconcile the extremely high fusion temperatures within the core plasma (>10keV) with conditions that are sustainable for plasma-facing components. In this presentation, we propose a strategy for core-edge integration leveraging low scrape-off layer (SOL) density and high SOL temperature to significantly enhance confinement. We begin by presenting empirical evidence from the latest International Tokamak Physics Activity (ITPA) H-mode database, which reveals a naturally occurring high-confinement regime at low separatrix density. The data suggests that this favorable confinement results largely from transport dynamics, with a smaller (also favorable) effect attributable to magnetohydrodynamic (MHD) stability limits. Following this, we describe a theoretical (gyrokinetic) framework for understanding transport barriers, which is consistent with these empirical observations. This framework exploits two constraints, free energy and ambipolarity, to explain wide-ranging transport barrier phenomena, which we investigate using the GENE code. Building on this theoretical foundation, we apply reduced models for pedestal transport to predict the response of pedestal temperature profiles to the pedestal density, demonstrating the potential for significant improvements in confinement. Tailoring of the density profiles can likely substantially improve confinement in burning plasma conditions. Lastly, we touch on a novel divertor concept, the super-XT divertor, which could facilitate the desired parameter regime in an FPP.
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