Intrinsic rotation reversal, non-local transport, and turbulence transition in KSTAR L-mode plasmas

Shi, Yuejiang; Kwon, J.M.; Diamond, P. H.; Ko, W. H.; Choi, M.; Ko, S. H.; Hahn, S.H.; Na, D. H.; Leem, J.; Lee, J. A.; Yang, SeongMoo; Lee, K. D.; Joung, M.; Jeong, J.H.; Yoo, J. W.; Lee, W. C.; Lee, J. H.; Bae, Y. S.; Lee, S. G.; Yoon, S. W.; Ida, K.; Na, Y. S.

doi:10.1088/1741-4326/aa6b23

Cited by 31 publications

(36 citation statements)

References 51 publications

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“…By the 80s this optimism subsided when it was found that the energy confinement time saturates [7,9,13,14,17,20,21,22,23,24] above a critical density. This saturated Ohmic confinement (SOC) regime is also remarkably ubiquitous in tokamak operation [25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47]. An early example of both regimes is shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Understanding LOC/SOC phenomenology in tokamaks

et al. 2020

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Phenomenology of Ohmic energy confinement saturation in tokamaks is reviewed. Characteristics of the linear Ohmic confinement (LOC) and saturated Ohmic confinement (SOC) regimes are documented and transformations in all transport channels across the LOC/SOC transition are described, including rotation reversals, "non-local" cut-off and density peaking, in addition to dramatic changes in fluctuation intensity. Unification of results from nearly 20 devices indicates that the LOC/SOC transition occurs at a critical value of the product of the density, edge safety factor and device major radius, and that this product increases with toroidal magnetic field. Comparison with gyro-kinetic simulations suggests that the effects of sub-dominant TEMs are important in the LOC regime while ITG mode turbulence dominates with SOC. 1

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Section: Introductionmentioning

confidence: 99%

Understanding LOC/SOC phenomenology in tokamaks

et al. 2020

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“…These perturbative transport effects have been interpreted as non-local phenomena, requiring explanation outside of the standard local-transport paradigm [2]. Cold-pulses have been conducted on both tokamaks and stellarators (TEXT [3], TFTR [4], Tore Supra [5], RTP [6], ASDEX Upgrade [7], JET [8], LHD [9], HL-2A [10], Alcator C-Mod [11] and KSTAR [12]). In these experiments, a sharp drop in edge electron temperature results from the deposition of neutral particles at the periphery of the plasma, usually via laser ablation.…”

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confidence: 99%

Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

et al. 2018

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A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling of fusion plasmas triggers core electron heating on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. This Letter shows that the steady-state profiles, the cold-pulse rise time, and disappearance at higher density as measured in these experiments are successfully captured by a recent local quasilinear turbulent transport model, demonstrating that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and time scales of cold-pulse experiments in tokamak plasmas.

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“…This observation suggests that the large electron temperature produced by ECH drives the intrinsic toroidal rotation which overcomes the toroidal rotation externally driven by NBI. Later the flow reversal was also found to have a bifurcation and transition phenomena, where the flow reversal can occur by a slight change of plasma parameter in various tokamaks [112][113][114][115][116]. Figure 19 shows the flow reversal of intrinsic rotation observed during the slow density ramp in TCV ohmic discharge (with no external torque) [112].…”

Section: Momentum Transport (Toroidal Flow Reversal)mentioning

confidence: 95%

Bifurcation phenomena in magnetically confined toroidal plasmas

Ida

2020

Advances in Physics: X

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Bifurcation phenomena observed in turbulence and transport, in topology of magnetic field and MHD, and the interplay between turbulence and MHD bifurcation in magnetically confined toroidal plasmas are reviewed. Two types of bifurcation phenomena in turbulent transport are discussed. One is significant change in the magnitude of the diffusion term and the other is a sign flip of non-diffusive term of transport. The bifurcation of diffusion term magnitude causes the transition to a so-called improved mode such as ion-electron root transition, L-mode to H-mode transition, and ITB formation. In contrast, the bifurcation of non-diffusion term sign causes the intrinsic flow reversal, convection reversal of bulk ion, and impurity ions. Two types of bifurcation phenomena in MHD are discussed. One is the bifurcation of static magnetic topology and the other is the bifurcation of MHD instability. The bifurcation of static magnetic topology is observed in between three magnetic topology (nested magnetic flux surface, magnetic island and stochastic magnetic field) in toroidal plasma. The bifurcation of MHD instability is observed as a parity change of MHD oscillation. The bifurcation of the magnetic island states caused by the interplay between turbulence and MHD is also discussed.

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Intrinsic rotation reversal, non-local transport, and turbulence transition in KSTAR L-mode plasmas

Cited by 31 publications

References 51 publications

Understanding LOC/SOC phenomenology in tokamaks

Understanding LOC/SOC phenomenology in tokamaks

Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

Bifurcation phenomena in magnetically confined toroidal plasmas

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