A simple model of intrinsic rotation in high confinement regime tokamak plasmas

Abstract

A simple unified model of intrinsic rotation and momentum transport in high confinement regime ͑H-mode͒ tokamak plasmas is presented. Motivated by the common dynamics of the onset of intrinsic rotation and the L-H transition, this simple model combines E ϫ B shear-driven residual stress in the pedestal with a turbulent equipartition pinch to yield rotation profiles. The residual stress is the primary mechanism for buildup of intrinsic rotation in the H-mode pedestal, while the pinch drives on-axis peaking of rotation profiles. Analytical estimates for pedestal flow velocities are given in terms of the pedestal width, the pedestal height, and various model parameters. The predicted scaling of the toroidal flow speed with pedestal width is found to be consistent with the International Tokamak Physics Activity database global scaling of the flow speed on-axis with the total plasma stored energy.

Transport of parallel momentum by toroidal ion temperature gradient instability near marginality

“…We'll address the residual stress, which can be crucial in more general context [42,43], in the future.…”

On the efficiency of intrinsic rotation generation in tokamaks

“…In the fusion community, some attempts to characterize flow generation in plasmas as the result of the action of a thermodynamic engine have been discussed. 15,16 In those, flow generation is treated as analogous to the work ͑power, more precisely͒ which can be extracted from the exchange of heat between hot and cold parts of plasmas, i.e., the heat flux driven by ٌT. However, these discussions have not given a systematic calculation for the figure of merit of the engine.…”

Core momentum and particle transport studies in the ASDEX Upgrade tokamak

“…Although our theoretical understanding of momentum transport has developed appreciably [17,18,19,20,21,22,23,24,25,26], validation of momentum theory through comparison to experiment is still in its early stages [27,28,29,30,31,32,33,34,35]. In particular, our understanding of intrinsic momentum fluxes remains largely empirical [36,37,38,39,40,41,42,43] and detailed comparison between theoretically predicted residual stress mechanisms and experimental observations of intrinsic rotation remains an open area of research.…”