Abstract Details
Abstracts
Author: Robert W. Brzozowski
Requested Type: Consider for Invited
Submitted: 2024-03-29 16:29:07
Co-authors: T.Stoltzfus-Dueck
Contact Info:
Princeton Plasma Physics Laboratory
100 Stellarator Rd
Princeton, New Jersey 08540
United States of Ame
Abstract Text:
Toroidal rotation in a tokamak plasma plays a crucial role in mitigating instabilities like resistive wall modes and stabilizing the plasma. Unlike present-day tokamaks, neutral-beam injection (NBI) won’t be able to effectively drive rotation in ITER. Despite intensive theoretical investigation, mysteries remain, such as counter-current shifts in intrinsic rotation with increasing density in TCV [Duval et al PPCF 49: B195 (2007)] and when transitioning to the unfavorable drift configuration in C-mod L-mode plasmas [LaBombard et al NF 44: 1047 (2004)]. Such shifts can be dangerous when an NBI torque does not dominate, as in ITER, since they oppose the typically co-current edge intrinsic rotation. These behaviors may be explained by the coupling of scrape-off layer (SOL) ion flows to the edge intrinsic ion rotation via neutrals. Neutrals that charge exchange (c.x.) in the SOL gain parallel momentum characteristic of the local ions. Since the neutrals are insensitive to the electromagnetic fields, their cross-field mobility lets them transport this momentum into the confined plasma. Strongly poloidally asymmetric neutrals, as seen on DIII-D [Rosenthal et al Nucl. Fusion 63: 042002 (2023)], could reintroduce the signed momentum of the local near- sonic SOL outflows into the pedestal. We present an extension of the modulated transport model [Stoltzfus-Dueck PoP 19: 055908 (2012)], a simple self-consistent model for the edge intrinsic rotation resulting from turbulent transport coupled to passing ion drift orbits. We show that neutrals coupled to the edge ions in the short c.x. step limit cannot drive a significant toroidal rotation within a self-consistent treatment of the edge for realistic parameters. However, the neutrals are able to more significantly alter the rotation for such parameters when finite-length steps are maintained. Only with this generalization can the neutrals effectively couple the strong transport-driven SOL-flow momentum to the pedestal rotation
Comments:
This abstract is suited for the following solicited topics in order:
1)Physics of the plasma edge
2)Plasma Transport
3)Analytic methods for modeling plasmas